SPATIAL AND TEMPORAL VARIATIONS OF EXTREME TEMPERATURE EVENTS IN SOUTHWESTERN CHINA DURING 1962-2012

In recent years,the magnitude of global warming was more serious than before,increasing the occurrence frequency of drought,frost and other natural disasters.In Southwestern China,persistent snow,ice storms and persistent drought events attracted a lot of attentions since 2008.Therefore,it is very important to investigate the variation of extreme temperature events and its mechanisms.By using daily maximum and minimum temperature at 88 meteorological stations in Southwestern China in the period between 1962 and 2012provided by China Meteorological Administration,temporal and spatial variation of extreme temperature events were investigated using the methods of regression analysis,MannKendall rank correlation and inverse distance weighted interpolation.Eight indices of extreme temperature were studied.The results indicated that extreme temperature indices were obviously different in spatial distribution.The indices of warm days,warm nights,cold nights,and extra-minimum air temperature decreased gradually from southeast to northwest,with changing rates of 13.1-36.3℃,-1-23.5℃,-15-15.2℃ and-30.6-6.7℃,respectively.Nevertheless the index of frost days increased in the same direction with maximum change over the northwest of Sichuan.Both the distributions of cold days index and extra-maximum air temperature are like a saddle,with the highest values over the southwest and northeast.There were few high temperature days over most areas.Obvious gradient of hot day index can only be seen over central Yunnan.The indices of cold day,frost days and cold nights have significantly decreased by the rate of 2.7d/10 a,3.5d/10 aand 4.9d/10 a,respectively.Warm days indices,warm nights indices,extra-minimum air temperature and extra-maximum air temperature have significant increased by the rate of 1d/10 a,4.7d/10 a,0.4℃/10 aand 0.1℃/10 a,respectively.Only hot days indices did not change significantly.The magnitudes of changes in cold indices are much greater than those in warm indices.The changing ranges of night indices were larger than those of day indices,which indicated that the changes of day and night temperature were asymmetrical.The variation of extreme cold indices showed a downward trend,and that of extreme warm indices showed an upward trend.Their overall performance had a warming trend over Southwestern China.Whereas,the variation range of extreme temperature events was less than other regions of China which reflected the unique feature of climate change over Southwest China.