All-sky direct aerosol radiative effects estimated from integrated A-Train satellite measurements

Abstract

The improvement of satellite-derived calculations of direct aerosol radiative effects (DARE) is essential for reducing the uncertainty in the impact of aerosol on solar radiation. We develop a framework to compute DARE at the top of the Earth's atmosphere, in the shortwave part of the electromagnetic spectrum, and in all-sky conditions along the track of the A-Train constellation of satellites. We use combined state-of-the-art aerosol and cloud properties from the Cloud-Aerosol Lidar with Orthogonal Polarization (CALIOP) and the Moderate Resolution Imaging Spectroradiometer (MODIS) satellite sensors. We also use a global reanalysis from the Modern-Era Retrospective Analysis for Research and Applications version 2 (MERRA-2) to provide vertical distribution of aerosol properties and atmospheric conditions. Diurnal mean satellite DARE values range from -25 W m-2 (cooling) to 40 W m-2 (warming) over the southeast Atlantic during 3 days from the NASA ObseRvations of Aerosols above CLouds and their intEractionS (ORACLES) aircraft campaign. These 3 days indicate agreement between our satellite-calculated DARE and co-located airborne Solar Spectral Flux Radiometer (SSFR) measurements. This paper constitutes the first step before applying our algorithm to more years of combined satellite and model data over more regions of the world. The goal is to ultimately assess the order of importance of atmospheric parameters in the calculation of DARE for specific aerosol and cloud regimes. This will inform future missions about where, when, and how accurately the retrievals should be performed to reduce all-sky DARE uncertainties.