Cloud Macro- and Microphysical Characterization Using ASTER High-Resolution Satellite Data Combined with Aircraft in-Situ Data from ACTIVATE

The Aerosol Cloud meTeorology Interactions oVer the western ATlantic Experiment (ACTIVATE) implemented a twin-aircraft field sampling strategy to comprehensively characterize clouds, aerosols, and meteorological conditions along the western North Atlantic Ocean. A lower-altitude aircraft collected boundary layer in-situ measurements while concurrently, a higher-altitude aircraft gathered lidar and polarimeter measurements of the boundary-layer clouds and aerosols below the plane, along with dropsonde atmospheric profiles. ACTIVATE's research aircrafts sampled six specifically-chosen ASTER tracks, each encompassing a latitudinal range of 1 to 2 degrees. In combination these measurements provide a unique opportunity to understand satellite cloud characterization at spatial scales smaller than those of conventional satellites and assess potential retrieval artifacts. The cloud types encountered varied from sparse, thin cumulus to stratiform. Cloud sizes are computed from a cloud mask imposed upon the 15-m resolution ASTER radiances, and combined with Research Scanning Polarimeter (RSP) retrievals of cloud optical depth and effective radius, which are insensitive to three-dimensional radiative transfer effects, and in-situ cloud microphysical measurements. The RSP-derived effective radii are consistent with in-situ FCDP measurements. A comparison between cloud size computed from ASTER radiances and Terra MODIS indicate a significant proportion of clouds were smaller than the 1-km pixel resolution of MODIS. MODIS tends to overlook thinner clouds while underestimating the cloud optical depth for thicker clouds when compared to values derived from RSP. A consistent overestimate of the droplet effective radius by MODIS ultimately propagates into an underestimation in the MODIS-derived droplet concentration (Nd). Initial assessments unveil a consistent increase in cloud optical thickness for larger cloud sizes, while the droplet effective radii remains constant. A comprehensive evaluation of all six cases will be presented, addressing the potential impact of environmental mixing through cloud-sides and cloud-top entrainment.