Learning by Doing: Seasonal and Diurnal Features of Tropical Precipitation in a Global-Coupled Storm-Resolving Model

Abstract

Using the global and coupled ICOsahedral Nonhydrostatic model with the Sapphire configuration (ICON-S) and a grid spacing of 5 km, we describe seasonal and diurnal features of the tropical rainbelt and assess the limits of ICON-S in representing tropical precipitation. ICON-S shows that, by resolving meso-beta scale process, the rainbelt structure and its seasonality (zonal and meridional migration and enlargement) is reproduced, with better performance over land than over ocean and with a very high degree of agreement to observations. ICON-S especially struggles in capturing the seasonal features of the tropical rainbelt over the oceans of the Eastern Hemisphere, an issue associated with a cold sea surface temperature (SST) bias at the equator. ICON-S also shows that a perfect representation of the diurnal cycle of precipitation over land is not a requirement to capture the seasonal features of the rainbelt over land, while over the ocean, 5 km is sufficient to adequately represent the diurnal cycle of precipitation.