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Have you ever been in a situation where the weather forecast called for sunny skies, yet

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it ended up raining all day long?

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You think, oh, if I only had my umbrella.

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But you know, guys, the job of predicting weather accurately is a difficult one, because

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our atmosphere, it's constantly changing.

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You see, in order to predict the weather accurately for the hours and days ahead, weather forecasters

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must analyze information they receive from a number of sources, including local weather

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observers, weather balloons, weather stations, and satellites.

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Speaking of satellites, NASA has a train of satellites called the Afternoon Constellation,

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nicknamed the A-Train, which are orbiting the Earth, and they're collecting all sorts

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of data, including data that will help predict weather and climate change.

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Two additional satellites, CloudSat and CALIPSO, will soon be launched to be a part of that

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train.

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CloudSat will help improve weather prediction by studying the different aspects of clouds,

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as its name implies.

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CALIPSO will help predict climate change and how aerosols or particles affect the Earth's

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atmosphere.

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Later on in the program, Dr. Didier Tonray will tell us all about aerosols.

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But first, let's visit with Dr. Graham Stevens.

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He's the principal investigator on the CloudSat mission.

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Thank you, Jennifer.

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We rely on accurate weather predictions for many activities.

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Farmers need to know the best times to plant and harvest their crops.

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Airplane take-offs, landings, and flight paths are scheduled according to local weather conditions.

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Weather forecasts alert people to severe storms that could endanger life or property, and

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most people want to know what the weather will be like as they go to and from work and

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school or plan outdoor activities.

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But do you think weather predictions or forecasts are always correct?

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What do you think causes errors in weather forecasts?

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You know, Jennifer is right when she stated that weather prediction is difficult.

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The atmosphere is constantly changing, and even though we receive weather data from a

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variety of sources, such as weather stations, satellites, weather balloons, and ground-based

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observers, it is still impossible to predict the weather correctly 100% of the time.

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One of the ways of improving our prediction of weather and climate is to develop new technologies

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that helps us understand how the atmosphere works.

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A new satellite that will help improve weather prediction is NASA's CloudSat satellite.

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CloudSat will provide the first vertical cloud profiling from space, improving weather and

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climate forecasts.

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Before we continue with the specifics of the CloudSat mission, here are a few questions

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I would like you and your peers to discuss and answer.

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What is a cloud?

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What types of clouds exist?

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Which clouds make which weather?

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Why is it important to study clouds?

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It's now time to pause the program.

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So how did you do with your questions?

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You know, clouds are all made of water.

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Sometimes they are made of tiny drops, far apart and held up by the wind.

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Other times they are made of big drops, held up for a while by very strong upward winds

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inside the cloud.

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In this kind of cloud, the drops become too heavy to stay up, so they fall to earth as

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rain, or if it's cold enough, they fall to earth as snow, hail, or sleet.

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Clouds are classified based on three factors, their shape, the altitude at which they occur,

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and whether they are producing precipitation.

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Clouds come in three basic shapes, cumulus clouds, which are heaped and puffy, stratus

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clouds, which are layered, and cirrus clouds, which are wispy.

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Clouds also occur in three altitude ranges, specifically the altitude of the cloud base.

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High clouds, which occur above 6,000 metres and designated by cirrus, or cirro, are cirrus,

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cirrocumulus, and cirrostratus.

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Low clouds, which occur between 2,000 and 6,000 metres and are designated by alto, are

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altocumulus and altostratus.

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Low clouds, which occur below 2,000 metres, are stratus, nimbostratus, cumulus, stratocumulus,

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cumulonimbus, and fog.

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I bet you didn't think fog was a cloud.

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It's a cloud that touches the ground.

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Clouds that incorporate the word nimbus, or the prefix nimbo, are clouds from which

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precipitation is falling.

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Can you think of another type of cloud?

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I'll leave the answer to that question up to you.

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So how many of you are wondering how to keep all those clouds in order?

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You know, it's tough even for me.

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That's why I use this globe cloud chart as a reference.

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You'll learn more about globe later in the program.

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So why is it important to study clouds?

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Clouds exert an enormous influence on our weather and climate.

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They are nature's way of moving fresh water from place to place on Earth.

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Clouds play a very important part in maintaining Earth's temperature.

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We need to understand how clouds reflect the sun's energy back into space or trap the Earth's

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energy in the atmosphere.

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We call this Earth's radiation budget.

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Using the CloudSat satellite, for the very first time, we'll be able to measure the altitude

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and properties of clouds.

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CloudSat radar will slice through the atmosphere, providing vertical cross-sectional view of

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clouds and furnish new weather and climate data, including cloud layer thickness, cloud

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top and base altitude, and water and ice contents.

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Existing space-based systems only observe the uppermost layer of clouds and cannot reliably

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detect the presence of multiple cloud layers, nor determine the cloud water and ice content.

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The penetration of CloudSat's radar into and through clouds will yield a new capability

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that fills a critical gap in existing and planned space-borne observational systems.

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With this new technology, CloudSat will improve weather predictions, increasing the accuracy

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of severe weather, hurricanes and flood warnings.

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And now Jennifer, I think the students are ready to size up the clouds.

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Back to you.