The Statistical Law And Symmetry Structure Of Meteorological Drought In Western China

The types of natural disasters are varied in western China,which are mainly drought disasters.Due to the long duration of the drought and a wide range of occurrence,drought is serious.There is the relatively backward economic level,a wide range of soil erosion,the deterioration of ecological environment,serious desertification and so on in western China.Due to the long suffering the harm of drought and drought mitigation capacky shortage,therefore,this article find the drought disaster of the thmporal and spatial characteristic and the statistics law to provide scientific basis and reference for the effective drought mitigation.The main contents of this paper can be divided into four aspects,one is analysis of thmporal and spatial variation of climatic factors(thmperature and precipitation)in the western China,second is analysis of historical period and modem period of spatiotemporal characteristics of drought in the western China,third is to judge the trend of drought disaster in the Western China,forth is the degree of correlation between the analysis of natural environment and drought disaster.(1)In the annual scale,climate change of westhrn China region presented a warming and wetting trend.From the divisions,western China showed obvious difference between the east and west.Humid region of southwestern Ghina and arid and semi arid area of northwest China presented a warming and drying trend.Desert region of Xinjiang and alpine and cold region of Qinghai Tibet presented a warming and wetting trend.Arid and semi arid area of northwest China began to change into arming and wetting trend after the abrupt change of temperature.(2)In the quarter scale,the spring and winter presented a wanning and wetting trend,summer and autumn presented a warming and drying trend.The whole region,humid region of southwestern China,arid and semi arid area of northwest China and desert region of Xinjiang in spring turn into warming and drying trend,but the cold region of Qinghai Tibet become warming and wetting in autumn.The whole region and desert region of Xinjiang turn into warming and drying trend in summer,humid region of southwestern China and alpine and cold region of Qinghai Tthet in summer turn into wanning and wetting trend,arid and semi arid area of northwest China turn into colding and wetting trend. The whole region and each partition become warming and wetting in autumn. The whole region become colding and wetting in winter, humid region of southwestern China turn into warming and drying trend, arid and semi arid area of northwest China and desert region of Xinjiang turn into colding and wetting trend, alpine and cold region of Qinghai Tibet turn into warming and wetting trend.(3) The annual average drought coverage was 28.2% in western China, showing a clear downward trend. And the drought grade was light drought. However, in recent 54 years, the annual average drought coverage was 59.6%. The drought grade was heavy drought. In space, Drought grade is approximately expressed as the distribution characteristics of the southeast low, northwest high. The region's seasonal drought severity, the occurrence of a wide range and the drought grade was heavy drought. But heavy drought coverage decreased significantly, where drought and winter drought most extensive and severe.(4) In the annual scale, humid region of southwestern China was the most mild drought area, which drought range of small, low severity. And winter drought was the most serious. Arid and semi arid area of northwest China seasonal drought was serious. The drought occurred in a wide range, a higher level of severity. Seasonal drought was serious in Desert region of Xinjiang, which wide range and drought severity. Alpine and cold region of Qinghai Tibet was the most serious drought in the region of Western China. But the severity of desert region of Xinjiang and alpine and cold region of Qinghai Tibet presented the obvious trend of rapid decline.(5) From the overall perspective, the whole region may occur heavy drought in large range in autumn and winter of 2015, heavy drought in large range may occur spring and summer of 2016, the large scale range of drought may occur in 2017. From the view of partition, years of large-scale drought of humid region of southwestern China may occur in 2015. There may be a wide range of drought in spring. Winter is likely a wide range of heavy drought. And a wide range of drought may occur in autumn of 2016. Arid and semi arid area of northwest China occurs in large scale heavy drought in the summer of 2016, and a wide range of drought may occur in autumn. Desert region of Xinjiang occur wide range of drought in the winter of 2015. Alpine and cold region of Qinghai Tibet occur in large scale middling and heavy drought in the autumn of 2015, a wide range of drought may occur in the summer of 2016.(6) When the sunspot number increases, drought coverage of the whole region and the partition decreased significantly. In El Nino years, drought coverage is relatively large, on the contrary in La Nina years.This paper analyzed the different temporal and spatial scales of drought coverage, indicating that the drought coverage can effectively reflect the regional drought severity. It can link the time scale from 1470 to 2014 by using the drought coverage. It also can carry out the correlation analysis and statistical test by constructing a multiple sequence of drought coverage, sunspot number and ENSO events so that it can be more statistical significance and higher confidence level.