The Effect of Convective Response Time on WISHE Modes

Abstract

Recent research has shown that a variety of wavelike oscillations in the tropics may be explained by instabilities driven by wind-induced surface heat exchange (WISHE). All such studies to date have implicitly assumed that moist convection is in quasi equilibrium with the flow in question. Here that assumption is relaxed by accounting for a small but nonzero lag between the large-scale forcing of convection and its response. Reaction times as short as 30 minutes damp the higher-frequency Kelvin-like equatorial modes, favoring zonal wavenumbers 1?4, and strongly bias the higher-order modes to westward-propagating disturbances of synoptic scale. An analysis of off-equatorial disturbances reveals a preference for poleward- and westward-propagating modes with wavelengths of the order of 1000 km.