This image shows average daytime temperatures in May, 2009, as observed by
AIRS, the Atmospheric Infrared Sounder (AIRS) on NASA's Aqua satellite.
Similar to a what a photograph of the planet taken with the camera shutter
held open for a month would show, stationary features are captured in
sharp detail while those obscured by moving clouds are blurred. Much of
the Antarctic is above 3,000 meters (10,000 feet) and is therefore blacked
out in this image. (Where there are high mountains of smaller extent, such
as the Andes, the image is based on an “interpolation” from surrounding
areas.)
AIRS can retrieve temperature data from different levels in the
atmosphere. The temperatures you see here are found at an atmospheric
pressure level of 700 millibar, which occurs at approximately 3,000 meters
(10,000 feet) altitude. This level of the atmosphere is located in the
upper reaches of the lower troposphere, and the display of warm air
masses, cold air masses, and frontal boundaries is particularly vivid. The
deepest reds represent relatively warm air found in the tropics and above
some desert areas. The darkest blues and purples represent below-freezing
temperatures that are found in the polar regions, especially at the
Antarctic—where it is near mid-winter in May. The color scale has
been chosen to emphasize temperatures just below freezing. The freezing
level typically occurs at 700 mb at mid-latitudes, where clouds and storms
are prevalent, and the image illustrates the somewhat chaotic picture that
emerges there when averaged over a month. This is a reflection of the
dynamic nature of the atmosphere in those regions.
The AIRS Public Web site can be found at http://airs.jpl.nasa.gov.
AIRS, in conjunction with the Advanced Microwave Sounding Unit (AMSU) also
on Aqua, sense emitted infrared and microwave heat radiation from Earth to
provide a three-dimensional look at Earth's weather and climate. Working
in tandem, the two instruments can make simultaneous observations all the
way down to Earth's surface, even in the presence of heavy clouds. With
more than 2,000 channels sensing different regions of the atmosphere, the
system creates a global, 3-D map of atmospheric temperature and humidity,
cloud amounts and heights, greenhouse gas concentrations and many other
atmospheric phenomena. AIRS and AMSU are managed by NASA's Jet Propulsion
Laboratory, Pasadena, Calif., under contract to NASA's Science Mission
Directorate, Washington. JPL is a division of the California Institute of
Technology in Pasadena.