The Advanced Technology Microwave Sounder (ATMS), a cross-track scanner with 22 channels, provides sounding observations needed to retrieve profiles of atmospheric temperature and moisture for civilian operational weather forecasting as well as continuity of these measurements for climate monitoring purposes. Like the long heritage of its predecessors, ATMS combines all the channels of the preceding AMSU-A1, AMSU-A2, and AMSU-B sensors into a single package with considerable savings in mass, power, and volume.
Like the long heritage of its predecessors, ATMS is a cross-track scanner, but ATMS combines all the channels of the preceding AMSU-A1, AMSU-A2, and AMSU-B sensors into a single package with considerable savings in mass, power, and volume. 22 channels in bands from 23 GHz through 183 GHz are included. ATMS will fly on NPP mission & JPSS (note that there are likely to be subtle differences between the NPP version of ATMS and the JPSS version(s) of ATMS.
The Crosstrack Infrared Sounder (CrIS) and the advanced Technology Microwave Sounder (ATMS) together represent the latest addition to a long series of atmospheric satellite sounders that originated in the late 1970's. CrIS is a hyperspectral sounder that will make it possible to continue the great advances in atmospheric observations and research that started with the Atmospheric Infrared Sounder (AIRS) launched by NASA on the Aqua research satellite in 2002, and ATMS will similarly continue the series of observations that started with the Advanced Microwave Sounding Unit (AMSU) first launched by NOAA in 1998.
Since clouds are mostly opaque in the infrared part of the spectrum while they are largely transparent at microwave frequencies, there is tremendous synergy between the two, and by operating them together as a system it is possible to cover a much broader range of weather conditions than with the infrared sounder alone. The CrIS-ATMS system (called CrIMSS) continues this approach.
The most immediate use of the data from the sounders is in "numerical prediction", which forms the basis for modern weather forecasting. In that application, lightly processed data are immediately "assimilated" into a complex computer model of the atmosphere that is used to extrapolate the current weather into the near future. A large variety of data are used for this purpose, ranging from weather balloon measurements to satellite observations, but the microwave sounders have had the greatest impact on forecast accuracy, with the hyperspectral infrared sounders now a close second. We expect that CrIS and ATMS will continue to play this key role in weather forecasting.
Geophysical parameters derived from AMSU and AIRS data have also been playing an important role in weather and climate research. The primary focus is on research related to the atmospheric components of the "hydrologic cycle", i.e. water vapor, clouds and precipitation. The infrared sounder is generally most accurate and can reproduce the global temperature and humidity distribution as long as it is not too cloudy, while the microwave sounder can provide a picture inside and below the clouds and can also be used to probe into storms, including hurricanes.
In addition, it has turned out that the broad and detailed spectral coverage provided by the hyperspectral infrared sounders has enabled new research related to atmospheric trace gases that play an important role in the global "energy budget", such as carbon dioxide and monoxide, ozone, and methane. We expect that data from CrIS and ATMS will also play a major role in this research.
Climate research naturally progresses from studies of "atmospheric processes" - which typically require small data sets, through studies of "climate variability" - which may require longer time series, to studies of "climate trends" - which may require many years of data. In this progression, the data must be more and more accurate, since the effect being studied is generally of smaller and smaller magnitude.
Therefore, it is of great importance to not only collect and keep the data as it accumulates - to form long time series, but also to "validate" against references that are known to be close to the truth and to "characterize" the inevitable errors in the data. Those tasks are as important as and usually form an integral part of the research.
Similarly, great effort goes into constantly improving the "retrieval systems" that are used to derive geophysical parameters from the raw data. As improvements are made, it is also necessary to reprocess the entire data set that has been accumulated. These apparently mundane tasks - archiving, characterizing, validating, improving, and reprocessing - provide the backbone of the research, and progress will be hindered without them.
The frequency dependence of atmospheric absorption allows different altitudes to be sensed by spacing channels along absorption lines. ATMS has 22 channels, mostly the same as its predecessor with a few modifications/additions.
|Envelope dimensions||70x60x40 cm|
|Operational average power||100 W|
|Operational peak power||200 W|
|Data rate||30 kbps|
|Absolute calibration accuracy||0.6 K|
|Maximum nonlinearity||0.35 K|
|Frequency stability||0.5 MHz|
|Pointing knowledge||0.03 degrees|
Image Above : Microwave images are created when data from NASA's Aqua satellite AIRS and AMSU instruments are combined. This microwave image of Typhoon Mirinae suggests cold, high thunderstorms have developed and an eye is forming. Credit: NASA