| Impact of global warming on the climate system changes will continue in the future. However, climate change and natural disasters is related to a certain extent. Climate change and natural disasters have become the focus of scientific research. Due to the nature of the unique geographical conditions and climate type complex in western China, so there are many local rainstorms, floods and other natural disasters. The occurrence of these disasters has caused adverse effects on the production and people' life, bring hidden trouble to people's life and property. Therefore, it is important to study the temporal and spatial variation characteristics and statistical regularity of flood in western China.According to the meteorological data of 231 stations in western China, the characteristics of climate change were analyzed by using Mann-Kendall test method, Kriging difference method, sliding t test methods. According to the historical data records, the frequency, level, seasonal distribution of flood were analyzed. To determine the level and distribution of flood year using the Z index of drought index and drought flood index. Using methods of commensurability calculation, butterfly structure, symmetry structure system to explore the symmetry rules and future trend of floods. Correlation between waterlogging sunspot activity, ENSO and the western region and influence are discussed by using the method of frequency analysis. The main conclusions are:(1) The seasonal and annual temperatures showed a rising trend in varying degrees in 1960-2014, the changes in annual temperature experienced the process of drop rise and decline in the western region of China. The temperature of western China, arid and semi arid area of northwest China, arid area of Xinjiang, humid region of southwestern China mutated respectively in 1993,1992,1992,1999. In space, the annual and seasonal temperature showed a warming trend, the highest annual temperature was in the southeast, the lowest annual temperature was in Tibetan Plateau. In the season, southeast temperature was the highest in spring and autumn, Tibetan Plateau was the lowest. Northwest and southeast temperature was the highest in summer, Tibetan Plateau was the lowest. The highest temperature higher in winter was in the southeast, the lowest annual temperature was in Tibetan Plateau and northwest.(2) The annual precipitation of western China, arid and semi arid area of northwest China, humid region of southwestern China showed a decreasing trend. However the annual precipitation of arid area of Xinjiang and alpine and cold region of Qinghai Tibet showed a rising trend. In the season, the precipitation in summer and autumn showed a decreasing trend, while in winter and spring is increased. In space, the seasonal and annual precipitation was decreasing from southeast to northwest. Annual precipitation had a decreasing trend in humid region of southwestern China and arid and semi arid area of northwest China, while alpine and cold region of Qinghai Tibet and arid area of Xinjiang showed increasing trend. Except autumn, precipitation in spring, summer, winter showed an increasing trend.(3) Flood frequency of western China showed an increasing trend in history. Among them, the most prone to waterlogging was in Chongqing with the average 1.1 years flood occurred 1 times. The flood disasters occurred on average two years in Yunnan, Gansu, Ningxia, Guizhou. The flood disasters occurred on average three years in Xinjiang and Qinghai. The flood disasters occurred on average four years in Xizang, Inner Mongolia, Shaanxi. In the flood degree, the highest frequency was middling flood; heavy flood was the lowest frequency. The seasonal distribution of waterlogging difference was very obvious. The largest distribution of flood was in summer, the flood almost had not occurred in spring and winter.(4) In the recent 54 years, flood frequency showed an increasing trend in western China, arid area of Xinjiang, alpine and cold region of Qinghai Tibet. However, flood frequency showed a decreasing trend in arid and semi arid area of northwest China and humid region of southwestern China. The frequency of seasons flood showed increasing trend. The frequency of annual flood increased in western China and arid area of Xinjiang after the abrupt change of temperature. However, the frequency of annual flood decreased in arid and semi arid area of northwest China and humid region of southwestern China. Flood frequency of western China and arid area of Xinjiang increased in all seasons, flood frequency of arid and semi arid area of northwest China increased in summer, flood frequency of humid region of southwestern China increased in summer and winter.(5) The Symmetry rules of flood were not obvious in western China. The Symmetry rules of flood were best in arid area of Xinjiang, the Symmetry rules of summer floods in arid and semi arid area of northwest China, spring floods in alpine and cold region of Qinghai Tibet, winter floods in humid region of southwestern China were the better. In western China the judgment of the trend of the annual floods, spring floods, summer floods, autumn floods, winter floods were 2017,2016,2017,2020, 2015. In arid and semi arid area of northwest China the judgment of the trend of the annual floods, spring floods, summer floods, autumn floods, winter floods were 2016? 2015?2017?2016?2015. In arid area of Xinjiang the judgment of the trend of the annual floods, spring floods, summer floods, autumn floods, winter floods were 2017?2016? 2016?2017?2019.In alpine and cold region of Qinghai Tibet the judgment of the trend of the annual floods, spring floods, summer floods, autumn floods, winter floods were 2015?2016?2016?2015?2016. In humid region of southwestern China the judgment of the trend of the annual floods, spring floods, summer floods, autumn floods, winter floods were 2015?2019?2016?2015?2018.(6) Flood frequency of western China and alpine and cold region of Qinghai Tibet was biggest in sunspot valley around the year and rising stage. Flood frequency of arid and semi arid area of northwest China and humid region of southwestern China was biggest in sunspot valley around the year. Flood frequency of arid area of Xinjiang was biggest in descending segment. On the contrary in alpine and cold region of Qinghai Tibet, the Z index was positively correlated with the sunspot number in western China, arid and semi arid area of northwest China, arid area of Xinjiang, humid region of southwestern China. Floods and ENSO events happened at the same times, and LA Nina Nino was more than EL. Except arid area of Xinjiang, the Z index showed a negative correlation with the ENSO event in western China, arid and semi arid area of northwest China, alpine and cold region of Qinghai Tibet, humid region of southwestern China.This study analyzed the statistical law of historical flood in western China. Under the background of climate change from 1960 to 2014, this paper discussed the annual and seasonal scale symmetry and the future trend of the flood in western China and each district, in order to provide reference for scientific prevention and management, government's decision making and practice of agricultural production. |
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