Rains and Showers in OTREC; Weak Temperature Gradient Modeling

Abstract

Abstract Rainfall in the tropics has been shown to be produced either by isolated but intense convective systems (showers regime) or widespread but weaker systems (rains regime). We examine significant rainfall systems observed in the OTREC project (Organization of Tropical East Pacific Convection) in order to tease out the physical mechanisms differentiating these two regimes. We find that rains occur in very moist environments, typically with weak conditional instability. In contrast, showers develop in drier environments with larger instability. Spectral weak temperature gradient numerical calculations show that showers are associated with episodic rainfall separated by significant quiescent periods, whereas rains produce continuous simulated rainfall after a spinup period. Mass flux profiles of showers and rains are very different, resulting in different effects on the large scale environment.