How to analyze a cloud in the sky

Also learn what weather’s coming based on the cloud type

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ThoughtCo / Vin Ganapathy

  • Weather & Climate
    • Understanding Your Forecast
    • Storms & Other Phenomena

    How to analyze a cloud in the sky

    • B.S., Atmospheric Sciences and Meteorology, University of North Carolina

    According to the World Meteorological Organization’s International Cloud Atlas, more than 100 types of clouds exist. The many variations, however, can be grouped into one of 10 basic types depending on their general shape and height in the sky. Thus, the 10 types are:

    • Low-level clouds (cumulus, stratus, stratocumulus) that lie below 6,500 feet (1,981 m)
    • Middle clouds (altocumulus, nimbostratus, altostratus) that form between 6,500 and 20,000 feet (1981–6,096 m)
    • High-level clouds (cirrus, cirrocumulus, cirrostratus) that form above 20,000 feet (6,096 m)
    • Cumulonimbus, which tower across the low, middle, and upper atmosphere

    Whether you’re interested in cloud watching or are just curious to know what clouds are overhead, read on to find out how to recognize them and what type of weather you can expect from each.


    DENNISAXER Photography/Getty Images

    Cumulus clouds are the clouds you learned to draw at an early age and that serve as the symbol of all clouds (much like the snowflake symbolizes winter). Their tops are rounded, puffy, and a brilliant white when sunlit, while their bottoms are flat and relatively dark.

    When You’ll See Them

    Cumulus clouds develop on clear, sunny days when the sun heats the ground directly below (diurnal convection). This is where they get their nickname of “fair weather” clouds. They appear in the late morning, grow, and then disappear toward evening.


    How to analyze a cloud in the sky

    Matthew Levine/Getty Images

    Stratus clouds hang low in the sky as a flat, featureless, uniform layer of grayish cloud. They resemble fog that hugs the horizon (instead of the ground).

    When You’ll See Them

    Stratus clouds are seen on dreary, overcast days and are associated with light mist or drizzle.


    How to analyze a cloud in the sky

    Danita Delimont/Getty Images

    If you took an imaginary knife and spread cumulus clouds together across the sky but not into a smooth layer (like stratus), you’d get stratocumulus—these are low, puffy, grayish or whitish clouds that occur in patches with blue sky visible in between. When viewed from underneath, stratocumulus have a dark, honeycomb appearance.

    When You’ll See Them

    You’re likely to see stratocumulus on mostly cloudy days. They form when there’s weak convection in the atmosphere.


    How to analyze a cloud in the sky

    Seth Joel/Getty Images

    Altocumulus clouds are the most common clouds in the middle atmosphere. You’ll recognize them as white or gray patches that dot the sky in large, rounded masses or clouds that are aligned in parallel bands. They look like the wool of sheep or scales of mackerel fish—hence their nicknames “sheep backs” and “mackerel skies.”

    Telling Altocumulus and Stratocumulus Apart

    Altocumulus and stratocumulus are often mistaken. Besides altocumulus being higher up in the sky, another way to tell them apart is by the size of their individual cloud mounds. Place your hand up to the sky and in the direction of the cloud; if the mound is the size of your thumb, it’s altocumulus. (If it’s closer to fist-size, it’s probably stratocumulus.)

    When You’ll See Them

    Altocumulus are often spotted on warm and humid mornings, especially during summer. They can signal thunderstorms to come later in the day. You may also see them out ahead of cold fronts, in which case they signal the onset of cooler temperatures.

    Sky Machine Learning

    Applying convolutional neural networks to the task of semantic segmentation of (meteorological) clouds.

    Setting up your Environment

    If you have successfully run python scripts on your machine in the past and you are comfortable with your current editor, you may skip this step.

    We recommend downloading and installing git, a version control system that integrates well with github. This will help you download our code and stay up-to-date with bug fixes and other changes. We recommend installing git with the default installation settings if possible.

    If you don’t have python installed on your system, you will need to download and install python on your system. You can get python here. If you’re on Windows, we recommend including Python in your PATH when using the setup wizard.

    Once you have python installed on your system, you will need an integrated development environment (IDE) to make a few code changes specific to your system. We recommend using PyCharm because it has many useful features, is well-documented, and seemlessly integrates with git.

    Whatever environment you decide to use, you will need have the following packages installed prior to running our code: tensorflow, numpy, matplotlib, pandas, pickle, pillow (PIL), keras, time, imageio and scipy.

    Downloading the data

    Our data consists of sky images and and cloud masks from 5/1/2012 to 9/24/2017. The data belongs to, so to obtain it for yourself you will need to follow the following steps:

    1. Log in or create an account with ARM
    2. Go to the Data Discovery page and select the checkboxes next to “tsicldmask C1” and “tsiskyimage”
    3. Proceed to checkout with the data and download as tarred files.
    4. Untar the downloaded files into folders named “CloudMask” and “SkyImage”

    It can take several days for ARM to stage the files for download and the files are several gigabytes altogether. Once your data in downloaded and unpacked into a convenient location, you’re all set.

    Running the Project on Your Machine

    After downloading our code from our repository, open the configuration file ( and set the desired parameters and file paths for your machine. Note that you will have to ensure that “BLT = False” for the code to run properly on your computer.

    Navigate to the file path you have specified in the config file as RAW_DATA_DIR. Then create two new directories named SkyImage and CloudMask and put the skyimage and cldmask tar files in their respective directories. Once the files are organized, running will unpack all of the tarred files into their appropriate subdirectories in CloudMask and SkyImage.

    Once the configuration file is set up, you should be good to go. Now you just need to run the files in the order below:

    1. (Creates directories)
    2. (Separates data file names into different files)
    3. (Cleans up images for training)
    4. (Trains data on selected network architecture)
    5. (Plots data from training)
    6. (Generates images of the network output)
    7. (Computes fractional sky coverage)
    8. (Creates graphs based on fractional sky coverage)

    Note that you can change various training-specific parameters in and run several times without needing to run the preprocessesing tasks again. For example – once the preprocessing tasks are done and you’ve trained the network once, you may wish to try out a different learning rate or train for a different number of batches. You can do this simply by modifying EXPERIMENT_LABEL in so that your existing network is not overwritten, and then change LEARNING_RATE and NUM_TRAINING_BATCHES to your desired values. Once these changes have been made, running will begin training a new network with your new configurations.


    Using deep convolutional networks to analyze photographs of clouds in the sky.

    News from the Columbia Climate School

    New Project Will Analyze Clouds to Make Future Climate Less Nebulous

    How to analyze a cloud in the sky

    Because low clouds influence how much sunlight reaches the Earth’s surface, they will play an important role in determining how hot the planet gets under climate change. A new project at Columbia University is helping to determine whether low cloud cover will increase or decrease under climate change, so that projections for future warming will be more accurate. This photo shows shallow cumulus clouds — one of the cloud types that will be studied. Photo: Glg/Wikimedia Commons

    They may be mere swirls of dust and mist, but clouds have proven to be a hefty challenge for climate projections. We know that humans are making the planet hotter, but it is difficult to predict exactly how bad things will get; climate scientists think temperatures could climb by anywhere between a relatively mild 1.5 degrees Celsius and a devastating 4.5 degrees by the end of the century. Clouds are about 50 percent of the reason that range is so large, because scientists aren’t sure how clouds will behave on a hotter planet — if climate change decreases cloud cover, more sunlight will reach the earth’s surface and temperatures will rise higher. Conversely, if cloud cover increases, they could block sunlight and help to alleviate rising temperatures.

    A new project, led by Gregory Cesana from the Center for Climate Systems Research at Columbia University’s Earth Institute, will unravel the mysteries of how low clouds (less than 3 kilometers from the ground) respond to climate change, to help narrow the range of how much warming we can expect as CO2 continues to rise.

    Low clouds, particularly those in the tropics, are one of the main culprits behind the cloud-related uncertainties in climate projections. This is due to the fact that the tropics (the areas between 30 degrees north and south of the equator) receive the largest amount of solar radiation, and because the low clouds cover a large portion of these areas, said Cesana. His work will project the future low cloud cover not only in the tropics, but also the extratropics, which extend nearly to the polar regions.

    Most climate models predict that low cloud cover will decrease as the planet warms, but it has been difficult to say for sure because scientists haven’t had enough information to evaluate the models. That’s beginning to change. Using data from two NASA satellites, CloudSat and CALIPSO, Cesana plans to evaluate how two main types of low clouds — shallow cumulus and stratocumulus — are behaving today, and use this information to estimate how they’ll evolve in the future.

    Shallow cumulus clouds tend to be small, cottony clouds that often have a flat base. Stratocumulus clouds form more of a blanket over the sky. Both types of clouds have different impacts on the climate and could respond differently to climate change. However, their behaviors have been hard to sort out because they have been difficult to monitor from space on a global scale. Since they’re so low in the sky, traditional satellites often can’t see them because they are masked by overlapping higher clouds. In addition, older satellites couldn’t tell apart the different types of clouds accurately. “Now this has become possible because the particular satellites I’m using are able to observe a whole transect, a whole profile of atmosphere from the top to the base,” said Cesana. “You can see what’s happening in the atmosphere at every level with a better vertical and horizontal resolution than previous satellites. We are now able to tell the stratocumulus and shallow cumulus clouds apart, and we can use this to evaluate their behavior in the models.”

    How to analyze a cloud in the sky

    The project will also study stratocumulus clouds, which tend to form a thin blanket over the sky. Photo: Falcon747/Wikimedia Commons

    Cesana will use the satellite data to study how the low clouds are responding to surface temperature and the stability of the lower troposphere, the two main factors that control low cloud formation. Understanding this relationship in the present day will make it possible to test how well the models simulate present-day low cloud behavior. It will also make the future of low clouds much clearer, assuming that the models simulate the correct change of temperature and stability.

    “If you know how the surface temperature and stability will evolve in the future, then you can tell how the low clouds are going to evolve in the future,” Cesana explained.

