Characteristics of Climate Change of Summer Heat Waves in Sichuan Basin during 1961~2016

Based on the daily observational summer maximum temperature data at 27 stations from 1961 to 2016,we have discussed the temporal and spatial variation characteristics of summer heat waves in Sichuan Basin by using the methods of trend analysis and wavelet analysis and so on.The results show that:1) The frequency,intensity and duration of summer heat waves in Sichuan basin present an detectable increase,and the trend of intensity is the most significant.All of them show an distinct decadal revolution of weakly increasing-obviously decreasing in the 1960s to 1980s,while abruptly increasing from the 1990s up to now.2) The spatial distribution of climatic summer heat waves are generally characterized by less (weak) northwest and more (strong) southeast.The features of spatial difference are significant.High frequency and intensity of heat waves are mainly observed in the southwestern Chongqing.In the past 56 years,the summer heat waves in most areas of Sichuan Basin have increased,except for a small part of the southeastern margin areas.The large-value bands of increase are northeast-southwest along the north part of Chongqing to the south of Sichuan province.In contrast,the increase of heat waves in the west part of the basin is more significant than that in the eastern.3) Wavelet analysis indicates that there are significant inter-annual variations in the heat waves frequency,intensity and duration,and they have a relatively consistent two-year cycle.Correlation analyses show that there are significant simultaneous positive correlation between the heat waves and western Pacific subtropical high ridge line and northern boundary.