Feature

Why Does NASA Have Its Head in the Clouds?
10.16.03
picture of cumulus clouds
This picture of a developing cumulus congestus cloud was taken in Virginia
Clouds are more than just funny shapes or pretty pictures. They also play a critical role in the Earth's energy and water cycles, and thus the Earth's climate.

Determining exactly how clouds affect climate is a difficult task. For example, during the day clouds block sunlight from reaching the ground, producing a cooling effect. But at night they prevent heat from escaping to space, producing a warming effect. To make things more complicated, not all clouds behave the same - high clouds affect temperature differently than low clouds, and thick storm clouds affect temperature differently than thin clouds.

Understanding the impacts of all kinds of clouds is an important key to predicting how Earth's climate will change in the future. One of the biggest sources of uncertainty in the computer programs that predict climate is the effects of clouds.

picture taken in Taiwan of nimbostratus clouds
Low nimbostratus clouds with rain shafts are visible in this picture taken in Taiwan
That's why NASA launches satellites into space that are specifically used to study clouds. Some of these satellites simply take pictures of clouds, while others send invisible pulses into the clouds to measure various properties, such as cloud thickness or water content.

An instrument called CERES, which stands for Clouds and the Earth's Radiant Energy System, is currently onboard several NASA satellites orbiting Earth. CERES measures the amount of energy reflected and emitted by clouds at different heights in the atmosphere. This information is then entered into climate models to improve their accuracy.

Satellite measurements themselves aren't always accurate, however. With that in mind, NASA's Students' Cloud Observations On-line (S'COOL) program allows K-12 students to help NASA scientists calibrate CERES instruments. When a satellite carrying CERES is scheduled to pass overhead, participants record their observations of cloud cover, type, height and thickness. By comparing CERES measurements from space with what students see from the ground, scientists can assess the instrument's performance and make any necessary adjustments.

picture of nimbostratus clouds
Nimbostratus clouds in West Virginia
CERES is just one of several instruments on the Tropical Rainfall Measuring Mission (TRMM) satellite. TRMM, a joint mission between NASA and Japan's National Space Development Agency (NASDA), is designed to monitor and study tropical clouds and rainfall. The energy associated with this rainfall is largely responsible for driving global atmospheric circulation.

NASA's Terra and Aqua satellites also carry CERES and other instruments that are continuously gathering information on all aspects of clouds. CloudSat and CALIPSO, NASA's newest cloud-observing satellites, are scheduled for launch in 2004.

Resources

Students' Cloud Observations On-line (S'COOL)
http://asd-www.larc.nasa.gov/SCOOL

CERES Web site
http://asd-www.larc.nasa.gov/ceres/ASDceres.html

TRMM Web site
http://trmm.gsfc.nasa.gov

Aqua Web site
http://aqua.nasa.gov

Terra Web site
http://terra.nasa.gov