Variability and Trends of High Temperature, High Humidity, and Sultry Weather in the Warm Season in China during the Period 1961-2004

Using the daily maximum air temperature and mean humidity observations at 394 surface weather stations across China, the changes in the annual number of days of high temperature weather (HTW), high humidity weather (HHW), and sultry weather (STW) in China over the period 1961-2004 are studied. The results indicate that there were considerable spatial differences and temporal variability of HTW, HHW, and STW across China. Under a climatic mean condition, a notable feature is that southeastern China is the region of collocation of high values of the annual number of days of HTW, HHW, and STW, as well as the region of the most significant variabilities of these parameters. About 55% of the stations in China have increasing trends of the annual number of days of HTW. Most stations in China show decreasing trends of the annual number of days of HHW and are mainly located either in the area south of 30 degrees N or in northern and northeastern China. The stations with increasing trends of the annual number of days of STW are mainly located in northern China, while the stations that have decreasing trends are primarily located in southern China. The analysis results suggest that the variability of the annual number of days of STW corresponds mainly to HTW, and less to HHW. The change in the East Asian monsoon may be responsible for the changes of these statistics in extreme weather in China.