Climatic characteristics of extreme temperature events in recent 40 years in Anhui

Using daily maximum, minimum and mean temperature data at 77 stations in Anhui province from 1975 to 2014, the temporal and spatial distribution characteristics of extreme temperature events were analyzed. The results showed that the occurrence frequency of extreme cold events in winter has significant regional dependence, which is greater in the north than in the south, and the most frequently is in Anhui, Xiaoxian. The decrease trend of occurrence of extreme cold events of near 40 years was significant, corresponding to the significant increase trend of winter mean temperature. The annual variation of extreme minimum temperature was not obvious, and the frequency and intensity of extreme cold events do not correspond to each other. During the period from 1975 to 2014, the occurrence of extreme warm events in summer is mainly located in the south, and it had an increase trend although it was not significant. The time series of the extreme maximum temperature of the year is corresponding to the time series of the occurrence frequency of extreme warm events. From the analysis of MK mutation, the fluctuation of extreme cold events and extreme warm events both had a point mutation. The analysis of synthetic circulation field showed that the occurrence of extreme cold events in winter is closely related to the meridional dimensions of the circulation in high latitudes of Asia, while the occurrence of the extreme warm events in summer is greatly affected by the obvious westward extension and maintenance of the subtropical high.