Evaluation of the precipitation seasonal variation over eastern China simulated by BCC_CSM model with two horizontal resolutions

Abstract

AbstractThe performance of Beijing Climate Center climate system model (BCC_CSM) with two horizontal resolutions in simulating the precipitation seasonal variation over eastern China has been evaluated. The possible reasons related to the differences in the simulations of BCC_CSM1.1 m model with fine resolution and BCC_CSM1.1 model with coarse resolution also have been addressed and discussed. Results show that the improved simulation of the timing and amount of precipitation in dry seasons except for larger biases during rainy seasons can be noted in BCC_CSM1.1 m model relative to BCC_CSM1.1 model. The occurrence time of the precipitation annual peaks in BCC_CSM1.1 m model shows better agreements with the observation compared to BCC_CSM1.1 model. Mechanism analysis indicates that BCC_CSM1.1 produced earlier East Asian summer monsoon (EASM) onset and northward jump of western Pacific subtropical high (WPSH), leading to the earlier start of the rainy seasons and occurrence time of the precipitation annual peaks over eastern China comparing with the observation and BCC_CSM1.1 m simulation. The improved EASM onset and northward jump of WPSH in BCC_CSM1.1 m model resulted in better simulation of precipitation seasonal transition and occurrence time of the precipitation annual peaks. However, compared to BCC_CSM1.1 model, the much more underestimated summer precipitation over most eastern China in BCC_CSM1.1 m model is mainly due to the weakly simulated northeastward water vapor transport, which is resulted from the much stronger WPSH with farther northwest location and weaker land‐sea thermal contrast.