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Aerosol Direct Forcing at TOA and Surface for Clear and Cloudy Conditions

Charlock, T.P.(a), Rose, F.G.(b), Rutan, D.A.(b), Fillmore, D.(c), and Collins, W.(c), NASA Langley Research Center (a), Analytical Services and Materials, Inc. (b), National Center for Atmospheric Research (c)
Fourteenth Atmospheric Radiation Measurement (ARM) Science Team Meeting

Direct aerosol forcing can be affected dramatically by cloudiness. For example, with a continental AOT of 0.25 and soot AOT of 0.05 at scale height 2km over the tropical ocean with cosSZA of 0.33, the computed forcing to SW reflection at TOA is 15 Wm-2. If we include a boundary layer cloud with a top at 1km and an optical depth 20, the same TOA forcing then reverses sign and becomes -22 Wm-2. A new CERES Terra Surface and Atmosphere Radiation Budget (SARB) provides as assessment of direct aerosol forcing in all sky, as well as cloud free, conditions; at surface and TOA for both LW and SW. Fluxes are computed with a Fu-Liou code using NWP profiles, MODIS cloud retrievals, and aerosol optical properties from the MATCH assimilation; these are compared operationally with CERES broadband TOA observations (for every footprint) and with surface observations (at over 40 sites, including ARM). Forcing is assessed by a second set of calculations with no aerosols. A companion poster by Rutan shows how the MODIS aerosol retrievals over land reduce the error in Terra SARB surface insolation more than factor of two, versus 1998 TRMM SARB in the EOS archive. The most advanced form of the Terra SARB has been processed for only a single orbit. It shows clouds forcing an enhancement of SW absorption within the atmosphere by dust (Tegen and Lacis) and soot (OPAC) over regions of Central Asia and East Africa. Such in-atmosphere forcing affects the hydrological cycle, as well as the TOA budget. The poster will display the results of several months of such in-atmosphere, all-sky aerosol forcing and contrast it with the more traditional clear sky TOA aerosol forcing released earlier.

Note: This is the poster abstract presented at the meeting; an extended version was not provided by the author(s).