    At the end of the three-year project, he plans to compare his findings to simulations from two of the most widely used climate model experiments (CMIP5 and CMIP6). If the models match his data, then they’re doing a good job of modeling the clouds’ response to global warming. If not, it would mean the models are probably not accurately representing the relationships between surface temperature, stability, and low cloud behavior, and would need to be refined.

    Cesana’s project recently received funding through NOAA’s Modeling, Analysis, Predictions, and Projections program. He expects to have some preliminary results next year, and hopes that the work will eventually help to reduce uncertainty around low cloud feedbacks in climate models, so that projections for future warming will be more accurate.

    Every degree or even half of a degree of global warming can have widespread and devastating impacts, said Cesana, “so it’s very important to be able to narrow this down.”

    On the occasion of the 58th International Art Exhibition of the Venice Biennale, the great artist Jan Fabre returns to the lagoon with a special project of public art, a unique open-air installation. Installed in the Garden of Palazzo Balbi Valier and visible from the Grand Canal, The Man Who Measures the Clouds (Monument to the Measure of the Immeasurable) appears as a towering golden man rising to a height of nine metres.

    The project stems from the collaboration of Angelos (Antwerp, BE), EdM Productions and the Fondation Linda et Guy Pieters (Saint-Tropez, FR) and is curated by Joanna De Vos. It will be unveiled to the public at 5 pm on Monday 6 May and remain in place until the end of the 2019 Art Biennale, on Sunday 24 November.

    It is over the tenth time that Jan Fabre contributes as an active part in the great Venetian jamboree, where he first participated in 1984 at the age of twenty-six, as Belgium’s representative in the Giardini. Since then, Fabre has been present both as one of the officially selected artists and in relation to collateral events.

    The Man Who Measures the Clouds (Monument to the Measure of the Immeasurable) is a new and unique monumental work finished in gold leaf. It’s especially conceived for Venice, making a deep connection with this city stretching back decades. Protruding above the arch leading into the Garden of Palazzo Balbi Valier from the Grand Canal, this towering golden man reflects not only the drift of the artist and mankind, but also the historic significance and values of this mythical floating city.

    The sculpture’s title refers to the story of the legendary Birdman of Alcatraz, Robert Stroud, who at the time of his release from prison had declared that from that moment on he was ‘going to measure the clouds’, and is an invitation for us to reflect on the artist’s role in society. The work can be interpreted as a “metaphor for the artist who tries to capture the impossible in his work”, to quote Fabre’s own words, and might take its inspiration from the philosopher Protagoras’ assertion: ‘Man is the measure of all things: of the things that are, that they are, of the things that are not, that they are not.’ For the Greeks, man was the unit of measurement of the mutual relationship between objects and, in the same way, Fabre’s man stands as the measure of all things, in tribute to the grandeur of the human imagination.

    From the Greeks until today we love monumentality: the bigger, the more visible and the more powerful. The scale and dimensions of Fabre’s sculpture, together with its open-air installation in Venice, has a profound impact upon its meaning and the way it’s experienced. Does Jan Fabre use the enormous height of this sculpture to make the extent of human endeavour physically visible? Man always wants to measure himself and he loves to excel, it is impossible to overlook these facts in a historical city such as Venice.

    We see a man dressed in contemporary clothing standing on a stepladder with his arms stretched out towards the sky, holding in his hands a ruler with which he is trying to measure objects in the sky.
    The body seems identical to Fabre’s own, but in fact the countenance is modelled after his later brother, Emiel Fabre, who died at a very young age. Jan Fabre and his brother were the spitting images of each other. The longitudinal thrust of the body contrasts with the marked horizontality of the ruler he is holding, producing a climax where a temporary reconciliation takes place between horizontal tension and verticality. The fragile balance of the composition echoes the perfection to which humanity aspires, to the point of making itself the unit of measurement of the whole of creation, of reaching for the sky with its monumental works of art and magnificent buildings that are tangible testimonies to its desire to attain ever greater heights.

    The silicon bronze sculpture is finished with a coating of gold leaf, turning it into a sort of contemporary idol/icon. The monumental size and its golden glow restore magnificence to the human enterprise.
    The use of gold in the setting of Venice also recalls a multitude of connections with the history of the city and the people who lived in it and made it a commercial power for centuries. It was in Venice, in fact,
    that the first gold coin was struck in 1284, the so-called ducat was to remain the benchmark for all the currencies of Europe for 600 years. Today, it is in Venice that the ancient craft of goldbeating has survived, at the only studio in Europe that is still capable of utilizing the original techniques of the 18th century.

    So who is this measurer of the unknown dreaming of being able to grasp the size of the unmeasurable? Jan Fabre leaves viewers in doubt, with a ‘creative thought’ that prompts them to lift their eyes and gaze at the vastness of the sky above Venice and of the prospects for humanity itself. Jan Fabre gives us a monument to the measure of the immeasurable. He challenges the spectator
    to rethink the meaning of scale.

    The project will be accompanied by a publication with an essay by curator Joanna De Vos, in a limited edition of 300 copies, 200 of them numbered and signed by Jan Fabre and Joanna De Vos;
    graphic design by Aline Billiet.

    University of Leeds provides funding as a founding partner of The Conversation UK.


    This is an article from Curious Kids, a series for children of all ages. The Conversation is asking young people to send in questions they’d like an expert to answer. All questions are welcome. Skip to the bottom to see how to enter.

    How do the clouds stay up in the sky? – Samson, age four, London, UK.

    Thanks for the question, Samson. Believe it or not, I once weighed a cloud and not many people can say they have done that! My scientist friends and I flew up into the sky in a giant airship, and went all the way through a fluffy, white cloud. Actually, it was very wet up there, because clouds are made up of billions of tiny water droplets.

    As we flew through the cloud, we used lasers and other special scientific devices to measure how big the cloud was, and count how many tiny droplets of water were in it. Then, we did some maths and found that this cloud – which was actually pretty small, for a cloud – weighed four tonnes. That’s the same as two elephants! So, you’re right to wonder how such a heavy thing can stay up in the sky.

    There are three pieces to this puzzle, and the first one is gravity. Like everything on this planet, the tiny droplets that make up a cloud are drawn towards the Earth by gravity. But these droplets are so small that it’s hard for them to push past all the air beneath them. This means that they don’t fall very fast at all – in fact, only about one centimetre per second. And any wind blowing upwards can carry the droplets back up.

    To fit the second piece of the puzzle, we’ll need to learn some proper chemistry; not too much, though, just enough for our story. Let me introduce the periodic table: a map of all the elements that we humans know about. Elements are the building blocks of all things – just like the smallest pieces of Lego, which you use to build bigger and more complex objects.

    The periodic table is organised so that the lightest element of each row is always on the left. Hydrogen is the lightest of all elements, so you’ll find it at the top left. As you move along each row from left to right, the elements get heavier and heavier.

    Dry air is mostly made up of two gases, nitrogen and oxygen, plus a little bit of argon and tiny amounts of other gases. For now, we can just focus on nitrogen and oxygen. As you can see on the periodic table, the weight of a single nitrogen atom is 14, while oxygen weighs almost 16.

    But neither nitrogen nor oxygen atoms like to be alone, so they almost always go in pairs – two atoms in a molecule, like two peas in a pod. Because of this, a nitrogen molecule usually weighs 28, and an oxygen molecule weighs 32.

    As soon as we add water (H₂O) to the air, things get interesting. A water molecule is made up of two hydrogen atoms and one oxygen atom. Remember how hydrogen is the lightest element? Well, a single water molecule weighs just 18. So it’s actually lighter than a molecule of nitrogen or oxygen. That’s why moist air is lighter than dry air.

    The next piece of the puzzle is temperature. As a rule, warm air rises up, while cold air sinks down. When water in the air is warmer, it’s more likely to be a gas. When it’s cooler, it prefers to take a liquid form, such as cloud droplets, rain, hail or snow.

    How to analyze a cloud in the sky

    As warm, moist air rises, it gets cooler and cooler. And as it cools, more tiny water droplets form. You might expect the water droplets just to fall down as rain, but instead, something fun happens. You know how sweat cools our skin when it dries and changes from liquid into gas? Well, when gas turns into liquid, the exact opposite happens: it actually gives off heat.

    This means that the cloud droplets are now surrounded by a tiny blanket of warm air. And what does warm air do? It rises! Not very far, though, because the air will cool again as it goes up.

    Now our puzzle is complete: clouds are made up of tiny droplets of water, which are hardly affected by gravity, embedded in moist air, which is lighter than dry air. And they’re surrounded by tiny warm blankets of air, which lift them up towards the sky. That’s how clouds weighing billions of tonnes can stay afloat up in the sky.

    Hello, curious kids! Have you got a question you’d like an expert to answer? Ask an adult to send your question to us. You can:

    * Email your question to [email protected]
    * Tell us on Twitter by tagging @ConversationUK with the hashtag #curiouskids, or
    * Message us on Facebook.

    How to analyze a cloud in the sky

    Please tell us your name, age and which town or city you live in. You can send an audio recording of your question too, if you want. Send as many questions as you like! We won’t be able to answer every question, but we will do our best.

    This article has been updated to reflect the effects of air resistance and gravity on cloud droplets more accurately.

    Salesforce Marketing Cloud (formerly, ExactTarget) is a provider of digital marketing automation and analytics software and services.


    Alteryx is a powerful and flexible end-to-end analytics platform for creating data partnerships between IT, analytic teams, and the lines of business.

    Analyze Your Salesforce Marketing Cloud with Alteryx

    The best way to perform an in-depth analysis of Salesforce Marketing Cloud data with Alteryx is to load Salesforce Marketing Cloud data to a database or cloud data warehouse, and then connect Alteryx to this database and analyze data. Skyvia can easily load Salesforce Marketing Cloud data (including Accounts, Opportunities, Contacts, Data Extensions, etc.) to a database or a cloud data warehouse of your choice.

