Why does cloud superparameterization improve the simulated daily rainfall cycle in a multiscale climate modeling framework?
Michael S. Pritchard, SIO/Univ. Of California, La Jolla, CA; and R. C. J. Somerville The Multiscale Modeling Framework (MMF*) approach to global climate modeling results in improved simulations of small-scale, fast (daily) rainfall variability, but understanding why is difficult. Analysis of the vertically integrated diurnal composite moisture budget provides several new clues to the physical processes involved. Daytime entrainment humidification resolved by the embedded cloud-resolving model (CRM) in the Super-Parameterized Community Atmosphere Model v3.0 (SPCAM3) tempers the amplitude and fixes the timing of the overly vigorous CAM3 diurnal rainfall cycle over land. Diurnal water budget analysis shows that at night time, and over the ocean, substantially different representations of diurnal moisture convergence in the two models play a major role in differentiating daily tropical rainfall. In CAM3 a large-scale equatorial planetary wave of diurnal moisture convergence and storage con
