Characteristics of Cumulus Population, Microphysical and Radiative Properties Observed over Southeast Atlantic

Tropical marine boundary layer clouds have a large effect on Earth’s energy budget and are known to be the regime where climate models disagree substantially in the magnitude of cloud feedback. In particular, the representation of cloud processes and interactions with aerosol and radiation in shallow cumulus regime is challenging, because of their subgrid size and small cloud cover and because the cloud field is highly heterogeneous. To improve the representativeness of cloud simulations and to evaluate the accuracy of convective scheme, detailed observations in clouds are crucial for quantifying their variability across scales and atmospheric conditions and for evaluating their physical relationships with aerosols and dynamics. In this study, we will characterize cumulus population and properties using about 300 three-dimensional (3D) cumulus fields observed from the Layered Atlantic Smoke Interactions with Clouds (LASIC) campaign at Ascension Island during July–September 2017. These fields are retrieved at high spatial resolution and are accounted for 3D radiative effects, capitalizing on an ensemble optimization approach and synergistic measurements of scanning cloud radar, lidar and shortwave spectrometer. Since it is for the first time, that so many 3D cloud fields were constructed directly from observations, rather than derived from 1D or 2D statistics, we will highlight the differences between 1D soda-straw view and 3D in cloud properties and radiative statistics. Importantly, we will show the co-variability between cloud population, geometry, microphysics and atmospheric conditions to better understand what triggers cumulus clustering and precipitation onset.