Exploring cloud fraction adjustments in the South Pacific marine stratocumulus cloud deck using 3 years of GOES 16 retrievals

Marine stratocumulus clouds contribute a significant cooling effect to the Earth's climate, but their role in global climate change hasn't been well quantified. Aerosols from anthropogenic and natural sources alter the characteristics of stratocumulus clouds, although the extend of all cloud adjustments is not yet fully quantified. In particular the cloud fraction adjustment is associated with potentially large radiative forcings, but also high uncertainties. We used cloud retrievals from the GOES-East satellite to explore cloud fraction adjustments in raining stratocumuli structures, and MERRA-2 aerosol reanalysis data as a proxy for the aerosol-dependent cloud droplet size. We found that increases in aerosol loading coincide with both increases and decreases in cloud fraction relative to the climatological mean. Decreases in aerosol loading coincide with increases in the fraction of optically thin cloud features which were calculated for various maximum thresholds of optical depth. For cloud covers with cloud fractions and optically thin cloud areas close to the climatological mean, increased aerosol loading tends to coincide with increases in both of these properties. This is not the case for cloud covers that differ significantly from the climatological mean. A better understanding of the link between how cloud fraction and optical density respond to aerosol loading could help to improve our knowledge of the effects of aerosols on the radiative properties of stratocumuli.