Characteristics Analysis and Synoptic Features of Event-Based Regional Heatwaves Over China

Extreme weather is a global challenge due to its severe impact on environment and society. Existing studies focus on specific extreme events or long-term characteristics of individual indices. Event-based concept was proposed to more accurately understand features of extreme events and achieve results closer to realistic extreme processes. In this study, the event-based concept was extended to spatial dimension to simultaneously investigate multiple features in space and time. After homogeneous regions were identified, extreme events in each region were clustered into different types and then subsequent statistical analyses were conducted. The event-based concept provides further insight into potential driving mechanisms by synoptic features analysis. To evaluate our framework, heatwave in China was chosen as a case study due to its severe impact on socioeconomy and China's complex topography and climate. The results revealed details about the regional features in northwest China and vast spatial extent along the middle and lower Yangtze River. Different heatwave types showed different characteristics in different regions. Severer heatwaves generally had larger magnitude in various features. Synoptic feature analysis revealed that heatwave events in northwest China were influenced by the Iranian Subtropical High and surface temperature advection from the Qinghai-Tibet Plateau. The western Pacific subtropical high impacts the heatwave events in eastern China. The western spread of the subtropical high and cold waves from north spawn and finish heatwaves in Sichuan Basin. The correlation analysis between circulation anomalies at the start of heatwaves and the overall features of events was concluded in the most heat-impacted region.