HR: 1340h
AN: A23C-0810    [Abstracts]
TI: Monte Carlo Approach to Estimating the Global Anthropogenic Aerosol Forcing: Sensitivity to Assumptions and Datasets
AU: * Chung, C E
EM: cchung@fiji.ucsd.edu
AF: Scripps Institution of Oceanography, Mail code: 0221, La Jolla, CA 92093 United States
AU: Podgorny, I
EM: igor@fiji.ucsd.edu
AF: Scripps Institution of Oceanography, Mail code: 0221, La Jolla, CA 92093 United States
AU: Ramanathan, V
EM: ram@fiji.ucsd.edu
AF: Scripps Institution of Oceanography, Mail code: 0221, La Jolla, CA 92093 United States
AB: A preliminary estimate of the direct effects of the anthropogenic aerosols on the solar radiation is made. The approach is to use our Monte-Carlo Aerosol-Cloud Radiation (MACR) model to generate the global monthly climatology of the aerosol forcing at its recent level, say from 1995-2003. An earlier version of the MACR was developed and validated during INDOEX, and was updated for this study to include Monte Carlo integration of atmospheric fluxes in multidimensional parameter space. Additional update features include a) making the model global, b) using observed global ozone, precipitable water and surface albedo, c) accounting for the effect of the surface orography, and d) using observed cloud information from ISCCP D2. GOCART, MODIS and AERONET products were processed to obtain AOD, SSA and asymmetry parameter as inputs for the MACR. The global mean forcing in cloudy skies is -0.75 Wm-2 at the TOA, 3.0 Wm-2 in the atmosphere and -3.75 Wm-2 at the surface. The NH mean is -0.92 Wm-2 (TOA), 3.85 Wm-2 (atmosphere) and -4.76 Wm-2 (surface), and the SH mean -0.58 Wm-2 (TOA), 2.15 Wm-2 (atmosphere) and -2.73 Wm-2 (surface). These estimates are based upon certain assumptions and certain combination of the datasets. In case we use AOD, SSA and asymmetry parameter derived without AERONET, the forcing is -0.58 Wm-2 (TOA), 3.35 Wm-2 (atmosphere) and -3.93 Wm-2 (surface). We present various estimates by changing the assumption of aerosol mixing, making the sky clear, or changing the aerosol vertical profile.
DE: 3309 Climatology (1620)
DE: 1610 Atmosphere (0315, 0325)
DE: 0305 Aerosols and particles (0345, 4801)
SC: Atmospheric Sciences [A]
MN: 2004 AGU Fall Meeting