Capability Assessment of CMIP5 Models in Reproducing Observed Climatology and Decadal Changes in Summer Rainfall with Different Intensities over Eastern China

The capabilities of 17 CMIP5 models for simulating the intensity distribution of summer rainfall over eastern China are evaluated based on daily observational data. The decadal changes of rainfall with different intensities in the later 1970s and their relative contributions to the decadal change in total rainfall for both observation and model simulations are further analyzed and compared. Observations indicate that the total rainfall is mainly composed of light and medium rainfall over northern and northeastern China, while heavy rainfall account for a large proportion of the total rainfall over southern China and the Yangtze-Huai River basin (YHRB). In general, the CMIP5 models are able to capture the observed spatial distribution of proportion of light and heavy rainfall to total rainfall amount in Eastern China, except for medium rainfall. Most models have a bias toward an overestimation of the light and medium rainfall events, and an underestimation of heavy rainfall events. Therefore, these models overestimate the amount of total rainfall over northern and northeastern China and underestimate the amount of total rainfall over southern China and the YHRB. Our analysis indicates that the observed decadal changes in total rainfall over northern China and the YHRB in the late 1970s are mainly attributed to changes in heavy rainfall events. Over northern China, a few CMIP5 models reproduced the observed decadal decrease in both heavy rainfall and total rainfall. Over the YHRB, several models can reproduce the observed decadal increase in total rainfall. However, these models failed to reproduce the increase in heavy rainfall amount due to the model bias of a severe underestimation of heavy rainfall. The authors also find out that multi-model ensemble technique cannot significantly improve the model performance in simulating the spatial distribution of rainfall intensity, especially its decadal changes.