Improved Performance of High-Resolution Climate Models in Simulating Asian Monsoon Rainfall Extremes

Abstract

Rainfall extremes are one of the most difficult features to simulate using global climate models. Using pairs of high- and low-resolution atmosphere-only simulations from the High-Resolution Model Intercomparison Project, we assess whether and how the horizontal grid spacing influences model's skill in simulating the Asian summer monsoon rainfall extremes. Despite the large inter-model spread, improved model performance is seen across most models as resolution increases, both in terms of spatial distribution and intensity of monsoon rainfall extremes. Rainfall extremes are enhanced at the windward side of steep topography such as the foothills of Himalayas, and in the heavy monsoon regions such as central India, southern China, and western North Pacific. The improvements are found to be associated with a better representation of the vertical ascents and models' ability in simulating the rain-producing synoptic low-pressure systems, which are more frequent and stronger at higher resolutions.