Extended Abstract (2.2M)P6.20
Two MODIS aerosol products over ocean on the Terra and Aqua CERES SSF datasets
Alexander Ignatov, NOAA/NESDIS/ORA, Camp Springs, MD; and P. Minnis, N. G. Loeb, B. A. Wielicki, W. F. Miller, S. Sun-Mack, D. Tanre, L. A. Remer, I. Laszlo, and E. B. Geier
NASA Langley Research Center (LaRC) generates Clouds and the Earth's Radiant Energy System (CERES) Single Scanner Footprint (SSF) datasets from the Terra and Aqua satellites (launched in December 1999 and May 2002, respectively). Over ocean, two aerosol products are reported side-by-side, derived from the MODerate resolution Imaging Spectroradiometer (MODIS) using different sampling and aerosol algorithms. The primary M-product is derived from the standard multi-spectral aerosol product developed by the MODIS aerosol group (Tanre et al. 1997; Remer et al. 2004). NASA LaRC receives the 10-km resolution MOD04/MYD04 granules from the NASA Goddard Space Flight Center (GSFC), subsets on aerosol parameters (saving 13 out of 47), and re-maps them into larger-size CERES footprints. In contrast, a simpler secondary (Advanced Very High Resolution Radiometer, AVHRR-like) A-product is fully produced by LaRC on-site with a less sophisticated cloud clearing, and a single-channel aerosol algorithm. Two aerosol optical depths (AOD), tA1 and tA2, are derived from MODIS bands 1 (0.644) and 6 (1.632 µm) resembling the AVHRR/3 channels 1 and 3A, respectively. On Aqua, the retrievals are made in band 7 (2.119 µm) instead of poor quality band 6. From t, the respective Angstrom exponents (AE) are derived, a=-ln(t1/t2)/ln(l1/l2). The A-product serves as a backup for the M-product, and is helpful to place the 20+ year heritage AVHRR aerosol record in context of the more accurate M-aerosols, and to quantify the MODIS multi-channel improvements. This study documents the M- and A-products, highlighting their CERES SSF specifics, and preliminarily inter-compares them using two weeks of global Terra data. When both products are available, tA strongly correlate with tM in both bands. The a-comparison is noisier at low t but progressively improves as t increases. However, the domains in which the M- and A-aerosols are available, and respective t/a statistics, differ. The major cause for the differences in the products is different sampling (i.e. cloud and glint screening). In both M- and A-products, correlation is observed between the retrieved aerosol parameters (t/a), and ambient cloud amount. Similar correlation was previously noticed in the AVHRR retrievals. More studies are needed to better understand the two products, and realize their potential more fully.
Poster Session 6, Climatology and Long-Term Studies
Wednesday, 22 September 2004, 2:30 PM-4:30 PM
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