    Source Skyvia Data Warehouse BI Tool

    Select Database or Data Warehouse You Like

    • Oracle
    • MySQL
    • PostgreSQL
    • SQL Server
    • SQL Azure
    • Amazon RDS
    • Amazon Aurora
    • MariaDB
    • Google Cloud SQL MySQL
    • Google Cloud SQL PostgreSQL
    • Heroku Postgres
    • Azure MySQL
    • Azure PostgreSQL
    • Google BigQuery
    • Amazon Redshift
    • Snowflake
    • Azure Synapse Analytics

    Select How You Want to Load Data

    ELT (Replication)

    ELT process supposes simple copying cloud data to a data warehouse or a database as-is, leaving all the transformation tasks for the database server. This is often uses, for example, when loading data to cloud data warehouses with affordable and nearly unlimited computing power for transformations. In Skyvia, this task is solved with easy-to-configure Replication packages.

    ETL (Import)

    ETL process supposes that data structure in source and target is different, and data must be transformed before loading it into target database. For example, you may want to create a schema for OLAP or simply have target tables for data already created. In Skyvia, this is task solved with Import packages, having powerful mapping and transformation capabilities.

    Replication Features

    Simple No-coding Setup

    All you need to do is to specify parameters for connecting to Salesforce Marketing Cloud and data warehouse and select which data to replicate.

    Keep Data Up-to-Date

    Skyvia’s Replication Tool will painlessly ensure you always have the most current data from your cloud applications in your data warehouse.

    Automatic Schema Creation

    You don’t need to prepare the database — Skyvia creates the tables, corresponding to the source objects, in the data warehouse automatically.

    Import Features

    Powerful Data Transformations

    Skyvia offers powerful mapping features for data transformations. You can perform data splitting, use complex expressions and formulas, lookups, etc.

    Import of New and Updated Data

    You can import only new and updated records, and thus, keep your database for analysis always up-to-date.

    Preserve Data Relations

    With Skyvia all the relations between the imported Salesforce Marketing Cloud objects will be preserved. You need just to specify them in mapping.

    Integrate Salesforce Marketing Cloud and Alteryx with minimal effort and in only a few clicks!

    Turn an old CD into a spectroscope to analyze light—you may be surprised by what you see. Try pointing your CD spectroscope at the fluorescent light in your room, sunlit clouds in the sky, even your friend’s colored shirt to reveal the wavelengths of light that mix together to create the color you see!

    Video Demonstration

    How to analyze a cloud in the sky

    How to analyze a cloud in the sky

    How to analyze a cloud in the sky

    How to analyze a cloud in the sky

    Tools and Materials

    How to analyze a cloud in the sky

    • A compact disc (CD)
    • A cardboard tube that’s at least 12 inches long (approximately 30 centimeters) and 3 to 4 inches (7.5 to 10 centimeters) in diameter
    • Two covers for the cardboard tube—we suggest two flat pieces of cardboard large enough to cover each end of the tube, or you can also use the plastic covers that come with a cardboard packing tube.
    • Razor knife such as an X-ACTO knife
    • Tape
    • Access to fluorescent light
    • Saw
    • Cutting guide (scaled for a 3-inch tube)—PDF included
    • Access to a printer


    To help you build your spectroscope, we’ve created a cutting guide (PDF included). Print the cutting guide and wrap it around your tube. We’ve scaled the guide for a standard 3-in packing tube. If needed, you can scale the guide to ensure it wraps around your tube without a gap or overlap (see below).
    How to analyze a cloud in the sky

    To Do and Notice

    Hold the tube upright and point the top slit at a fluorescent light.

    Press your eye to the viewing hole.

    On the CD, look for a clear, solid line of light broken up into colored bands: this is the spectrum of light reflected from fluorescent light onto the CD.

    Adjust the angle at which you look through the viewing hole at the CD to find the best view of the light spectrum.

    Notice that the fluorescent light produces bright lines. The bright lines are the spectrum of mercury gas inside the tube. An incandescent light, by comparison, makes a continuous spectrum.

    What’s Going On?

    All light is made up of waves of electromagnetic radiation. A spectroscope spreads each different wavelength to a different position within a spectrum of light.

    Music is digitally recorded as circular tracks of ones and zeros on the mirrored surface of a CD. These circular tracks are so close together that they can act as a diffraction grating for light.

    When the light enters the tube, it is spread into a spectrum perpendicular to the CD tracks. This is why the slit and the viewing hole are located at right angles.

    Each color bends at a particular angle. For you to see the spectrum, the light must diffract off the CD and reflect into your eye. Adjusting the tilt of the CD allows you to properly bounce the spectrum into your eye.

    Going Further

    Examine the spectra produced by other light sources, such as light-emitting diodes (LEDs), sodium-vapor streetlights, and neon tubes.

    When you look at an incandescent light and a fluorescent light by eye they might appear to be the same shade of white, yet looking at them with a spectroscope reveals that they are composed of two totally different spectra.

    In 1788, Comte de Buffon said that he was sure we would never know what the sun was made of. You can look through your spectroscope and prove him wrong. Be careful not to look directly at the sun, but you can use the spectroscope to look at sunlight reflected off white clouds, white walls, or white paper to see the spectrum of the sun. If you make an excellent top slit on a long tube (24 in or 60 cm) you may even see thin dark lines in the solar spectrum; these are called Fraunhofer lines and reveal what the sun is made of.

    In the 1860s, William Huggins discovered what the stars were made of by viewing them through a spectroscope.

    Your CD spectroscope connects you to a long history of discovery!

    This Science Snack is part of a collection that showcases LGBT artists, scientists, inventors and thinkers whose work aids or expands our understanding of the phenomena explored in each Snack.

    How to analyze a cloud in the sky

    Source: Jörg Meyer for Columbia College Today. Used with permission.

    Dr. Rebecca Oppenheimer (pictured above) is a comparative exoplanetary scientist; she studies planets that are outside of our solar system. She has been a leader for many projects relating to exoplanet study, including the Advanced Electro Optical System (AEOS) Telescope in Maui, Project 1640 at the Palomar Observatory, and a starlight suppression system for the International Gemini Observatory Planet Imager project (GPI), which was conducted in her own lab. Dr. Oppenheimer’s optics laboratory in the Rose Center for Earth and Space is the birthplace of various new astronomy-related devices that have led to the ability to directly see and take spectra of nearby solar systems. With the CD Spectroscope Science Snack, you can see for yourself different colors and wavelengths of light all around you.

    I Wandered Lonely As A Cloud is interpreted in many different and contrasting ways. When first reading this poem, little meaning was conveyed to me; it was just a poem. He seems simply to be describing a whimsical scene of solitude in nature. He mentions several aspects of nature during his walk along the lake, describing clouds, the landscape’s profile, most importantly the daffodils, and the stars. This focus on nature lead me to believe he was writing to express its beauty and his connection with it; admiring the daffodils, as they sway gaily.

    When discovering the walk was taken with his sister, who had been excluded from the poem, I thought he might be describing a moment of experiencing the Sublime [See Sublime: Romanticism]. The Sublime, as one of the key concepts of Romanticism that describes a euphoric feeling when alone in nature, ties in well with Wordsworth’s connection with nature and I thought she might have been excluded to prove this experience. However, his emotions are not evoked by the daffodils as they would be in a moment of the sublime. His feelings are more subdued than ideas of Sublime enlightenment, and the scene is not the most vast natural landscape.

    His focus on the small flowers dancing by the lake, detached from the scene as a whole, creates a personal perspective. He speaks of them as a whole, a host, not seeing them as individual plants but as a synchronized crowd, still separate from other aspects of nature, and separate from himself. He seems to not share their joy, but observe in reserved thought. It isn’t until later, when apart from the natural scene depicted, that he appreciates and shares the moment with them and “dances with the daffodils” rather than observing from above, as a lonely cloud. I could then interpret it as a symbol of his loneliness. He, at first wanders alone, a silent, reserved, envious onlooker. But later sees himself among them, dancing as part of the synchronized group and no longer excluded from their delightful fluttering. This can be applied to his social life, especially in the secluded area in which he chose to live. He spent much of his time with his sister, implying that perhaps she is one of his only friends. The death of his parents may have caused him to become introverted at a young age and never quite feel a part of a group or society; never in sync with the daffodils.

    Although, to me, this perspective of the poem summons the most meaning, a few of the ideas contradict those in other poems of his. His admiration for the daffodils, if they are a metaphor for the people of society, contradicts his aversion to society’s traditions and social laws. In other poems his seems distressed at the direction in which society is moving – away from the ideals of romanticism – and views them as blind to the important things. If he is using the daffodils to represent the society that he is indifferent to, why does he vie them with such awe and wonder? Does his loneliness stem from the controversial views he holds, causing him to be cut off from others? Does he wish society to be as beautiful and natural as the daffodils in the poem? Or do the daffodils represent an idealist society of which he wishes to be a part of, but is not as there is no such society?

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    One thought on “ I Wandered Lonely As A Cloud ”

    I am very disappointed in your lack of daffodil cartoons. you are better than this….
    I enjoyed reading about your interpretation of the poem, particularly the theory that the daffodils were themselves a metaphor for Wordsworth’s life and social status. I also liked how you explained that his introverted manner may have stemmed from the early loss of his parents. This idea could have perhaps been expanded on and you could have talked about some other reasons for his subdued social behavior. Your points about the role of the sublime in the poem were interesting but I felt as if you needed to explain yourself more clearly. You kept referring to the sublime in the context of the poem, however, a short explanation about what the sublime actually is could have helped to strengthen your point, especially to those who have not read your earlier blog posts.

    Juniper ATP Cloud uses a pipeline approach to analyzing and detecting malware. If an analysis reveals that the file is absolutely malware, it is not necessary to continue the pipeline to further examine the malware. See Figure 1.

    Figure 1: Example Juniper ATP Cloud Pipeline Approach for Analyzing Malware How to analyze a cloud in the sky

    Each analysis technique creates a verdict number, which is combined to create a final verdict number between 1 and 10. A verdict number is a score or threat level. The higher the number, the higher the malware threat. The SRX Series device compares this verdict number to the policy settings and either permits or denies the session. If the session is denied, a reset packet is sent to the client and the packets are dropped from the server.

