Future changes in spatiotemporal precipitation patterns of the East Asian summer monsoon and associated uncertainty factors

Abstract. East Asia has been identified as a key area at risk of precipitation increases resulting from global warming. East Asian summer monsoon has distinct spatiotemporal characteristics and the simulation characteristics of global climate models therefore needs to be evaluated closely to obtain a reliable projection of future precipitation patterns and associated extreme events. Using metrics for the spatiotemporal variability of monsoon precipitation over East Asia, this study evaluated the performance of Coupled Model Intercomparison Project Phase 6 (CMIP6) models and analyzed future projections and uncertainty factors. Spatiotemporal precipitation patterns were simulated reasonably well by CMIP6 models but with weaker rainfall amplitudes. CMIP6 models simulated more intense precipitation than the predecessor CMIP5 ones and captured observations better. In future projections, an overall precipitation increase occurs during both the northward migration of the rain band and during peak monsoon time over East Asia and the three subregions, with stronger changes under higher emission scenarios. This increase was mainly ascribed to a thermodynamic response due to increased moisture availability. Internal climate variability and model uncertainty dominated future precipitation uncertainties. Dynamic terms explained a large portion of model uncertainty due to circulation changes, and thermodynamic terms were significantly related to scenario uncertainty.