| It has become a common social phenomenon that low temperature, snow disasters, floods and droughts gradually cause wide spread concern because the frequency and strength of extreme climate events affected by the global climate warming is higher, which has lead to more impact on the survival and sustainable development of human society. Western region in China, affected by the monsoon and topography, has obvious differences in the area of the natural environment. Besides, as a sensitive area of climate change and fragile ecological environment which have a certain response with global climate change and a significant impact of eco-systems and the climate, it is important to study the time and space distribution of low temperature and snow disasters.Based on the daily precipitation, highest temperature, minimum temperature and mean temperature data series of 266 meteorological stations from 1961-2014, developing an index system to characterize low temperature and snow disasters, using linear trend method, Mann-kendall mutation test, inverse distance weighted interpolation method(IDW), mathematical statistics, symmetry and correlation analysis and so on, this paper not only reveals the time and space distribution and the occurrence of future trends of low temperature and snow disasters, but also discusses the related influence factors. The main conclusions are as follows:(1) The temperature has witnessed enhanced warming trend and declined low temperature trend of each area in western from 1961 to 2014. AT 10 and ATO showed upward trend with the rate of 6.835?/a and 3.375?/a, while the indices characterizing low temperature (FDO, IDO, TX10P, TN10P, CSDI) showed decreasing trend respectively with the rate of -0.332d/a,-0.172d/a,-0.164d/a,-0.354d/a,-0.146d/a in Western region. Meanwhile, the average of annual PRCPTOT also showed an increasing trend of 0.015mm/a. In addition, AT10 and PRCPTOT showed good testing effect after analysis the mutation testing of indexes in each area of western region. Besides, the mutation points for AT10 respectively in 1998,1995,2002,1996 and 2000 in western region, Northwest Arid and Semiarid Region, southwest region, Tibetan plateau, Xinjiang area all have passed the 0.01 level of significance of the test.(2) AT 10 has the similar spatial distribution with ATO in the western region that low centers located in Southern Qinghai and northern pastoral areas of Tibet Naqu area while high centers located in most of Yunnan, Guizhou, eastern, northeastern Sichuan and Chongqing all area. AT10 trend rate has large differences in the spatial distribution, but ATO trend rate shows such a spatial distribution pattern that high centers lies in Tibetan plateau then gradually declined to surrounding areas. In addition, the spatial distribution of snow disaster indexes overall appears that high centers located in northern region in Xinjiang, southern and eastern areas in Southern Qinghai, northwestern area in Sichuan, and then gradually declined to surrounding area. The snow disaster indexes trend rate shows such spatial distributions that the western and northern are high while eastern and southern are low.(3) Since the Qing Dynasty, the frequency of low temperature and snow disaster show a decasing trend of each area in western China. The rate of recurrence for low temperature (snow disaster) are once every 8.9a (14.1a) in Qing Dynasty while the rate are once every 1,4a (2.3a) after the Liberation in western China. Besides, it has occurred 15 low temperature and 7 snow disaster in the western region since 1961, and appears relatively dispersed international distribution. In addition, the frequency of different levels of low temperature and snow disaster appears obvious different spatial distribution.(4) Low temperature and snow disasters have good symmetry law of each area in Western from 1961 to 2014. Overall, the symmetry rule of snow disaster is better than low temperature. The next low temperature may occur in 2016 in western region, while Northwest Arid and Semiarid Region, southwest region, Tibetan plateau, and Xinjiang area may occur in 2015. Besides, the next snow disaster of light or above may occur in 2016 in western region, Northwest Arid and Semiarid Region, southwest region, Xinjiang area, while Tibetan plateau may occur in 2015. In addition, the next snow disaster of Intermediate or above may occur in 2016 in southwest region, Tibetan plateau, Xinjiang area, while Northwest Arid and Semiarid Region occur in 2029.(5) Sunspots, ENSO events also have clear relationship with low temperature and snow disaster of each area in western region. Low temperature mainly happened in falling section, followed by valley section, while the severity low temperature primarily occurs at the peak and valley segments. But the distribution of snow disasters is different that Northwest Arid and Semiarid Region mainly occur in peak years, southwest region occur in falling section, Tibetan plateau and Xinjiang area occur in rising section. While the snow disaster of Intermediate or above mainly concentrate in the rising segment and peak years. In addition, low temperature and snow disasters mainly occur in the ENSO event of each area in western region, but different level has different law that the frequency of severity low temperature will become more when the ENSO intensity become strengthen, while the frequency of snow disaster of Intermediate or above more happened in normal years than ENSO event.The study mainly discuss the time and space distribution of low temperature and snow disasters in western, analyses the history data statistical processing periods, and have forecast the future trend for low temperature and snow disasters, which can enrich the research for disease judgment and provide certain theoretical basis for regional disaster prevention and relevant government decisions. |
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