Evaluation of AIRS, MODIS, and HIRS 11 micron brightness temperature difference changes from 2002 through 2006

摘要

In an effort to validate the accuracy and stability of AIRS data at low scene temperatures (200-250 K range), we evaluated brightness temperatures at 11 microns with Aqua MODIS band 31 and HIRS/3 channel 8 for Antarctic granules between September 2002 and May 2006. We found excellent agreement with MODIS (at the 0.2 K level) over the full temperature range in data from early in the Aqua mission. However, in more recent data, starting in April 2005, we found a scene temperature dependence in MODIS-AIRS brightness temperature differences, with a discrepancy of 1-1.5 K at 200 K. The comparison between AIRS and HIRS/3 (channel 8) on NOAA 16 for the same time period yields excellent agreement. The cause and time dependence of the disagreement with MODIS is under evaluation, but the change was coincident with a change in the MODIS production software from collection 4 to 5. AIRS and MODIS (Flight Model 1) are onboard the EOS Aqua spacecraft, launched into a 1:30 PM polar orbit on May 4, 2002. AIRS has 2378 infrared channels with high spectral resolution (1200) covering the 3.7 to 15.4 micron wavelength range, with a nominal spatial resolution of 13.5 km. MODIS has 36 relatively broad spectral bands with spatial resolution of 1 km for the LWIR bands. HIRS/3 is onboard NOAA-16 (L), launched into a 2:00 PM polar orbit on Sep. 21,2000.