Joint Seminar: Global-coupled storm-resolving model: a tool to better understand tropical precipitation

In this study, we use the one-year simulation of the global-coupled ICON model with the Sapphire (ICON-S) configuration integrated with a grid spacing of 5 km to analyze the impact of resolving meso-beta scale processes on tropical precipitation. The zonal as well as meridional seasonal migration of the terrestrial rainbelt, both in terms of area and location, are represented in ICON-S with excellent agreement to observations. This result remains true, eventhough ICON-S simulates a more intense and two-hour earlier peak in precipitation, suggesting that details of the diurnal cycle does not affect the monthly mean properties of the terrestrial rainbelt. The seasonality of oceanic rainbelts is also well represented in the Eastern Pacific and Atlantic. This is not the case in the Indo-Pacific region, where ICON-S struggles to simulate the sea surface temperature pattern, distorting the representation of the tropical rainbelt in this region.
With this analysis, we show that the improvements in the representation of precipitation shown on regional continental domains using storm-resolving models are, indeed, because of resolving meso-beta scale processes and not due to the prescribed large-scale circulation in such models. The extraordinary performance of ICON-S over land, even with ocean biases, suggests a mechanism not present in the ocean that makes precipitation over land so robust. The small interannual variability of the summer precipitation area over land in observations, in contrast to ocean, also points to the existence of such a mechanism.




13:30 h


Bundesstr. 53, room 022/023
Seminar Room 022/023, Ground Floor, Bundesstrasse 53, 20146 Hamburg, Hamburg


Hans Segura


Swantje Bastin

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