关键词: 异常高温, 强高温个例, 环流特征

Abstract: The data of day-to-day maximum temperature from June to August during 1960\_2003 that recorded by the 62 meteorological stations were used to the changes of the maximum value, distribution range, and continuous time of high temperature in Gansu province; the grid data of height field and temperature field of four high temperature cases were used to analyze the extreme circulation characteristics in climate history of Gansu province. The results show that, in the west of Gansu, the extreme maximum temperature differs obviously between months; the value in Jane is the lowest and that in July is the highest; there is slight increasing linear trend in July and decreasing linear trend in June and August; the increase of the maximum temperature is not evident in 1990s. In the east of Gansu, the extreme maximum temperature differs little between months; there is increasing linear trend in July and in August; the increase of the maximum temperature is evident from 1995 to 2002. The largest distribution range of high temperature in June occurred in 1960s. The number of years occurred wide range high temperature in July during the late of 1990s was more than that before, and the continuous time of high temperature in July remarkably lengthen in 1990s. High temperature weather will occur when South Asia high on 100 hPa, the warm centre on 300 hPa, and subtropical cell on 500 hPa are simultaneous over the Northwest China and the centers of them are almost vertical.

Key words: extreme maximum temperature, high temperature cases, circulation characteristics