Estimation of direct aerosol solar radiative forcing from MOS-B measurements

Aerosol retrieval over the ocean is a major task for present and future satellite missions. With nadir looking sensors no information about absorption by aerosol can be obtained. Absorbing aerosols lead to the estimation of too low an aerosol optical depth. The climatic effect of aerosols in the solar spectral region can be expressed by the change of integrated upward radiative flux (URF) at the top of the atmosphere due to the presence of aerosols. Usually URF is derived from remotely sensed aerosol parameters using a radiative transfer model. The errors in the aerosol parameters are propagated to the URF. In this paper a method is presented deriving the URF directly from measured radiances. Aerosol absorption does not affect this retrieval method. The retrieval algorithm is based on a regression scheme. Regression parameters are derived from radiative transfer simulations. Sensitivity tests are performed in order to estimate the influence of sensor noise and change of sea surface roughness on the algorithm. The retrieval is applied to Modular Optoelectronic Scanner scenes of the North Sea and the North Atlantic