Proceedings of the Thirty-second (2022) International Ocean and Polar Engineering Conference
Shanghai, China, June 5–10, 2022
Copyright © 2022 by the International Society of Offshore and Polar Engineers (ISOPE)
ISBN 978-1-880653-81-4; ISSN 1098-6189

www.isope.org

Evaluation of precipitation simulations in CMIP6 models over the Yangtze Delta, China
Jiayue Gu1, Shuguang Liu1, Zhengzheng Zhou1, Sergey R. Chalov2, Jiyu Liang1, Qi Zhuang1, Shihua Liu3, Anboyu Guo4
1 Department of Hydraulic Engineering, College of Civil Engineering, Tongji University

Shanghai, Shanghai, China2 Hydrology Department, Faculty of Geography, Lomonosov Moscow State University,Moscow, Moscow, Russia
3 Department of Atmospheric and Oceanic Science, Fudan University

Shanghai, Shanghai, China
4 National Marine Environmental Forecasting CenterBeijing, Beijing, China

ABSTRACT(IPCC) Assessment Reports.

The rainfall simulation in General Circulation Models (GCMs) is crucial
in hydrological applications. In this study, the accuracy of rainfall from
15 GCMs in CMIP6 is evaluated over the Yangtze Delta. The results
demonstrate that these GCMs can reproduce the seasonal cycle. However,summer rainfall is underestimated by 70% GCMs, and the increasing
trend of rainfall amount is not captured by most of the GCMs. Overall,
NorESM2-LM, EC-Earth3, CanESM5, IPSL-CM6A-LR arerecommended models applied to the Yangtze Delta. The evaluation
results provide fundamental information to future rainfall projection andchange in flood risk due to climate change.

The evaluation of CMIP models is a significant work. The precipitation
simulation in China was evaluated, starting with the release of CMIP3models (Miao et al., 2012; Chen and Sun, 2015), and illustrated thesimulation of CMIP3 models generally underestimated the Plum Rain
phenomenon for the Yangtze basin area (Tu et al., 2015). Later, Chen andSun (2015) demonstrated the advantage of CMIP5 over CMIP3 in China.
And Kusunoki and Arakawa (2015) considered due to the improved
representation of the western Pacific subtropical high (WPSH) in theCMIP5, models in CMIP5 showed higher skill in simulating summer
rainfall than CMIP3 over East Asia, however, CMIP5 models still
underestimate the precipitation in the warmer season (May-September).
Huang et al. (2013) indicated 14 CMIP5 models spread most in earlysummer over the Yangtze River basin, which is attributed to theuncertainties in simulating large-scale circulations, e.g. WPSH and East
Asian Summer Monsoon. Model resolution (Wang et al., 2017) andphysical parameterizations (Qian et al., 2015) also influence simulation
results. Relatively, multi-model ensembles (MME) have better ability
than individual ones (Chu et al., 2015). A further selection of higher-skill
models can yield a more reliable projection than MME (Kwon et al.,2019).

KEY WORDS: CMIP6; Yangtze Delta; precipitation simulation; model
evaluation; summer rainfall; China.

INTRODUCTION
Presently, climate change has become a great challenge for human society(IPCC, 2022). Under the impact of climate change, the rainfall
characteristics are varying temporally and spatially. Precipitation-related
disasters like floods have enormous impacts on agriculture, water
resource management, and transportation. The Yangtze Delta is one of
the most developed and densely populated metropolitan clusters in China,
which is also vulnerable to flood disasters. Plum rain and tropical
cyclones, e.g. typhoons, inducing the flood events, result in hugeeconomic loss in the region (Zhu et al., 2021). Thus, studying
precipitation in the flood season and providing reliable rainfall patterns
under future climate change are of great importance in this region.

The current output is phase six of the CMIP project (CMIP6) (Eyring etal., 2016). The models have an additional value in the parameterization
schemes for the climate system's major physical and biogeochemical
processes compared to the previous version of CMIP5 (Taylor et al.,2012). CMIP6 models were demonstrated to exceed the performance ofCMIP5 in simulating extreme precipitation in China (Zhu et al., 2020;Luoet al., 2022). The ability of the current CMIP6 models at a regional scaleis also crucial for hydrological response under climate change andregional flood control projects.

General circulation models (GCMs) generate atmospheric variables inhistory and under future scenarios, are important tools in climate change
studies. The World Climate Research Programme (WCRP) established
the Coupled Model Intercomparison Project (CMIP) to compare GCMs
worldwide and standardize climate simulation outputs. The CMIPs form
the data foundation of the Inter-governmental Panel on Climate Change

Thus, this study focuses on the evaluation of the precipitation simulationsin CMIP6 models over the Yangtze Delta. The monthly rainfall data for
1961-2014 in the historical experiment of 15 GCMs in CMIP6 are2438