The dependence of vertical cloud profiles from CloudSat-CALIPSO retrievals on the degree of convective aggregation

Friday, 19 December 2014
Christopher E Holloway, University of Reading, NCAS-Climate, Meteorology, Reading, RG6, United Kingdom, Thorwald Stein, University of Reading, Meteorology, Reading, United Kingdom, Isabelle Tobin, Institut Pierre Simon Laplace, Laboratoire des Sciences du Climat et de l’Environnement, Paris, France and Sandrine Bony, Laboratoire de Météorologie Dynamique UPMC, Paris, France
Previous work (Tobin et al. 2012, Tobin et al. 2013) has found that the degree of aggregation of convection in satellite observations, as measured by the Simple Convective Aggregation Index (SCAI), is associated with systematic differences in mean environmental moisture and outgoing longwave radiation for a given large-scale forcing. This suggests that climate models need to simulate the degree of organization of convection, and not just the mean precipitation and convective fluxes, in order to fully represent interactions between convection and larger scales. In this study, we use five years of CloudSat-CALIPSO cloud profiles alongside TRMM rainfall, geostationary IR data, ERA-Interim water vapor, and other observations to investigate the relationship between vertical cloud distributions and the SCAI aggregation index. We find that there is a significant decrease in anvil cloud (and in cloudiness as a whole) and increase in shallow cumulus as aggregation increases (for a given precipitation rate). There are also greater variations in most cloud fractions and types when varying SCAI for a given precipitation than when varying precipitation for a given SCAI.