Development of a cumulus parameterization suitable for use in mesoscale through GCM-scale models
Date
1996-06-11
Authors
Rafkin, Scot C. R., author
Journal Title
Journal ISSN
Volume Title
Abstract
A cumulus parameterization is described and implemented into the Regional Atmospheric Modelling System (RAMS). Although specifically formulated for use in mesoscale model applications, it can be applied with equal validity in larger-scale models. The new cumulus parameterization is a hybrid mass flux and adjustment scheme. The mass flux component closely follows the theory developed in the Arakawa-Schubert parameterization to describe the change in the cloud environment due to cumulus induced subsidence and detrainment. However, the cloud-base mass flux is computed using a prognostic cumulus kinetic energy equation. The adjustment component describes the change in the grid average property due to the expansion or contraction of cloud area. Unlike most adjustment schemes, the adjustment time scale is not the lifetime of convection, but the growth rate of convective area. Therefore, the adjustment term can either nudge the grid average property toward the cloud profile or toward the environment value. The major benefit of this parameterization is that it is designed to be valid over scales ranging from meso-1 (5 km) to GCM scale (200 km) grid spacings. Comparison of explicitly simulated convection at a horizontal grid resolution of 1.5 km with parameterized simulations at 20 km, 12 km and 6 km are made. Comparisons to the Kuo parameterization are also discussed. Results indicate that the new parameterization does a good job at reproducing the effects of convection as simulated in the cloud resolving simulations, and performs immensely better than the Kuo parameterization.
Description
June 11, 1996.
Also issued as author's dissertation (Ph.D.) -- Colorado State University, 1996.
Also issued as author's dissertation (Ph.D.) -- Colorado State University, 1996.
Rights Access
Subject
Convection (Meteorology)
Cumulus
Cloud physics