Shaanxi Province, Extreme Temperature Changes Characteristic Analysis

With the further study of global climate change,people have gradually realized that the impact of extreme climate events on human daily production and life,socio-economic, ecological environment,which often exceed climate change does.Based on the data of daily maximun temperature,minimun temperature and average temperature from 22 meteorological stations in Shaanxi Province from 1960 to 2005,the features of extreme temperature are studied. Some classical statistical methods have been used to study characteristics of extreme temperature change,such as trend, anomalies, Mann-Kendall mutation test,Morlet wavelet analysis,correlative correlation and so on.The main findings are as follows:(1)The mean temperature are on the rose in Shaanxi Province from 1960 to 2005,about 0.855℃for the 45 years.The highest of value added is from 80's to 90's,the warming showed the characteristics of strong North weak South.The average temperature mutation occurred in 1993 in Shaanxi Province,and respectively occurred in 1994 in Shaanbei and 1995 in Guanzhong,but there is no mutation occurred in Shaannan,only a big turning point in 1997.0n 33 years time scale, there are about 15 years of alternating cold and warm change in Shaanxi Province.(2)The average maximum temperature and minimum temperature also showed a significant warming trend,the latter is larger than the former in Shaanxi Province, the warming is mainly caused by the increase of minimum temperature.Various natural areas in the province showed different growth temperature trend,the warming amplitudes of annual maximum temperature is greater than annual minimum temperature in north and south of Shaanxi,but there is different in the Central Shaanxi.On average conditions, the annual mean minimum temperature mutation occurred in 1993, the annual average maximum temperature mutation occurred in 1995,the maximun occurred in 1994 in Shaanbei and Guanzhong,there is no temperature mutation in Shannan,only a big turning point in 1997.From north to south,the annual mean minimum temperature mutations respectively occurred in 1993,1994, and 1997,it is much earlier in north. The variation cycle of maximun temperature and minimum are all 15 years.(3)As like as the number of days with maximum temperature above 35℃,the number of days with minimum temperature blow 0℃in Shaanxi Province had a decreasing tendency from 1960 to 2005.Compared with the North of China,the reduce amplitude of high temperature days is much smaller,but the reduce amplitude of low temperature is stronger. The number of high temperature days is increasing with a rate of 0.62 days every 10 years in Shanbei, which is seriously going against the control of drought and desertification, and ecological development of the area. The frost season reduced about 15 days in Guanzhong area, which would have a major impact on agriculture and natural environment.(4)The number of days with daily maximum temperature above 95th percentiles in Shaanxi Province is increasing,but it was more obvious after the mid-80s,and the mutation occurred in 1996.The increasing trend in Shanbei and central and west of Guanzhong area was more significant. There is a significant 6-8 year periods in 1960-2005 years. At the same time, the number of days with daily minimum temperature blow 5th percentiles in Shaanxi Province is also greatly reducing. The declining trend in central and west of Guanzhong area was the most significant. The mutation occurred in 1990-1992,which is earlier than the extreme high temperature. There is around 6 years oscillation cycle.(5) There are abvious positive relations between average temperature and the number of days with daily maximum temperature above 95th percentiles,and the abvious negative relation between average temperature and the number of days with daily minimum temperature blow 5th percentiles.Compared with annual mean temperature, seasonal average temperature had more significant correlation to the extreme temperature events.