    Cache Lookup

    When a file is analyzed, a file hash is generated, and the results of the analysis are stored in a database. When a file is uploaded to the Juniper ATP Cloud cloud, the first step is to check whether this file has been looked at before. If it has, the stored verdict is returned to the SRX Series device and there is no need to re-analyze the file. In addition to files scanned by Juniper ATP Cloud, information about common malware files is also stored to provide faster response.

    Cache lookup is performed in real time. All other techniques are done offline. This means that if the cache lookup does not return a verdict, the file is sent to the client system while the Juniper ATP Cloud cloud continues to examine the file using the remaining pipeline techniques. If a later analysis returns a malware verdict, then the file and host are flagged.

    Antivirus Scan

    The advantage of antivirus software is its protection against a large number of potential threats, such as viruses, trojans, worms, spyware, and rootkits. The disadvantage of antivirus software is that it is always behind the malware. The virus comes first and the patch to the virus comes second. Antivirus is better at defending familiar threats and known malware than zero-day threats.

    Juniper ATP Cloud utilizes multiple antivirus software packages, not just one, to analyze a file. The results are then fed into the machine learning algorithm to overcome false positives and false negatives.

    Static Analysis

    Static analysis examines files without actually running them. Basic static analysis is straightforward and fast, typically around 30 seconds. The following are examples of areas static analysis inspects:

    Metadata information—Name of the file, the vendor or creator of this file, and the original data the file was compiled on.

    Categories of instructions used—Is the file modifying the Windows registry? Is it touching disk I/O APIs?.

    File entropy—How random is the file? A common technique for malware is to encrypt portions of the code and then decrypt it during runtime. A lot of encryption is a strong indication a this file is malware.

    The output of the static analysis is fed into the machine learning algorithm to improve the verdict accuracy.

    Dynamic Analysis

    The majority of the time spent inspecting a file is in dynamic analysis. With dynamic analysis, often called sandboxing, a file is studied as it is executed in a secure environment. During this analysis, an operating system environment is set up, typically in a virtual machine, and tools are started to monitor all activity. The file is uploaded to this environment and is allowed to run for several minutes. Once the allotted time has passed, the record of activity is downloaded and passed to the machine learning algorithm to generate a verdict.

    Sophisticated malware can detect a sandbox environment due to its lack of human interaction, such as mouse movement. Juniper ATP Cloud uses a number of deception techniques to trick the malware into determining this is a real user environment. For example, Juniper ATP Cloud can:

    Generate a realistic pattern of user interaction such as mouse movement, simulating keystrokes, and installing and launching common software packages.

    Create fake high-value targets in the client, such as stored credentials, user files, and a realistic network with Internet access.

    Create vulnerable areas in the operating system.

    Deception techniques by themselves greatly boost the detection rate while reducing false positives. They also boosts the detection rate of the sandbox the file is running in because they get the malware to perform more activity. The more the file runs the more data is obtained to detect whether it is malware.

    Machine Learning Algorithm

    Juniper ATP Cloud uses its own proprietary implementation of machine learning to assist in analysis. Machine learning recognizes patterns and correlates information for improved file analysis. The machine learning algorithm is programmed with features from thousands of malware samples and thousands of goodware samples. It learns what malware looks like, and is regularly re-programmed to get smarter as threats evolve.

    Threat Levels

    Juniper ATP Cloud assigns a number between 0-10 to indicate the threat level of files scanned for malware and the threat level for infected hosts. See Table 1.

    A guide to hinge connections and how to model them in Structural 3D

    What is a Hinge Joint?

    Firstly, what is a hinge joint? A hinge connection allows two members to rotate around their connection. At the hinge, both members are able to rotate freely with no restraint. Take the following diagram:

    You can see how the second member is free to rotate under an applied load. The member is not transferring any bending moment to the other member. This is proven by the fact that there is 0 bending moment at the connecting node, meaning that there is no restraint against bending moment.

    Understanding a Hinge Connection

    The best way to fully comprehend how connections work is to understand how the nodes are connected to the member ends. If it has a fixed degree of freedom, then the member is welded to the node – where the node goes, the member goes! Take the following two members:

    How to analyze a cloud in the sky

    We can see they are joined by a common node. Now let’s separate the members to take a closer look:

    How to analyze a cloud in the sky

    On the left, we have Member 1, fixed to the node with a restraint code of FFF-FFF. On the right, we have Member 2, which for this example has a hole cut out of it that allows the node to slide along the X and rotate about the Z. This is denoted by RFF-FFR. I have chosen this example because it is easy to understand and visualize the movement along the X-axis. This is an example of a hinge joint that can translate in the X. If you want to restrict the movement along the local x-axis, simply model the following connection:

    How to analyze a cloud in the sky

    How to Model the Hinge Joint

    Once we understand our end fixities, it’s time to model this in the software. Take a simple connection between two members:

    How to analyze a cloud in the sky

    To change this connection (node 2 in the diagram) to a hinge joint, we just need to change one of the member fixities to being FFF-FFR (as seen below). We can see Member 1’s end is denoted by ‘FFFFFR’ in the left input menu. In doing this, we should see a little ‘dash’ added to the diagram, denoting that the member is no longer a fixed connection:

    How to analyze a cloud in the sky

    After we analyze the structure, we can check to see whether there is any bending moment force at the connection. Since the bending force is not being transferred between members, there should be 0 bending moment at the node where a hinge exists:

    There are many different types of clouds, each with a unique shape and location in the sky.

    Clouds are given different names based on their shape and their height in the sky. Some clouds are puffy like cotton while others are grey and uniform. Some clouds are near the ground, while others are near the top of the troposphere. The diagram on the right shows where different types of clouds are located in the sky.

    How Are Clouds Classified?

    Most clouds can be divided into groups (high/middle/low) based on the height of the cloud’s base above the Earth’s surface. Other clouds are grouped not by their height, but by their unique characteristics, such as forming alongside mountains (Lenticular clouds) or forming beneath existing clouds (Mammatus clouds).

    The table below provides information about cloud groups and any cloud types associated with them. Click on the cloud images in the table to learn more about each cloud type.

    Cloud Group and Height *

    Cloud Types

    High Clouds

    5 – 13 km (16,000 – 43,000 ft)

    Noctilucent clouds are the highest clouds in the sky, however they are not associated with weather like the rest of the clouds in this table

    Middle Clouds

    2 – 7 km (7,000 – 23,000 ft)

    Low Clouds

    Surface – 2 km (surface – 7,000 ft)

    Clouds with Vertical Growth

    Surface – 13 km (surface – 43,000 ft)

    Clouds that grow up instead of spreading out across the sky.

    Unusual Clouds

    Clouds that form in unique ways and are not grouped by height.


    5 – 13 km (16,000 – 43, 000 ft)

    * The cloud heights provided in this table are for the mid-latitudes. Cloud heights are different at the tropics and in the polar regions. In addition, a few other cloud types are found in higher layers of the atmosphere. Polar stratospheric clouds are located in a layer of the atmosphere called the stratosphere. Polar mesospheric clouds, which are also called noctilucent clouds, are located in the atmospheric layer called the mesosphere.

    © 2019 UCAR with portions adapted from Windows to the Universe (© 2009 NESTA)

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    Future Generation Computer Systems



    Modern soft X-ray observatories can yield unique insights into time domain astrophysics, and a huge amount of information is stored – and largely unexploited – in data archives. Like a treasure-hunt, the EXTraS project harvested the hitherto unexplored temporal domain information buried in the serendipitous data collected by the European Photon Imaging Camera instrument onboard the ESA XMM-Newton, in 16 years of observations. All results have been released to the scientific community, together with new software analysis tools. This paper presents the architecture of the EXTraS science gateway, that has the goal to provide the software through a web based portal using the EGI Federated Cloud infrastructure. The main focus is on the light software architecture of the portal and on the technological insights for an effective use of the EGI ecosystem.


    We present a science gateway for astrophysical research based on PortalTS.

    It provides the main analysis tools made publicly available in the EXTraS project.

    It allows to analyze all the observations of the XMM-Newton Science Archive.

    We present technical insights for an effective exploitation of EGI Federated Cloud services.

    Wayfinder navigators always look for signs of weather at sunrise and sunset. This is when they try to predict the weather for the next 12 hours.

    One of the easiest ways to predict weather is to look at the clouds. There are many different types of clouds in the troposphere (where all weather forms). Different clouds mean different types of weather.

    Cloud names that describe the shapes of clouds are:

    • cirrus – meaning curl (as in a lock of hair) or fringe
    • cumulus – meaning heap or pile
    • stratus – meaning spread over an area or layer.

    Nimbus means rain-bearing, and alto means high. The following are some of the more common clouds used to predict weather in three categories – high-level, mid-level and low-level clouds.

    High-level clouds

    The bases of these clouds form at about 6200 metres above sea level. They are usually composed of ice crystals.

    • Cirrus clouds – thin, wispy clouds strewn across the sky in high winds. A few cirrus clouds may indicate fair weather, but increasing cover indicates a change of weather (an approaching warm front) will occur within 24 hours. These are the most abundant of all high-level clouds.
    • Cirrocumulus – like ripples or fish scales (sometimes called a mackerel sky). When cirrus clouds turn into cirrocumulus, a storm may come – in tropical regions, that could be a hurricane.
    • Cirrostratus – like thin sheets that spread across the sky and give the sky a pale, whitish, translucent appearance. They often appear 12–24 hours before a rainstorm or snowstorm.

    Mid-level clouds

    The bases of these clouds form at about 2000–6200 m above sea level. They are mostly made of water droplets but can contain ice crystals. The clouds are often seen as bluish-grey sheets that cover most, if not all, of the sky. They can obscure the Sun.

    • Altocumulus – composed of water droplets and appear as layers of grey, puffy, round, small clouds. Altocumulus clouds on a warm, humid morning may mean thunderstorms late in the afternoon.

    Low-level clouds

    The bases of these clouds form at altitudes below 2000 m. They are mostly made of drops of water.

