Four images of the Mediterranean obtained concurrently on June 14, 2002
from the three instruments that make up the Atmospheric Infrared Sounder
experiment system aboard NASA's Aqua spacecraft. The system features
thousands of individual channels that observe Earth in the visible,
infrared and microwave spectral regions. Each channel has a unique
sensitivity to temperature, moisture, surface conditions and clouds.
This visible light image from the AIRS instrument shows a band of white
clouds extending from the Adriatic Sea over Greece to the Black Sea.
The AIRS image (figure 1) at 900 cm-1 (11 micrometers) measures actual
surface or cloud top temperatures. In it, land and ocean boundaries are
well defined, with land appearing as warmer (darker red) than the ocean.
The band of cold high cumulus clouds appears blue, with the darkest blue
most likely a large thunderstorm.
The 150 gigahertz channel from the Humidity Sounder for Brazil instrument
(figure 2) is sensitive to moisture, ice particles and precipitation. The
dry land temperature is comparable to the 11 micrometer temperatures, but
over ocean this channel measures the temperature of moisture in the mid
troposphere. The cold, blue areas off Sicily and in the Aegean Sea
represent unusually dry areas over the ocean. There, clouds appear as
green filaments--likely areas of precipitation.
The 31.4 gigahertz channel from the Advanced Microwave Sounding Unit
instrument (figure 3) is not affected by clouds.
NASA's Atmospheric Infrared Sounder (AIRS) onboard NASA's Aqua spacecraft,
began sending high quality data on June 12, 2002. This "first light" data
is exceeding the expectations of scientists, confirming that the AIRS
experiment is well on its way to meeting its goals of improving weather
forecasting, establishing the connection between severe weather and
climate change, determining if the global water cycle is accelerating,
and detecting the effects of increased greenhouse gases.
The AIRS sounding suite is a tightly integrated remote sensing system
that will be used to create global three-dimensional maps of temperature,
humidity and clouds in the Earth's atmosphere with unprecedented accuracy.
This will lead to better weather forecasts as well as a wealth of data
that will be used to study and characterize and eventually predict the
global climate. The AIRS system is made up of three of the six Aqua
instruments - AIRS itself, which is an infrared sounder with an
unprecedented 2378 spectral channels, complemented with a 4-channel
visible/near-infrared imaging module; AMSU-A, which is a 15-channel
microwave temperature sounder; and HSB, which is a 4-channel microwave
humidity sounder. These instruments are carefully aligned with each other
and scan the atmosphere in a synchronized way, giving us simultaneous
multispectral views of a highly variable target.
The Atmospheric Infrared Sounder is an instrument onboard NASA's Aqua
satellite under the space agency's Earth Observing System. The sounding
system is making highly accurate measurements of air temperature, humidity,
clouds and surface temperature. Data will be used to better understand
weather and climate. It will also be used by the National Weather Service
and the National Oceanic and Atmospheric Administration to improve the
accuracy of their weather and climate models.
The instrument was designed and built by Lockheed Infrared Imaging
Systems (recently acquired by British Aerospace) under contract with
JPL. The Aqua satellite mission is managed by NASA's Goddard Space
Flight Center.
