Present and future climate of the Yangtze River Delta region: analysis of the CMIP6 HighResMIP simulations

Global warming is incurring diverse climate changes across different regimes, where high-resolution models provide valuable insights of the regional climate changes for guiding social adaptation and mitigation. Thus, this study is aimed to investigate the capability of high-resolution models in simulating the historical climate (1980-2014) over the Yangtze River Delta (YRD) region, and examine the possible regional climate change in the near future (2031-2050). Data from the highresSST-present and highresSST-future experiments of 5 CMIP6 HighResMIP models (FGOALS-f3-H, HiRAM-SIT-HR, NICAM16-8S, MRI-AGCM3-2-S, and MRI-AGCM3-2-H) were analyzed together with the daily station observations by China Meteorological Administration. Results show that the models generally well simulate the regional means and extreme events of the daily-mean temperature and precipitation over the YRD region for the historical period. The temperature is underestimated in the southern YRD (especially in summer and autumn), causing underestimated meridional gradient. In contrast, the precipitation spatial distribution closely matches observations in all seasons, showing a marked improvement over results from low-resolution models. For the near-future period, the daily-mean temperature is projected to increase by 1.4 degrees C, which nearly persists throughout the year and is only slightly milder in winter. The daily-mean precipitation may increase by 0.2 mm day(-1) (similar to 6%), with the largest increase in summer (0.4 mm day(-1)) and a slight decrease in winter. Meanwhile, the occurrences of extreme hot events and heavy-precipitation events are increased across the YRD region. Given the substantial implications of these possible imminent changes, more effort is warranted to reduce model uncertainties for enhanced validation.