    • Cumulus – known as fair-weather clouds because they usually indicate fair, dry conditions. If there is precipitation, it is light. The clouds have a flattish base with rounded stacks or puffs on top. When the puffs look like cauliflower heads they’re called cumulus congestus or towering cumulus. They can get very high.
    • Cumulonimbus clouds – thunder clouds that have built up from cumulus clouds. Their bases are often quite dark. These clouds can forecast some of the most extreme weather, including heavy rain, hail, snow, thunderstorms, tornadoes and hurricanes.
    • Stratus – dull greyish clouds that stretch across and block the sky. They look like fog in the sky. Stratus cover is also called overcast. If their bases reach the ground, they become fog. They can produce drizzle or fine snow.
    • Stratocumulus – low, puffy and grey, forming rows in the sky. They indicate dry weather if the temperature differences between night and day are slight. Precipitation is rare, but they can turn into nimbostratus clouds.
    • Nimbostratus – dark grey, wet-looking cloudy layer so thick that it completely blocks out the Sun. They often produce precipitation in the form of rain and/or snow. Precipitation can be long lasting.

    Cloud roads

    Wayfinder navigators use clouds to work out where the wind is coming from or if it changes direction (so they can trim their sails accordingly). For example, they might look for cloud roads – puffs of cloud that come up from the far end of the horizon to form a ‘road’ in the sky. Like smoke from a haystack, cloud roads follow the wind. A cloud road indicates the wind is coming from the horizon. If the road is straight, the wind is steady – but if you see the road curve, it means that the wind direction will change. The way the road curves will tell you the new direction. Meteorologists call this kind of phenomenon ‘cloud streets’.

    Examples of navigator weather talk

    Navigators realise you can’t predict the weather from a single snapshot – that is, by noting how the sky looks at one moment in time. Instead, you have to observe changes over time.

    Here are some examples of statements from navigator Nainoa Thompson concerning navigation and the weather (recorded by Sam Low during Hōkūle’a’s voyage from Tahiti to Hawai’i in February 2000):

    • “The sky where the Sun is rising is clear – there are no smoky clouds caused by strong winds stirring salt into the atmosphere – so the winds will be relatively light today.”
    • “There’s a change from seeing squalls off the starboard side yesterday to a view of high towering cloud masses but no active squalls. The wind feels stronger than the day before, and I can see wavelets on the surface of the ocean. The wind is coming from the normal direction of SE trade winds. There are low-level cumulus clouds ahead. No indications of squalls – approaching an area of clean-flowing wind from SE, which will be steady. Predict that, in the next 12 hours, the wind will remain steady from the SE at a fairly constant speed, maybe 10 knots, so we will be able to sail north today.”

    Related content

    The Connected article Sun, wind or rain? covers weather prediction.

    Activity ideas

    Clouds and the weather observes cloud types and how they help predict the weather.

    Precipitation and cloud formation uses a slide show to help explain cloud and precipitation processes.

    Useful links

    Read the story of the Hōkūle’a and the beginnings of the wayfinding voyages of rediscovery. Explore the site for voyage tracking maps, learning journeys, videos, teaching activities and more related to the art and science of Polynesian voyaging.

    Nephology, the study of clouds has always been a daydreamer’s science. It was founded by a young student who preferred to stare out the window rather than pay attention in class. This TED-Ed video explains how Luke Howard named and classified clouds.

    How to analyze a cloud in the skyIn this world of cloud, one of the biggest features is the ability to scale. There are different ways to accomplish scaling, which is a transformation that enlarges or diminishes. One is vertical scaling and the other is horizontal scaling.

    What is the difference between the two? If you look at just the definitions of vertical and horizontal you might see the following:

    • Vertical: something that is standing directly upright at a right angle to the flat ground
    • Horizontal: something that is parallel to the horizon (the area where the sky seems to meet the earth)

    If you are a visual kind of person you may be able to see this. Let’s add some technology to this and see what we get.

    Vertical scaling can essentially resize your server with no change to your code. It is the ability to increase the capacity of existing hardware or software by adding resources. Vertical scaling is limited by the fact that you can only get as big as the size of the server.

    Horizontal scaling affords the ability to scale wider to deal with traffic. It is the ability to connect multiple hardware or software entities, such as servers, so that they work as a single logical unit. This kind of scale cannot be implemented at a moment’s notice.

    So, having said all that, I always like to provide an example that you might be able to visually imagine.

    Imagine, if you will, an apartment building that has many rooms and floors where people move in and out all the time. In this apartment building, 200 spaces are available but not all are taken at one time. So, in a sense, the apartment scales vertically as more people come and there are rooms to accommodate them. As long as the 200-space capacity is not exceeded, life is good.

    This could even apply to a restaurant. You have seen the signs that tell you how many people could be held in the establishment. As more patrons come in more tables may be set up and more chairs added (scaling vertically). However when capacity is reached no more patrons would be able to fit. You can only be as big as the building and patio of the restaurant. This is much like in your cloud environment, where you could add more hardware to the existing machine (RAM and hard drive space) but you are limited to capacity of your actual machine.

    On the horizontal scaling side, imagine a two lane expressway. The expressway is good to handle the 2,000 or so vehicles that travel the expressway. As commerce begins to expand, more buildings are constructed and more homes are built. As a result the expressway that once handled 2,000 or so vehicles is now having an increase to 8,000 vehicles. This makes a major traffic jam during rush hour. To alleviate this problem of traffic jams and an increase in accidents, the expressway can be scaled horizontally by constructing more lanes and quite possibly adding an overpass. In this example the construction will take some time. Much like scaling your cloud horizontally, you add additional machines to your environment (scaling wider). This requires planning and making sure you have resources available as well as making sure your architecture can handle the scalability.

    I think this could be a simple way to explain scalability to a customer if they wanted to know the difference between vertical and horizontal scaling in the cloud. What are your thoughts? How have you described scalability? Leave a comment below and let me know.

    In Stanza 1, the host of golden daffodils are dancing in the breeze. In Stanza 4, the waves of the bay were dancing according to the poets creative eye. When the author notices that the daffodils and the waves were “Dancing” it gives off a joyful mood, and shows how nature was happy in his poem, and set a postitive tone


    Dancing for the daffodils could be them swaying in the breeze, in a rocking motion. The waves come back and forth which can be though of as dancing in a creative way.

    Cirrostratus clouds are thin, sheetlike high clouds that often cover the entire sky. They are so thin that the sun and moon can be seen through them. Cirrostratus clouds usually come 12-24 hours before a rain or snow storm.

    Cirrocumulus clouds appear as small, rounded white puffs that appear in long rows. The small ripples in the cirrocumulus clouds sometime resemble the scales of a fish. Cirrocumulus clouds are usually seen in the winter and indicate fair, but cold weather. In tropical regions, they may indicate an approaching hurricane.

    “Alto” Clouds
    Altostratus clouds are gray or blue-gray mid level clouds composed of ice crystals and water droplets. The clouds usually cover the entire sky. In the thinner areas of the clouds, the sun may be dimly visible as a round disk. Altostratus clouds often form ahead of storms with continuous rain or snow.

    Altocumulus clouds are mid level clouds that are made of water droplets and appear as gray puffy masses. They usually form in groups. If you see altocumulus clouds on a warm, sticky morning, be prepared to see thunderstorms late in the afternoon.

    Stratus Clouds
    Stratus clouds are uniform grayish clouds that often cover the entire sky. They resemble fog that doesn’t reach the ground. Light mist or drizzle sometimes falls out of these clouds.

    Stratocumulus clouds are low, puffy and gray. Most form in rows with blue sky visible in between them. Rain rarely occurs with stratocumulus clouds, however, they can turn into nimbostratus clouds.

    Nimbostratus clouds form a dark gray, wet looking cloudy layer associated with continuously falling rain or snow. They often produce precipitation that is usually light to moderate.

    Cumulus Clouds
    Cumulus clouds are white, puffy clouds that look like pieces of floating cotton. Cumulus clouds are often called “fair-weather clouds”. The base of each cloud is flat and the top of each cloud has rounded towers. When the top of the cumulus clouds resemble the head of a cauliflower, it is called cumulus congestus or towering cumulus. These clouds grow upward and they can develop into giant cumulonimbus clouds, which are thunderstorm clouds.

    Cumulonimbus clouds are thunderstorm clouds. High winds can flatten the top of the cloud into an anvil-like shape. Cumulonimbus clouds are associated with heavy rain, snow, hail, lightning and even tornadoes. The anvil usually points in the direction the storm is moving.

    Special Clouds
    Mammatus clouds are low hanging bulges that droop from cumulonimbus clouds. Mammatus clouds are usually associated with severe weather.

    Lenticular clouds are caused by a wave wind pattern created by the mountains. They look like discs or flying saucers that form near mountains.

    Fog is a cloud on the ground. It is composed of billions of tiny water droplets floating in the air. Fog exists if the atmospheric visibility near the Earth’s surface is reduced to 1 kilometer or less.

    Contrails are condensation trails left behind jet aircrafts. Contrails form when hot humid air from jet exhaust mixes with environmental air of low vapor pressure and low temperature. The mixing is a result of turbulence generated by the engine exhaust.

    Fractus clouds are small, ragged cloud fragments that are usually found under an ambient cloud base. They form or have broken off from a larger cloud, and are generally sheared by strong winds, giving them a jagged, shredded appearance. Fractus have irregular patterns, appearing much like torn pieces of cotton candy. They change constantly, often forming and dissipating rapidly. They do not have clearly defined bases. Sometimes they are persistent and form very near the surface.

    Green Clouds are often associated with severe weather. The green color is not completely understood, but it is thought to have something to do with having a high amount of liquid water drops and hail inside the clouds. In the Great Plains region of the U.S. green clouds are associated with storms likely to produce hail and tornadoes.

    Cloud Activities
    Lesson Plan: Here is a great lesson plan on clouds. In this activity, kids see clouds form when they breath on spoons. When warm, moist breath hits the cool spoon, water vapor condenses and turns into a cloud–or water you can see. Note: This is a PDF file, so you need to have Adobe Acrobat Reader.

