An Imager Remote Sensing Technique for Simultaneous Retrievals of Above-Cloud Absorbing Aerosols and Underlying Boundary Layer Stratocumulus Clouds (Invited Presentation)

The characterization of clouds, aerosols, and their interactions continues to be a key contributor to the uncertainty in our current understanding of the Earth’s atmosphere and radiation budget. Of particular interest here are the absorbing aerosols prevalent over the southeast Atlantic Ocean during austral winter, largely originating from biomass burning activities in the southern African savanna, that often overly quasi-permanent marine boundary layer stratocumulus clouds. Global models generally disagree on the regional radiative effect of these SE Atlantic absorbing aerosols, with some suggesting a regional warming effect and others cooling. Because of the disparate direct radiative effects (DRE) of absorbing aerosols in clear sky (cooling effect) or above clouds (warming effect), this disagreement arises in part from inter-model differences in the representation of not only the aerosol layer itself, but the cloud layer as well. It is therefore important to place observational constraints on the characterization of the aerosol and cloud layers, as well as the regional aerosol DRE. To this end, a new imager remote sensing technique has been developed to simultaneously retrieve above-cloud absorbing aerosol optical thickness (AOT) and the optical thickness (COT) and effective droplet radius (CER) of the underlying boundary layer clouds, key radiative quantities necessary for observational estimates of aerosol DRE. The retrieval technique uses reflectance observations in multiple spectral channels in the visible and near- and shortwave-infrared, and can be applied to observations from any imaging remote sensor that provides similar spectral coverage. Here, results are shown from the Moderate-resolution Imaging Spectroradiometer (MODIS) onboard NASA’s Terra and Aqua satellites.