Characteristics of identification and evolution of regional rainstorm and drought processes in Anhui Province during 1961-2020

Identifying objectively the processes of regional climate events and evaluating quantitatively their intensity are the basis for accurately monitoring and assessing the impacts of events. Using the data of daily mean precipitation and temperature from 80 national meteorological stations in Anhui Province during 1961-2020, the processes of regional extreme climate events are identified. According to the averaged intensity, duration and average influence range, the intensity evaluation model of regional process is constructed and the intensity grade is divided by the percentile method. The 775 regional rainstorm events are captured, and the annual average frequency is 12.9 times during 1961-2020, including 34 extremely strong regional events, about once in two years. The average duration of single regional rainstorm event is about 1-2 days, and the daily average spatial coverage of a single event covers 37 stations. The frequency and intensity of regional rainstorm event has increased significantly in nearly 60 years. In the past 60 years, there have been 152 regional drought events in Anhui Province, including 9 extremely strong regional events with a return period of about 6~7 years. The average duration of single regional drought event is about 15-60 days. The linear change trend of annual frequency of regional drought event is not obvious, but the inter-annual variation is large. Compared with the summary of climate monitoring services and historical cases, the assessment model is reasonable and consistent with historical extreme cases, having good correspondence with historical disaster data in time, range, and intensity. This index will provide a reference for the quantitative assessment of regional extreme climate events in other areas, and it is also an important technical support for timely monitoring and early warning for the extreme climate events.