Examination of direct cumulus contamination on MISR-retrieved aerosol optical depth and angstrom coefficient over ocean

The effect of direct cumulus contamination on the aerosol optical depth (AOD) and angstrom exponent (AE) from the Multi-angle Imaging SpectroRadiometer (MISR) was examined using overlapped 15-m resolution data from the Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) over the tropical western Atlantic Ocean (RICO), the Gulf of Mexico (GOMX), and Indian Ocean (INDI). Overall, 12%, 6% and 11% of MISR 1.1-km pixels for aerosol retrievals contain some clouds, but 97%, 100% and 89% of these MISR pixels have the clouds covering less than 5% of the MISR pixel area over RICO, GOMX and INDI, respectively. On average, cumuluscontaminated pixels increase AOD at 558 nm by 0.02, 0.02 and 0.00 and decrease AE by 0.03, 0.11 and 0.04 for RICO, GOMX and INDI, respectively. Based on these findings, a MISR-derived aerosol optical depth climatology over the tropical oceans is biased high by no more than 0.002 from direct cumulus contamination.