HR: 0800h
AN: A11C-0064    [Abstracts]
TI: Aerosol Direct Radiative Forcing Climatology Based on AERONET Measurements
AU: * Zhou, M
EM: mzhou@eas.gatech.edu
AF: School of Earth and Atmospheric Sciences, Georgia Institute of Technology, 311 Ferst Drive, Atlanta, GA 30332
AU: Yu, H
EM: hongbin.yu@eas.gatech.edu
AF: School of Earth and Atmospheric Sciences, Georgia Institute of Technology, 311 Ferst Drive, Atlanta, GA 30332
AU: Kaufman, Y
EM: yoram.j.kaufman@nasa.gov
AF: Laboratory for Atmospheres, NASA Goddard Space Flight Center, Greenbelt, MD 20771
AU: Chin, M
EM: chin@rondo.gsfc.nasa.gov
AF: Laboratory for Atmospheres, NASA Goddard Space Flight Center, Greenbelt, MD 20771
AU: Dickinson, R
EM: robted@eas.gatech.edu
AF: School of Earth and Atmospheric Sciences, Georgia Institute of Technology, 311 Ferst Drive, Atlanta, GA 30332
AU: Remer, L
EM: remer@crb02.gsfc.nasa.gov
AF: Laboratory for Atmospheres, NASA Goddard Space Flight Center, Greenbelt, MD 20771
AU: Dubovik, O
EM: dubovik@ltpmail.gsfc.nasa.gov
AF: Laboratory for Atmospheres, NASA Goddard Space Flight Center, Greenbelt, MD 20771
AB: AEosol RObotic NETwork (AERONET) is a sunphotometer network covering virtually all aerosol regimes around the world. It measures and derives spectral aerosol optical depth, single-scattering albedo, phase function/asymmetry factor for both fine-mode and coarse-mode aerosols and for up to 10 years. These high quality data can be used to derive measurement-based aerosol direct forcing climatology that will serve as a baseline for evaluating the satellite-based and model-based forcing assessment. In this study, the aerosol climatology, in conjunction with surface albedo and cloud products from MODIS, is used to calculate the aerosol direct forcing/forcing efficiency (forcing per unit optical depth at 550nm) under cloud-free and cloudy conditions, for total and fine-mode aerosols, and at the top-of-atmosphere (TOA) and the surface. For biomass burning aerosols, we find that the average forcing efficiency over South America is smaller by ~30% at the TOA but larger by ~35% at the surface than that over South Africa, because of stronger absorption by the South Africa smoke. For mineral dust, the surface albedo is another important factor that determines aerosol forcing. We find that, over Saharan deserts, Arabian Peninsula, and their surrounding oceans, the surface albedo ranges from ~0.1 to ~0.35. The dust forcing efficiency substantially decreases at the TOA from -44 to -17 W/m2 and at the surface from -80 to -48 W/m2 with increasing surface albedo. We also find that the forcing efficiency of fine-mode aerosol is larger at the TOA while smaller at the surface than that of total aerosol, which is mainly determined by a larger single-scattering albedo and smaller asymmetry factor of fine-mode aerosol. Cloudy-sky aerosol direct forcing is usually not negligible for the observed cloud optical thickness and is sensitive to the relative location of aerosol and cloud layer.
DE: 3359 Radiative processes
DE: 1620 Climate dynamics (3309)
DE: 0305 Aerosols and particles (0345, 4801)
SC: Atmospheric Sciences [A]
MN: 2004 AGU Fall Meeting