Abstract:Based on daily precipitation and temperature data from 125 observation stations in Yunnan Province from 1961 to 2024, as well as NCEP/NCAR daily reanalysis data of atmospheric circulation in upper and lower levels, this paper investigates the criterion for the persistent drought events across winter and spring (WSPDE) in Yunnan. By analyzing the spatio-temporal characteristics of WSPDE in Yunnan, we have found that the WSPDE distribution in Yunnan is characterized by more in the northwest but less in the southeast. The regions with the highest drought frequency are mainly concentrated in the eastern part of northwest Yunnan, including Lijiang, Dali, and northern Chuxiong, while the southern parts of Honghe and Xishuangbanna have less drought events. The WSPDE standards for single station and provincial region in Yunnan are defined as follows. The station standard refers to the occurrence of light or above level drought in both winter and spring in a year, with moderate or above level drought occurring in one of two seasons. When 25 observation stations (20% of the total number of stations in Yunnan) experience the WSPDE in a year, and the average precipitation anomaly percentage in both winter and spring is ≤-10%, it is defined as a provincial WSPDE in Yunnan. Comparative analysis shows that this criterion can be reasonably used in identifying WSPDE in Yunnan. Further analysis reveals that the sustained maintenance of the geopotential height difference with high in the north and low in the south of the mid-low latitudes region at 500 hPa in East Asia, as well as anomalous anticyclones at 700 hPa in the Bay of Bengal has a significant impact on the WSPDE in Yunnan. The standard has an important scientific significance and application value for standardizing the WSPDE criterion for climate monitoring and prediction operations in Yunnan.