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

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.

Automated summary

Using the ICON-S model, we are able to effectively describe the seasonal and diurnal features of the tropical rainbelt. The model performs well over land and shows high agreement with observations. However, it struggles to capture the seasonal features of the rainbelt over the oceans in the Eastern Hemisphere, which is associated with a cold sea surface temperature bias.