Satellite-observed relationships between aerosol and trade-wind cumulus cloud properties over the Indian Ocean



[1] We examine the relationships between simultaneous observations of aerosol properties from the Multiangle Imaging SpectroRadiometer (MISR) and trade-wind cumulus macrophysical properties including cloud fraction (fc), cloud size and cloud top height (hct) distribution from the Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) over the Indian Ocean during the dry season (Nov–Apr) of 2006–2007. Mean fc increases from 0.029 to 0.089 with an increase in aerosol optical depth (τa) from 0.1 to 0.3, plateaus between 0.3 < τa < 0.45 and decreases by >30% at τa > 0.45. The hct displays insensitive response to increasing τa for τa < 0.4, but reduces at τa > 0.4. Cloud size distribution shifts significantly to large cloud size at τa > 0.45, possibly due to more efficient desiccation of small clouds under semi-direct effect. The observed changes in cloud properties in relation to increasing τa suggest a very complex interaction between trade-wind cumuli and absorbing aerosols that cannot be explained by potential remote sensing artifacts or synoptic meteorology. Further examination of the potential role of mesoscale meteorology on such relationships using multi-year data sets is warranted.