    Lesson Plan: Here is a great lesson plan on identifying clouds. In this activity, kids build a cloud finder and identify what clouds they see outside. Note: This is a PDF file, so you need to have Adobe Acrobat Reader.

    Lesson Plan: Here is a great lesson plan focusing on different types of clouds, how they are formed, and what they indicate about the weather. This activity is for grades 3-6. Note: This is a PDF file, so you need to have Adobe Acrobat Reader.

    Cloud Experiment: Here is a great experiment that allows the kids to make a cloud in a bottle.

    Fog Experiment: Here is a great experiment that allows the kids to make fog.

    Pressure Experiment: Here is an experiment that shows how pressure is created in our atmosphere by sucking an egg in a bottle. This is a very cool experiment!

    Make A Barometer Experiment: Here is an experiment that allows the kids to make a barometer.

    Evaporation Experiment: Here is an experiment that shows kids how evaporation takes place.

    Accelerate your game development with Azure PlayFab, build your own cloud game services from scratch, or get support for your indie title with the [email protected] program.

    • Get started with PlayFab
    • Try Azure for free

    Earn the trust of your players

    Azure for game development helps you accelerate game development with Azure PlayFab managed services, build your own game services from scratch, or access developer tools and support with the [email protected] program for indie creators. Reach more players around the world with flexible DevOps tools for every platform and protect your players’ data with enterprise-grade security. Azure for game development is built in partnership with Xbox Game Studios and cloud game developers worldwide.

    1. Bring your creative vision to life faster
    2. Deliver low-latency, reliable gameplay
    3. Scale your game’s multiplayer services
    4. Understand and react to player behavior
    5. Run your game as a service

    How to analyze a cloud in the sky

    Accelerate game production with Azure tools for version control and distributed builds. Collaborate seamlessly with your global team in the cloud or with your existing infrastructure using production pipelines for game creators and studios of all sizes.

    How to analyze a cloud in the sky

    Bring your game title closer to your players and reduce latency for faster and more responsive gaming. Azure has more global datacenter regions (including China) than any other cloud provider. Automate your game server orchestration with Azure PlayFab Multiplayer Servers. Customize and control your own dedicated servers with Azure Virtual Machines. Manage containers with Azure Kubernetes Service for seamless scaling. Simplify your compute tasks with serverless technologies like Azure App Service.

    How to analyze a cloud in the sky

    Bring players together with cross-platform PlayFab Party voice, chat, and translation faster than ever before. PlayFab multiplayer services offer simple yet powerful systems to help your players find each other, compete, communicate, and stay engaged. Grow fearlessly with a set of backend building blocks for your live game.

    How to analyze a cloud in the sky

    Gain real-time insights to understand, grow, and retain your player base. Protect your players with enterprise-level security and GDPR and COPPA compliance. Collect, store, and manage data from your games with Azure PlayFab data and analytics. Or for more customized control, build your own data layer with Azure managed databases.

    How to analyze a cloud in the sky

    Develop successful live games and keep players coming back with PlayFab LiveOps. Build and engage healthy communities by connecting player identities across platforms and enabling user-generated content. Make remote updates to your game store catalog to extend the life of your game and manage your game economy for a better return on investment.

    More benefits of Azure for game development

    Keep your gamers playing

    Safely scale your game experiences with more players and bigger worlds. Azure DDoS Protection mitigates an average of 1,955 attacks per day.

    Increase game development productivity and efficiency

    Move game production to the cloud, hire more distributed developers, and scale up your build farm by creating more virtual machines in just one click.

    Deliver the games your players want

    Use analytics, data, AI, and machine learning to understand your players and update game experiences to keep them coming back.

    Build better games with best-in-class tools

    Connect Perforce Helix Core, Incredibuild, and Unreal Pixel Streaming services, as well as Microsoft Visual Studio, Unreal Engine, Azure PlayFab, and more all in one cloud.

    Handcraft every aspect of your game with Azure

    Get detailed visual guides for integrating backend components to scale and customize game experiences and infrastructure.

    How to analyze a cloud in the sky

    Basic Game Server Hosting on Azure

    A step-by-step guide to setting up a basic Azure backend that will host a game server on either Windows or Linux, using a Minecraft server as an example.

    How to analyze a cloud in the sky

    Synchronous Multiplayer Using Azure Kubernetes Service (AKS)

    Make the move from infrastructure to platform as a service (PaaS). AKS is best for studios with development and DevOps resources looking for a solution that is optimized to fully orchestrate microservices.

    How to analyze a cloud in the sky

    In-Editor Debugging Telemetry Reference Architecture

    As you develop with Visual Studio, improve your game by piping gameplay data from a small sample of players into game engines like Unreal Engine and Unity.

    How to analyze a cloud in the sky

    Synchronous Multiplayer Using Azure Service Fabric

    Get the flexibility to host any variety of PaaS solutions or other container-based solutions without the need for a DevOps team. Let Azure manage hosting for you.

    How to analyze a cloud in the sky

    Multiplayer Serverless Matchmaker

    Learn how to deploy a Multiplayer serverless matchmaker.

    How to analyze a cloud in the sky

    Non-relational Leaderboard Reference Architecture

    Learn how to implement a leaderboard that uses Azure Cache for Redis in tandem with another database.

    Reading a METAR report and understanding weather is an important part of flying. When taking the FAA Part 107 exam for commercial operation of a sUAS, weather and reading METAR / TAF reports make up a large percentage of the test questions, so mastering weather is a must.

    Have any questions about the Part 107? Visit our Drone Community Facebook Group and we’ll do our best to help you!

    How to analyze a cloud in the sky

    Join our Growing Drone Community

    The Aerial Guide Drone Community is a community of drone enthusiasts, professionals, freelancers and entrepreneurs for asking questions, receiving feedback and helping each other level up their skills. All skill levels welcome!

    Like most things on the exam, weather looks like a giant mess when you first look at it – but when you break down the individual pieces of the reports things start to make sense. I’m going to start with a METAR report from the closest airport to me, Cleveland Hopkins Airport on the evening that I’m writing this article.

    Cleveland Hopkins METAR Report

    KCLE 220136Z 31006KT 10SM FEW020 BKN024 OVC049 22/21 A2984 RMK AO2 RAE04 P0000 T02220206

    Right now this might look like a jumble of letters and numbers, but let’s walk through each part of the METAR, line by line.

    METAR Station ID

    K refers to the Continental United States. The three letters after it CLE , refers to the airport. In this case, Cleveland Hopkins Airport.

    METAR Date & Time

    The first two digits 22 refers to the day of the month.

    The next 4 digits 0136 refers to the time when the report was made. The Z refers to ZULU or UTC time.

    METAR Modifier (If any)

    Sometimes the METAR will have a COR or AUTO modifier after the Date & Time. COR means it is a corrected report and AUTO refers to an automated station.

    METAR Wind Speed

    The first three digits 310 is the direction of the wind in degrees.

    The second numbers 06 mean refer to the wind speed in knots.

    Other Wind Speed Terminology

    VRB means that the wind direction can vary, and the gusts are usually light.

    If there is a three digit number V three digit number (Example: 090V180 ), that means that the winds a variable from 90 degrees to 180 degrees. This term comes up when the wind varies over 60 degrees.

    How to analyze a cloud in the sky

    Wind direction, N=0, E=90, S=180, W=270

    METAR Visibility

    This refers to the visibility. The visibility in this example is 10 Statute Miles.

    METAR Present Weather and Obscurations (If any)

    In our METAR report, this isn’t included, but let’s use +SHRA .

    The + means Heavy, SH means Showers and RA means Rain. Look at the legend below for the full list of possibilities.


    (-): Light
    ( ): Moderate [No prefix]
    (+): Heavy


    MI: Shallow
    BC: Patches
    DR: Low Drifting
    BL: Blowing
    SH: Showers
    TS: Thunderstorm
    FZ: Freezing
    PR: Partial


    DZ: Drizzle
    RA: Rain
    SN: Snow
    SG: Snow Grains
    IC: Ice Crystals
    PL: Ice Pellets
    GR: Hail
    GS: Small Hail &/or Snow Pellets
    UP: Unknown Precipitation


    BR: Mist
    FG: Fog
    FU: Smoke
    VA: Volcanic Ash
    DU: Widespread Dust
    SA: Sand
    HZ: Haze
    PY: Spray


    PO: Well-Developed Dust/Sand Whirls
    SQ: Squalls
    FC: Funnel Cloud Tornado Waterspout
    SS: Sandstorm
    DS: Duststorm

    METAR Sky Conditions

    FEW020 BKN024 OVC049

    The next block means the sky conditions. The first three letters FEW are the codes for the amount of coverage in the sky.

    • SKC: Clear
    • CLR: Clear
    • FEW: Few
    • SCT: Scattered
    • BKN: Broken
    • OVC: Overcast

    The next three digits 020 mean the amount of feet (in hundreds) in which the clouds are located.

    In this case, there are Few at 2000 feet, Broken at 2400 feet and Overcast at 4900 feet.

    METAR Temperature & Dew Point

    The first two digits 22 represent the temperature in Celsius.

    The second two digits 21 represent the dewpoint in Celsius.

    To display negative numbers, there will be an M in front of the numbers (Example M04/02 = -04 degress C/ dewpoint: 2).

    METAR Altimeter & Pressure

    The A Represents “Altimeter”. 2984 represents 29.84 inches of mercury for the pressure. This is used so pilots can ensure there altimeter is displaying the right altitude.

    METAR Remarks (Decoding)

    The final section is the remarks section, which is pretty difficult to understand because it has so many terms associated with them. Decoding a METAR Remarks section is something you’ll want to have a legend of terms to understand, or invest a lot of time memorizing the table.

    Our example means:

    RMK AO2 RAE04 P0000 T02220206

    RMK : Just means this is the Remarks section

    AO2 : Automated & has a precipitation sensor

    RAE04 : Rain Ended at 4 minutes past the hour

    P0000 : Hourly precipitation in hundredths of inches, 0 in this case.

    T02220206: Hourly temperature and dew point in tenths degrees C, 22.2 20.6 in this case.

