| Summary: | The Geostationary Earth Radiation Budget (GERB) instruments flying on the Meteosat Second Generation series of satellites provide a unique tool with which to monitor the diurnally resolved evolution of the top of atmosphere broad-band radiation fields. Edition 1 GERB climate quality products have recently been released to the scientific community, and, in addition to the observed radiances and inferred fluxes, also include information concerning the aerosol field sampled by the instrument. However, as yet, no dedicated scheme to account for the anisotropic characteristics of aerosol has been incorporated in the short-wave radiance to flux conversion methodology, which instead uses anisotropic factors from angular distribution models developed for clear or cloudy conditions. Here we attempt to quantify the impact of this omission, focussing specifically on the North Atlantic Ocean (10-30°N, 10-60°W) through spring 2006. Using Edition 1 GERB fluxes as they stand, the three month regional mean TOA instantaneous short-wave aerosol direct radiative effect efficiency in cloud-free conditions is ~86 W m-2 per unit aerosol optical depth. Accounting for the effect of aerosol on the anisotropy of a given scene reduces this value to ~75 W m-2 per unit aerosol optical depth, a value which shows greater consistency with previous estimates made using observations from instruments in polar orbit. 1.
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