Physical processes of summer extreme rainfall interannual variability in Eastern China—part II: evaluation of CMIP6 models

Sarah Sparrow,Simon F B Tett,Buwen Dong,Nicolas Freychet,Sihan Li,Fangxing Tian

doi:10.1007/s00382-022-06137-z

Abstract

Eastern China is regularly exposed to extreme precipitation with significant socio-economical consequences. Following an observational analysis in a first part of this study, here the ability of the Coupled Model Intercomparison Project Phase 6 models to reproduce the main modes of interannual variability of 5-day summer extreme precipitation over eastern China is evaluated, using an empirical orthogonal teleconnection (EOT) method. These models capture the main patterns and magnitudes of the different EOT patterns, although the North China mode is less well represented. Models also reproduce the dynamical features associated with each mode. There is no systematic improvement in the ability of models to simulate either the pattern or the 5-day intensity when using higher resolution models compared to coarser resolution ones. Instead, multi-member or multi-model ensembles lead to results closer to observations. Using a low mitigation projection pathway (SSP-370), it is shown that the risk of the most extreme 5-day precipitation events by about 40%, 80% and more than 150% for global-mean warming levels, relative to 1850–1900, of + 1.5, + 2 and + 3 ^{circ }C respectively. This increase is found to be more significant for 5-days events than for seasonal scale precipitation, consistent with previous studies.

Highlights

Heavy persistent precipitation has a large impact on society and agriculture
This paper aims to answer the following questions: Can the Coupled Model Intercomparison Project Phase 6 (CMIP6) climate models, when ran with historical forcings Gillett et al (2016), reproduce the observed persistent precipitation signal over Eastern Chinese Academy of Sciences (China)? If so, are they reproducing the signal for the right reasons? And what are the expected future changes in risk?
Following the work of Tian et al (2021), we conducted an evaluation analysis for the latest version of the Coupled Model Intercomparison Project, CMIP6. These results are complementary to Zhu et al (2020) who investigated CMIP6 performances for different extreme precipitation indices

Summary

Introduction

Heavy persistent precipitation has a large impact on society and agriculture. It can cause flooding, crop loss, landslides and other major disruptions such as the events along the lower reaches of the Yangtze River in China in May 2016 (Li et al 2018a) or during the winter of 2018/2019 (Hu et al 2021). Du et al (2019) indicated that persistent extremes were increasing in most regions globally. China is exposed to heavy precipitation and has experienced intensified events during the past decades (e.g. Li et al 2012; Zhai et al 2005; Qian et al 2007; Gu et al 2017). Compared to short lasting extreme precipitation, e.g., those related to tropical cyclones (e.g. Pei et al 2018), sustained precipitation over several days is often related to the monsoon seasonal circulation (Wu et al 2019). Eastern China is vulnerable to this type of persistent precipitation, as highlighted by many recent studies (e.g. Chen and Zhai 2013; He and Zhai 2018)

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Results

Conclusion