Intercomparison of the 11- and 12-μm bands of Terra and Aqua MODIS using NOAA-17 AVHRR

Abstract

Nearly identical copies of the MODerate Resolution Imaging Spectroradiometer (MODIS) are currently operating onboard the NASA s Earth Observing System (EOS) Terra and Aqua satellites launched on December 18, 1999 and on May 04, 2002 respectively. MODIS has 36 spectral bands with wavelengths from 0.41 to 14.5 μm. Bands 1 - 19 and 26 are the reflective solar bands (RSB) with spectral wavelengths from 0.41 to 2.2 μm and bands 20 - 25 and 27 - 36 are the thermal emissive bands (TEB) with spectral wavelengths above 3.5 μm. The two latest Advanced Very High Resolution Radiometer (AVHRR) instruments were launched onboard the NOAA-16 and NOAA-17 on September 21, 2000 and on June 24, 2002 respectively. The new AVHRR/3 instrument (onboard NOAA-15 to -17) is a six-channel imaging radiometer in the visible and infrared spectral region. There have been many important parameters and science products derived from observations made by both MODIS (more data products) and AVHRR (longer data record). In this paper, we present an inter-comparison of the 11 μm and 12 μm bands of the Terra and Aqua MODIS (bands 31 and 32) using the NOAA-17 AVHRR (channels 4 and 5). The AVHRR is served as an intermediate transfer vehicle. The intercomparison data sets from the MODIS and AVHRR are selected from nearly simultaneous observations (within 30 seconds) over relatively uniform scenes near the instrument nadir view with pixel-by-pixel matches in the Polar region. Preliminary results show that the measured temperature differences between the Terra and Aqua MODIS at 11 μm and 12 μm are about 0.25 K and 0.35 K at a brightness temperature of about 250 K, indicating consistent and reliable on-board calibration and characterization for the MODIS instruments. Using the same approach this paper also presents the results from comparing the NOAA-16 and 17 AVHRR 11 μm and 12 μm channels. At a brightness temperature range from 240 to 270 K, the observations show that the NOAA-17 AVHRR is about 0.45 K cooler than the NOAA-16 AVHRR for its 11 μm and 12 μm channels.