    The remarks section I use to ‘decode’ the metar remarks is on, and use their abbreviations chart for more in-depth information.


    Reading these METAR weather reports isn’t easy! Especially the remarks section. But In my experience on the Part 107, no tricky questions have been asked about the remarks section of the METAR, only the main part of the report. That being said, I’d still read over the different versions of the METAR remarks and understand what they are saying just to make sure.

    The main structure of the METAR is pretty straightforward after you know how to read the different messages and what to look for, again – other than that stinking remarks section! What is the toughest part of a METAR report for you to read?

    The current energy efficiency addin tool for Revit is called Autodesk Insight. It has a couple of tools to measure different energy efficiency ideas. I’ll be looking at doing a Day lighting analysis in this blog.


    First step is to download the Insight Revit add in. The addin can be downloaded by visiting the main Insight website:

    Then select the Download tab.

    How to analyze a cloud in the sky

    In the download tab you can then download the appropriate addin version. In this case we downloaded the Revit 2020 addin.

    How to analyze a cloud in the sky

    Once downloaded install the add in. Just make sure Revit is closed when installing.

    How to analyze a cloud in the sky

    Once installed you can open Revit and when going to the Analyze Tab you’ll see the Insight panel.

    How to analyze a cloud in the sky

    Model Preparation.

    In order to do a day lighting analysis you need to make sure the ‘sun’ is in the correct position. To do so you need to first locate your project in the world and then orientate your project in relation to North.


    To locate your project, select the Manage Tab and Location as shown.

    How to analyze a cloud in the sky

    A dialogue box will appear in which you can add the Project address. Add your address. In this case I used the standard one for this project which is Boston in the USA.

    How to analyze a cloud in the sky

    Then make sure that the sun orientation is set up on your project. To do this go to the project’s Site View. In the View Properties set the Orientation Parameter to True North.

    How to analyze a cloud in the sky

    Once set go to the Manage Tab and select Rotate True North tool as shown.

    How to analyze a cloud in the sky

    Add the angle that the Project North and True North differ. In this case its 37 degrees.

    How to analyze a cloud in the sky

    How to analyze a cloud in the sky

    Once this is set the Project is set so that North is pointing upward and that allows the sun to be in the correct orientation.

    Day lighting

    Go to the Analyze Tab and the select the Lighting tool. Then in the next dialogue box click Go.

    How to analyze a cloud in the sky

    This will open the Lighting Analysis in the Cloud dialogue box. It might do a license checking first to see if you have access to this service. Insight Cloud service is part of the Autodesk AEC collection Subscription.

    The next dialogue box will allow you to select a analysis to run and time to use. I left all default and selected Start.

    How to analyze a cloud in the sky

    You’ll receive a confirmation that the Model is busy uploading.

    How to analyze a cloud in the sky

    Once processed you’ll be presented by the report which you can then accept.

    How to analyze a cloud in the sky

    You can then save the Project.

    How to analyze a cloud in the sky


    Now go to one of the plans and select the Lighting tool again. Select the drop down and pick Generate Results. Select Go.

    How to analyze a cloud in the sky

    This will generate plans and a 3D of the results. Select the Lighting plan. You’ll see a visualisation of the lighting lux levels. Note you can move the lux level legend.

    How to analyze a cloud in the sky

    In the 3D view I used a section box to remove the roof to reveal the floor visualisation.

    How to analyze a cloud in the sky

    Also note you can select the visualisation object and in the Properties set the time and/or averages.

    How to analyze a cloud in the sky

    You can also Edit the Style of the visualisation. Select the visualisation object and then select Edit Style in the ribbon. You can set the Style or edit the colour of the visualisation.

    How to analyze a cloud in the sky

    You can also change the style.

    How to analyze a cloud in the sky


    Using this tool assist the designer to very quickly visualise and see the effect of the sun at various times and the effects of their window positions, for example.

    Can you locate the Big Dipper tonight? How about the constellation Hercules? The articles below will provide a few astronomy basics, which will help you to get your bearings on the heavens so that star patterns and constellations will become your familiar friends, allowing you to find observing targets with ease.

    With the right “road map to the stars,” (a.k.a. one of our free star charts) you’ll be able to use your base knowledge to find interesting stellar pairings and locate “deep-sky objects” — the star clusters, galaxies, and nebulas that binoculars and telescopes will reveal. Once you’ve found the Big Dipper, it’s easy to find two binary pairs. Similarly, once you know the Hercules constellation, it’s easy to find the globular cluster hidden within.

    No one can help you learn your way around the night sky like Sky & Telescope can.

    How to analyze a cloud in the sky

    See the Sun from Other Stars

    We journey to distant suns to look back at our solar system and see its place among the stars.

    How to analyze a cloud in the sky

    The Big Dipper: Hop to Spring’s Sky Sights

    The Big Dipper is one of the most familiar sights in the Northern Hemisphere’s night skies. You can use its stars to locate other fun targets.

    How to analyze a cloud in the sky

    A Quick Tour of Orion, the Hunter

    The evening sky this week presents a near perfect opportunity to explore winter’s marquee constellation, Orion, with binoculars or a small telescope.

    How to analyze a cloud in the sky

    Astronomy for Beginners: How to Get Started in Backyard Astronomy

    Astronomy doesn’t deserve its reputation as a tough, expensive hobby. You just need to begin with the right advice.

    How to analyze a cloud in the sky

    Astronomy Books: Wrapping Up 2017

    Wondering what to read next? Looking for a gift for the amateur astronomer in your life? Check out these new astronomy books!

    How to analyze a cloud in the sky

    Native American Full Moon Names

    Native American tribes each had their own full Moon names — we introduce the most commonly used ones and the traditions behind them.

    How to analyze a cloud in the sky

    Stargazing Simplified: What to See in the Night Sky Tonight

    Learn some of the classic stargazing sights that can be best viewed through a smaller telescope.

    How to analyze a cloud in the sky

    Learn Constellations with a Planisphere

    How do you find out what stars are visible tonight? With a planisphere or “star wheel.” It’s easy!

    How to analyze a cloud in the sky

    How to Use a Star Chart with a Telescope

    Here’s what you need to know to navigate the heavens with a telescope and star atlas.

    How to analyze a cloud in the sky

    Star Charts: A Vital Resource for Learning the Night Sky

    Our Constellation Basics webinar provides background information about the major winter constellations. Here are some accompanying online resources.

    How to analyze a cloud in the sky

    Asterisms for Winter Nights

    Asterisms appeal to our playful side but also serve as key waypoints in the sky for identifying fainter stars and constellations.

    How to analyze a cloud in the sky

    Earthshine, the Moon’s Darker Side

    With a subtle beauty all its own, the earthshine we see glowing in the lunar night invites us to consider Earth’s many connections to the Moon.

    How to analyze a cloud in the sky

    Video: Using Star Charts and Star Wheels

    Watch S&T senior editor Alan MacRobert show and explain how to use star charts and planispheres (star wheels).

    How to analyze a cloud in the sky

    How to Make a Star Wheel the Simple Way

    Would you like to be able to navigate your way around the night sky with confidence? Using this simple, easy-to-make Star Wheel, you can “dial the sky” for any time or date.

    How to analyze a cloud in the sky

    Astronomy for Beginners: Getting Started in Astronomy

    An easy guide to exploring the universe is just a quick download away. This PDF document contains valuable tips for beginner stargazers, a detailed Moon map, and six bimonthly star charts for either the Northern or Southern Hemisphere.

    How to analyze a cloud in the sky

    Fuzzies in Your Future:
    An Introduction to Deep-Sky Objects

    Ready to voyage beyond the Solar System? Here’s what you can see.

    How to analyze a cloud in the sky

    Names of Deep-Sky Objects

    Expert observer Brian Skiff explains NGC, UGC, and everything in between.

    How to analyze a cloud in the sky

    Star Names: Where Do They Come From and What Do They Mean?

    Confused by the bizarre names that astronomers have given the stars? Here’s where they come from and what they mean.

    You probably don’t get to stare at the night sky very often. I know I don’t. With all the late-night shifts, regularly replaced by sleeping on time to attend a morning lecture, it’s been a while. But this was not always the case with our ancestors.

    They wondered a lot. They observed a lot more. Greek travelers staring into the night sky cooked up all sorts of stories about what the stars meant and represented. They used stars for navigations; medieval versions of Google Maps.

    Particularly, they used constellations of stars. Out of 88 of these constellations, Orion is one of the most famous. It’s a bunch of stars that together, look like a hunter with a club and a shield.

    Orion, in Greek mythology, was a giant hunter. He was the son of the water God Poseidon and King Minos’ daughter. He was killed by a giant scorpion and placed amongst the stars on behest of his lover.

    But what gets this constellation the fame that it has is the rarity that we see in the three stars in the middle of the constellation.

    Seemingly arranged in a completely straight line, these stars look like the hunter’s belt. Thus the name, “ Orion’s belt .”

    This belt is what makes Orion so easy to locate in the night sky. Just look for three stars closely together in a straight line and voila, you’ve located Orion constellation.

    Another easy method to locate this constellation is to look for the armpit and the knee. These two stars are particularly bright; and the ‘armpit’ has a red color. But this article is just about Orion’s belt.

    Let’s leave the rest to another time, some other day.

    Right now, let’s focus on Orion’s belt made by three stars.

    How to analyze a cloud in the sky


    As apparent from the image attached, Mintaka is the top-most or the Western star of Orion’s belt. It’s not really a star but rather a system of multiple stars that are so close together that it appears as one singular entity.

    But note that on a cosmic scale, “close together” means a few light-years away. That’s how far light spreads and when it finally reaches us, it appears as one bright dot. The primary star in this system is called Mintaka Aa1.

    It’s 24 times as heavy as our sun. The biggest part of the Mintaka star system is a set of two stars that orbit each other almost every 6 days. But there are a total of four that constitute the system.

    Some astrophysicists, however, only consider Mintaka to be constituted by the two major stars we just talked about; a class 9.5 giant star and B main-sequence star. In either case, the complete system that we observe as Mintaka is about 1200 light-years away from us, and has been the guiding compass for ancient travelers for centuries.

