HR: 16:24h
AN: A44A-03    [Abstracts]
TI: Two year trend analysis of AIRS and AMSU data over cloud-free tropical oceans for climate applications
AU: * Aumann, H H
EM: aumann@jpl.nasa.gov
AF: Jet Propulsion Laboratory California Institute of Technology , 4800 Oak Grove Drive, Pasadena, CA 91109 United States
AU: Gregorich, D T
EM: dtg@airs1.jpl.nasa.gov
AF: Jet Propulsion Laboratory California Institute of Technology , 4800 Oak Grove Drive, Pasadena, CA 91109 United States
AB: We present the analysis of two year of trends in AIRS and AMSU data. AIRS is a hyper-spectral infrared sounder and AMSU is a microwave sounder on the EOS Aqua satellite, which was launched into 705 km altitude sun-synchronous orbit in May 2002. Both instruments are cross-track scanners, with synchronized scan coverage. Instrumentation on polar orbiting satellites is ideally suited to the global monitoring of environmental variables. Since the predicted effects of global changes require measurement accuracy and stability at the faction of a degree Kelvin per year level, validation and trend analysis of the data are critical to characterize their applicability to climate research. The AIRS radiances are based on a NIST traceable onboard calibration blackbody. These radiances are tied via the 2616cm-1 window channel to the Real Time Global SST, RTGSST. The RTGSST, generated daily by NCEP for the GCM in support of weather forecasting, provides the tie of the AIRS calibration to the global network of drifting buoys, which serve as quasi tertiary standards. Analysis of the AIRS 2616 cm-1 based sea surface temperature measurements relative to the RTGSST shows better than 7mK per year radiometric stability, with a residual cold bias of 200mK. The radiometric stability for all AIRS channels is established through the common onboard blackbody and space view. The radiometric stability of AMSU was tested by comparing the brightness temperatures measured by AMSU channel 5 at 53 GHz with co-located measurements by the AIRS 2388cm-1 channel. The two channels sound at 5 km altitude in the mid-troposphere with closely matching weighting functions, but the microwave opacity is due to oxygen, while the infrared opacity is due to co2. The comparison was limited to cloud-free tropical oceans with less than 35 degree slant path. Analysis of two years of data shows that the brightness temperatures measured by AIRS 2388cm-1 channel are slowing getting colder relative to the AMSU channel 5 temperatures at the rate of about 100mK/year. The interpretation of this relative cooling as co2 increase at the rate of about 2.2 ppmv/year is supported by the presence of the expected seasonal co2 abundance maxima in May 2003 and May 2004. This result, which is the first measurement of the global increase in co2 using the AIRS and AMSU on EOS Aqua, is an important step in confirming the potential value of the data to climate research.
DE: 1600 GLOBAL CHANGE (New category)
DE: 1640 Remote sensing
DE: 0300 ATMOSPHERIC COMPOSITION AND STRUCTURE
DE: 0933 Remote sensing
SC: Atmospheric Sciences [A]
MN: 2004 AGU Fall Meeting