HR: 09:36h
AN: A21E-08    [Abstracts]
TI: Aerosol direct radiative forcing over oceans from merged MODIS/CERES analysis
AU: * Zhang, J
EM: zhang@nrlmry.navy.mil
AF: NRL / UCAR, Naval Research Laboratory, Monterey, CA 93943
AU: Christopher, S A
EM: sundar@nsstc.uah.edu
AF: Department of Atmospheric Science, University of Alabama in Huntsville, 320 Sparkman Dr., Huntsville, AL 35805
AU: Remer, L A
EM: lorraine.a.remer@nasa.gov
AF: NASA / GSFC, code 913, Greenbelt, MD 20771
AU: Kaufman, Y J
EM: yoram.j.kaufman@nasa.gov
AF: NASA / GSFC, code 913, Greenbelt, MD 20771
AB: Using 10 months of Single Scanner Footprint (SSF) data that combines the multi-spectral Moderate Resolution Imaging Spectroradiometer (MODIS) cloud and aerosol products with the Clouds and the Earth's Radiant Energy System (CERES) Top-of-Atmosphere (TOA) broadband shortwave and longwave fluxes, we provided the observational estimates of the instantaneous cloud-free shortwave aerosol radiative forcing (SWARF) over the global oceans. Different from our previous research, we corrected for both the sample biases and the diurnal cycle of SWARF. We also accounted for the variation in the CERES TOA radiation fields due to changes in aerosol optical properties by using aerosol Angular Distribution Models that are constructed as functions of MODIS aerosol optical depth, the ratio of small mode to total aerosol optical depth, and Special Sensor Microwave Imager (SSM/I) wind speed. We estimated the instantaneous TOA SWARF from Terra overpass time to be -6.4 +- 2.6 Wm-2, and is -5.3 +- 1.7 Wm-2 over cloud-free oceans after accounting for the sample bias and diurnal averaging. Our study is a measurement-based assessment of cloud-free aerosol radiative forcing and could be used as a validation tool for numerical modeling studies.
DE: 3359 Radiative processes
DE: 3360 Remote sensing
DE: 4801 Aerosols (0305)
DE: 0305 Aerosols and particles (0345, 4801)
SC: Atmospheric Sciences [A]
MN: 2004 AGU Fall Meeting