    How to analyze a cloud in the sky

    Mintaka in Orion (Delta Orionis). Photo by Fred Espenak .


    Mintaka was 1200 light-years away from us. Alnitak is 1260 light-years away. So, they’re not really that far away from each other. Just like Mintaka, it’s not a single star. It’s a system of three different stars locate.

    Alnitak has a characteristic bright blue color. This color is caused by a blue supergiant, Anitak A, which is the primary star of the system. It happens to be a class O supergiant – some of the brightest stars visible in the night, and it’s around 30 times as big as our sun.

    But while it may be the star of the show (pun intended), it can’t overshadow Alnitak Ab, a 7.2 million-year-old blue dwarf, probably the oldest star in Orion’s belt.



    It just keeps getting better. Alnilam is the Eastern-most star of Orion’s belt and happens to be the 29th brightest stars visible in the night sky. It’s around 60 times as massive as our sun.

    While it may be … huge as heck, it’s still relatively young. The star is estimated to be 5.7 million years old, way younger than mammals and Earth.

    The stars in Orion’s belt are all probably twins, on a cosmic level of course; meaning that they were born around the same time and formed from the plasma clouds within the same region that we now know as Orion’s belt.

    Considering Alnilam’s size and trajectory of expansion, it is estimated to turn into a red giant and explode in the future. But there’s nothing new about it, stars explode all the time. Even our sun will explode some time as well.

    But before it does, we’ll get to see our possible doom in Orion’s belt. The explosion will be visible from Earth in the night sky.

    How to analyze a cloud in the sky

    Orion Star Chart including the location of Alnilam in Orion’s Belt. Kim Kaler .

    Deep-Sky Objects

    The Horsehead Nebula , Flame Nebula, and Orion Nebula lie very close to Orion’s Belt in the night sky from our perspective on Earth. The Horsehead Nebula is located just below Alnitak, and the Flame Nebula is directly next to it.

    The Orion Nebula is in “ Orion’s Sword “, below the belt of Orion. Together, these deep-sky objects provide a wonderful opportunity for astrophotography with a wide-field telescope or telephoto camera lens.

    How to analyze a cloud in the sky

    The Deep-Sky Objects surrounding Orion’s Belt.

    You can use the three bright stars in Orion’s Belt to help you find other noteworthy stars in the night sky. For example, by following a straight line in either direction of the belt stars, you will find Sirius on one side, and Aldebaran in Taurus on the other.

    Every time you look up at the sky and notice Orion’s belt, you are looking back in time at distant stars that are more than a thousand light-years away.

    Ever wonder what the difference is between the weather being partly cloudy versus mostly sunny?

    Or… mostly cloudy versus partly sunny?

    How to analyze a cloud in the sky

    The Short Story…

    Most people have their own notions about what partly cloudy versus partly sunny means.

    • Partly Cloudy: About 30% to 70% of the sky is covered with clouds BUT usually refers to sky conditions at night.
    • Partly Sunny: About 30% to 70% of the sky is covered with clouds BUT refers only to sky conditions in the daytime.

    How to analyze a cloud in the sky

    The Long Version…

    So, now you know.

    Partly cloudy mostly refers to sky conditions at night, and partly sunny emphasizes sky conditions in the daytime — although it’s acceptable to use partly cloudy for sky condition observations in the day, too.

    • Partly cloudy and partly sunny mean exactly the same thing — between 3/8 and 5/8 of the sky is covered by clouds. Sometimes, a “mix of sun and clouds” is used by some weather forecasters instead of “partly sunny” during the daytime hours, although that is not an official National Weather Service term.
    • Mostly cloudy means there are more clouds than sun (or stars, at night) — 3/4 to 7/8 of the sky is covered by clouds. This can also be referred to as “considerable cloudiness.”
    • Mostly sunny means there is more sun than clouds (or mostly clear, at night) — 1/8 to 1/4 of the sky is covered by clouds.
    • Sunny or clear means there are no clouds in the sky.
    • Cloudy means the entire sky is covered by clouds.

    How to analyze a cloud in the sky

    Why Is Cloud Coverage Measured In Eighths?

    • 0 oktas means the sky is clear.
    • 4 oktas means half of the sky is cloudy.
    • 8 oktas means the sky is covered with clouds.

    Check out this video time lapse of a partly cloudy day:

    Clouds are condensed droplets or ice crystals from atmospheric water vapor. Clouds form by the rising and cooling of air caused by convection, topography, convergence, and frontal lifting. Convection occurs when the Sun’s radiation heats the ground surface, and warm air rises, cooling as it goes. Air also is cooled if an air mass is forced to move upward as a result of higher topography (e.g., a mountain range) in a process known as orographic lifting. Interestingly, when the air mass descends on the other side of the mountain, it warms and the clouds may disappear as the droplets transfer back to vapor. *

    The counterclockwise motion of a low-pressure center draws air inward, and the convergence forces the air upward. Air also is lifted and cooled along either a cold front or a warm front. A cold front is the leading edge of an air mass that is colder than the air it is replacing. The front forms a wedge that pushes under the warmer air ahead, lifting it. A warm front is the leading edge of an air mass warmer than the air it is replacing. As the air mass pushes forward, the warm air slides up over the wedge of cold air ahead of it, as shown in the following figure.

    Classification of Clouds

    Clouds are classified based on their shape and the height of the cloud’s base above the ground. The most common shapes are cirriform, appearing feathery or fibrous; stratoform, appearing layered; and cumuloform, appearing as if piled up. Two additional words used to describe clouds are “nimbus,” meaning rain, and “alto,” meaning middle. Basic cloud types are based on height above the land surface and on the cloud’s vertical development, as summarized below.

    • High clouds (cloud base above 7 kilometers or 23,000 feet). Usually consisting of ice crystals, these include cirrus, cirrostratus, and cirrocumulus.
    • Middle clouds (2 to 7 kilometers or 6,500 to 23,000 feet). Consisting of liquid droplets, these include altocumulus and altostratus.
    • Low clouds (below 2 kilometers or 6,500 feet). Consisting of liquid droplets, these include stratus, stratocumulus, and nimbostratus.
    • Clouds of vertical development (cloud base generally is in the low cloud range, but the tops may reach great heights). These include cumulus clouds and the towering cumulonimbus. *

    Fog represents a special case of cloud-like formation. Although not truly a cloud, fog is essentially stratoform clouds on the ground.

    Cumulus Clouds.

    Cumulus clouds are among the most interesting in terms of their shapes, which stir peoples’ imagination and allow them to see a variety of “objects” or “scenes” in the sky. All cumulus clouds have two characteristics in common. They tend to be bulbous or popcorn-like on top, and have relatively flat bottoms. Why do they all share these features?

    Cumulus clouds are classified as clouds of vertical extent. They form as air moves vertically, cooling until the water vapor in the air condenses. This vertical movement is the key to understanding the flat-bottomed character of these clouds. In a given area, for a given air mass, it is common to find that the cooling rate of ascending air is relatively constant. In other words, rising air will cool to a certain temperature at the same height above the ground throughout the area. Air moving vertically in that area will reach the condensation temperature at the same height above the ground and cloud formation will begin at that height. Consequently, the base of the cloud will be at the same height throughout and the cloud’s base will appear flat.

    As the air continues to rise and water vapor continues to condense, the cloud will extend vertically. The column of rising air actually consists of a number of currents with slightly different directions and may move as pulses. These currents move upward as they condense and give rise to the apparently independent bulbous lobes of the cloud.

    Precipitation Types

    Precipitation elements begin to form in the part of the cloud where ice crystals and cloud droplets coexist. Most precipitation starts out as snow, except for rain that comes out of very low clouds. Precipitation will remain snow unless it falls through a layer of warmer air, in which case it will melt and remain rain unless it falls through a colder layer of air, where it may freeze and become sleet or ice pellets (as shown in the following figure). When the air at the ground level is below freezing, the raindrops can freeze when they hit the ground or other cold surfaces: it is then called freezing rain.

    How to analyze a cloud in the sky

    Hail is formed when a particle, like dust, attracts a drop of moisture to itself. The particle gets blown upward by strong updrafts in the cloud, and freezes as it goes through a colder layer of air. It is heavier and begins to fall, attracts more moisture and then gets forced upward again and again adding more frozen layers.

    The varying intensities of rainfall have specific names. Liquid precipitation that is of a longer duration and larger drop size is called rain; when it falls in shorter spurts it is called a shower. Rain typically falls from lowlevel stratoform clouds with greater vertical extent. When the drops are very small, rain is called drizzle. A raindrop is about 1,000 times larger than drizzle.


    Thunderstorms go through stages of development from the beginning cumulus stage, when the cloud starts to grow vertically; to the mature stage, when heights may reach from 12 to 18 kilometers (8 to 11 miles); to the dissipating stage (see figure below).

    In the cumulus stage, there is an updraft of warm air throughout the cloud, as shown in part (a) of the figure. As the warm updraft increases, the

    How to analyze a cloud in the sky

    As the updraft pulls more dry air into the cloud, some of the raindrops evaporate, and the air cools, making it colder and heavier than the surrounding air. This usually strengthens the downdraft. The falling precipitation causes more downdrafts to form throughout the cloud, beginning the dissipating stage, as shown in part (c) of the figure. During the dissipating stage, precipitation occurs from the entire cloud base.

    Some thunderstorms can develop into lines of severe thunderstorms, producing high winds, hail, frequent lightning, heavy rain, flash floods, and even tornadoes.

    Timothy A. Chuey

    and Dennis O. Nelson


    Ahrens, C. Donald. Meteorology Today. St. Paul, MN: West Publishing, 1985.

    Internet Resource

    “Clouds and Precipitation.” WW2010 Weather World Project, Department of Atmospheric Sciences, University of Illinois at Urbana-Champaign. .

    * See “Climate Moderator, Water as a” for a diagram of orographic lifting and the rain shadow effect.

    * See “Precipitation, Global Distribution of” for a photograph of a cloud of vertical development.

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