The Dependence on Convection Parameterization of the Tropical Intraseasonal Oscillation Simulated by the UIUC 11-Layer Atmospheric GCM

Abstract

Abstract Numerical experiments are conducted using the University of Illinois, Urbana–Champaign (UIUC), 11-layer atmospheric general circulation model (GCM) to investigate the dependence of the simulated tropical intraseasonal oscillation (TIO) on convection parameterization. Three convection parameterizations have been tested: 1) the UIUC GCM’s original cumulus–convection parameterization, which includes a modified version of the Arakawa–Schubert penetrative–convection parameterization and a middle-level convection parameterization, 2) the parameterization of Kuo, and (3) the moist convective adjustment parameterization of Manabe et al For each parameterization a relative humidity criterion (RHc) for convection or convective heating to occur is used, as in many GCMs. Perpetual-March simulations with these convection parameterizations have been performed for different values of RHc. It is found that the simulated TIO is highly dependent on RHc. As RHc increases, the oscillation in the simulations becomes ...