大气阻塞在春末夏初北极海冰影响中国东部降水中的作用和变化

全球变暖导致的北极海冰剧烈变化，可通过影响中高纬度大气环流强烈作用于北半球中纬度天气气候。大气阻塞是中高纬度持续性大尺度的经向环流异常，它受到北极海冰的调制，在欧亚大陆的异常活动常对中国东部降水有重要影响。以往关于北极海冰影响中国东部降水的研究较少关注大气阻塞在其中的作用，对北极海冰调制大气阻塞进而影响中国东部降水的物理过程不清楚，相关机制不明确。申请人预研究发现，北极海冰与中国东部降水的年际联系存在阶段性特征并有增强趋势，但不同阶段中大气阻塞异常和其作用未得到揭示。因此，本项目拟聚焦北极海冰快速融化的春末夏初，采用统计分析、动力诊断和数值模拟相结合的方法，探明春末夏初北极海冰异常对大气阻塞的调制作用以及大气阻塞异常对中国东部降水的影响机制，揭示春末夏初北极海冰与中国东部降水关系的阶段性特征以及不同阶段中大气阻塞的异常和作用，为提高我国东部汛期气候预测水平和应对区域性气候变化提供科学依据。

Over the past decades, Arctic sea ice changes dramatically due to global warming. Arctic sea ice's influence on the climate and weather over the Northern Hemispheric midlatitudes is widely concerned in the climate science community. Anomalies in Arctic sea ice and midlatitude weathers are linked by sea ice-induced mid-high latitude atmospheric circulation anomalies such as atmospheric blocking. Atmospheric blocking is a striking phenomenon in the mid-high latitudes with strong and persistent meridional flow modulated by Arctic sea ice. The atmospheric blocking over the Eurasian mid-high latitudes often enhances the rainfall in eastern China, suggesting its essential role in Arctic sea ice affecting midlatitude rainfall. Previous studies highly agree that Arctic sea ice can influence eastern China's rainfall in spring and summer, but large discrepancies exist among their conclusions. Few of them have examined rainfall anomalies caused by the atmospheric blocking anomalies in response to the Arctic sea ice change; thus, the potential role of atmospheric blocking in the Arctic affecting eastern China rainfall is obscure and requires further investigation. Moreover, our pre-study suggests that the interannual relationship between the Arctic sea ice and the Eastern China rainfall has strengthened over the past decades and shows periodic features, of which the underlying mechanism is unclear. This project will focus on the late spring-early summer season when Arctic sea ice is sensitive and undergoes seasonal melting. We aim to reveal how the atmospheric blocking changes in response to the year-to-year Arctic sea ice variability and examine how the eastern China rainfall changes in response to the sea ice-induced atmospheric blocking anomalies. Furthermore, this project will examine the influence of blocking on the changes in the interannual relationship between Arctic sea ice and Eastern China rainfall. Ultimately, this project will improve the flood-season rainfall prediction and future regional climate change strategies in eastern China. Statistical analyses, dynamic diagnoses, and numerical simulations will be used in this project.