Extended Abstract (2.0M)P1.1
Top-of-Atmosphere Direct Radiative Effect of Aerosols from the Clouds and the Earth's Radiant Energy System (CERES) Satellite Instrument Over the Tropical Oceans
Norman G. Loeb, Hampton University, Hampton, VA; and S. Kato
Nine months of broadband radiative fluxes from the Clouds and the Earth's Radiant Energy System (CERES) satellite instrument aboard the Tropical Rainfall Measuring Mission (TRMM) spacecraft are combined with coincident high-resolution Visible Infrared Scanner (VIRS) measurements to estimate the daily average direct radiative effect of aerosols over the tropical oceans. On average, aerosols have a cooling effect of 4.6 W m-2 over the tropics. The magnitude is approximately 2 W m-2 smaller over the southern tropical oceans than it is over northern tropical oceans. The direct effect derived from CERES is highly correlated with coincident aerosol optical depth retrievals inferred from 0.63 µm VIRS radiances (correlation coefficient of 0.96). The slope of the regression line is approximately -32 W m-2 t-1 over the equatorial Pacific Ocean, but changes both regionally and seasonally, depending on the aerosol characteristics. Near sources of biomass burning and desert dust, the aerosol direct effect reaches -25 W m-2 to -30 W m-2. The direct effect from CERES also shows a dependence on wind speed. The reason for this dependence is unclear-it may be due to increased aerosol (e.g. sea-salt or aerosol transport) or increased surface reflection (e.g. due to whitecaps). The uncertainty in the tropical average direct effect from CERES is 1 W m-2 (20%) due mainly to cloud contamination, the radiance-to-flux conversion, and instrument calibration. By comparison, uncertainties in the direct effect from the ERBE and CERES "ERBE-Like" products are a factor of 3 to 5 larger.
Poster Session 1, Radiative Forcing and Remote Sensing of Aerosols (Parallel with Joint Poster Session JP1)
Monday, 3 June 2002, 1:00 PM-3:00 PM
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