Gravity Waves and the Diurnal Cycle of Precipitation in the Maritime Continent Region

Convection in the maritime continent is comprised of multi-scale coherent structures ranging from the Madden-Julian Oscillation (MJO) down to land and sea breezes initiated along complex coastlines. In the maritime continent the diurnal cycle is a prominent feature of the convective cloud and precipitation distributions. In addition to the afternoon or evening peak in convective activity over land, many maritime continent regions have a secondary nocturnal or early-morning precipitation maximum located over the ocean. This secondary maximum can be linked to land breeze circulations and offshore propagating gravity waves. However, many aspects of the dynamics of these processes and their regional variation are poorly understood. In this study we use large-domain convection-permitting model simulations over the maritime continent to better understand the processes that control the diurnal cycle, especially in offshore precipitation. In particular, we demonstrate the influence of the offshore propagating gravity waves on: 1) organized convection near the coast; and 2) modulation of precipitation further offshore. We present specific examples during January – February 2010, focusing on the New Guinea region in particular, and examine the variation of the dominant processes during different phases of the MJO.