Advantages of a variable‐resolution global climate model in reproducing the seasonal evolution of East Asian summer monsoon

Abstract

The East Asian summer monsoon (EASM) is unique among monsoon systems that it features meridional evolution of the summer monsoon. In this study, we evaluate the performances of a Variable-Resolution Community Earth System Model (VR-CESM) regionally refined over eastern China (14 km) in reproducing the seasonal evolution of EASM precipitation over China.Compared with reference datasets, VR-CESM shows better performance than the corresponding globally uniform coarse-resolution model CESM (quasiuniform 1°), especially over western China where complex local topography exists. The northward monsoon migration is closely related to low-level southerly flows and vertical moisture advection, which are more reasonably simulated in VR-CESM. The four critical timings of the EASM (monsoon onset, withdrawal, peak, and duration) are also better captured in VR-CESM than in CESM. The corresponding spatial Pearson correlation coefficients of the four critical timings with respect to reference datasets are about 0.1 higher in VR-CESM than those in CESM. Both models are most accurate in simulating monsoon onset and least accurate at simulating the monsoon peak. The overestimated zonal thermal contrast in CESM is responsible for the earlier monsoon onset and excessive precipitation in September over the Yangtze River valley. Finer resolution in VR-CESM, especially over the Tibetan Plateau (TP), appears to be a main factor in simulating better zonal thermal contrast and seasonal evolution of the EASM.

Exploring the Influence of Improved Horizontal Resolution on Extreme Precipitation in Southern Africa Major River Basins: Insights from CMIP6 HighResMIP Simulations

“…Secondly, we assess the influence of horizontal resolution on the performance of the CMIP6 HighResMIP models in simulating extreme precipitation without considering mechanisms associated with improvement and deterioration in HR model's performance relative to their LR counterparts. Previous studies on model evaluation in simulating precipitation have focused solely on the main rainy seasons (e.g., monsoon; Liang et al, 2023;Tamoffo et al, 2023;Zhu et al, 2023) due to their higher influence on extreme precipitation compared to other seasons. The results of this study reveal that the improvement in model performance resulting from enhanced horizontal resolution varies with precipitation indices, suggesting that assessing the influence of horizontal resolution in atmospheric circulation alone is insufficient to understand the mechanisms associated with improvement and deterioration in HR model performances.…”

Understanding Surface Air Temperature Cold Bias Over China in CMIP6 Models

“…The monthly SAT data sets from CN05.1 (simplified as CN05) and Climatic Research Unit (CRU) Time Series version 4.07 are both used to evaluate the model performance. CN05 with a horizontal resolution of 0.25° × 0.25° (longitude × latitude) is widely applied in the evaluation of GCMs (e.g., Guo et al., 2020; H. Zhu et al., 2022), which is interpolated based on 2,416 stations and established by the Chinese National Climate Center (J. Wu & Gao, 2013). CRU is a monthly high‐resolution multivariate climate data set on a 0.5° longitude by 0.5° latitude grid, which spans 1901−2022 (Harris et al., 2020).…”