| Weather disasters are the most frequent and severe disasters among the natural disasters,with the trend of global warming intensifies,the frequency of extreme weather and climate events such as drought,flood which impact China are higher,the damage cause by it are stronger,the range of influence cause by it are larger.The extreme weather and climate events which once in several yeares,once in 100 yeares or once in more than 100 yeares are continue to occur,even become a serious threat to people's normal life and social safety.With the climate change,people pay more attention to the extreme climate events and the development of feasibility study of climate,the study of spatial and temporal distribution and its impact of extreme climate events such as extreme maximum temperature,extreme minimum temperature,daily maximum precipitation,annual precipitation has become more urgent.This thesis take ArcGIS as the main tool,combined with DEM and mathematical statistical methods,probe and distinguish the spatial interpolation methods of history extreme temperature and precipitation data which observed by meteorological stations of Shaanxi Province,the conclution has been verified through scientific methods,after this,the characteristics of the spatial and temporal distribution of extreme temperature and precipitation of Shaanxi Province has been analyzed.Through the Visual Basic programming,the methods of calculation the different return periods of precipitation and other meteorological factors has been selected,the spatial distribution of extreme temperature and precipitation of Shaanxi Province has been given by adopt scientific method,the corresponding quantitative analysis results has been given too.Conclusions were as follows:1.The extreme maximum temperature of Shaanxi Province appears in June and July mostly, which appears in December and January mostly,there has significant regional differences.The characteristics of inter-annual extreme temperature are obvious from 1951 to 1982.After 1983,the annual extreme maximum temperatures show a clear upward trend.The inter-annual variation of extreme minimum temperature is obvious;from 1951 to 2007 the extreme maximum temperature in various regions has upward trend.2.The daily maximum precipitation of Shaanxi Province appears in June,July and August mostly,the difference between each month is very large,and it has no significant characteristics of less in North and more in South.Annual precipitation has the significantly characteristics of less in North and more in South,and inter-annual characteristics is obvious.Take Yulin,Yan'an, Xi'an,Ankang,Hanzhong as the representative site,the annual precipitation of Ankang is increased slightly from 1951 to 2007,and the remaining four years showed a decreasing trend.3.In considering the influence of altitude,whenever extreme maximum temperatures or extreme minimum temperature,the effect of interpolation by using ordinary Kriging method is best. The S_f~2,R_f and K_f of Return periods of extreme temperatures calculated using Weibull distribution is smallest and the effect is best.In the selection of interpolation methods of extreme precipitation,the method of radial basis function is best.The S_f~2,R_f and K_f of Return periods of extreme precipitation calculated using the methord of extreme value type I distribution which estimated by moment parameters is smallest and the effect is best.4.The regional differences of return period of extreme maximum and extreme minimum temperature of Shaanxi Province is obvious,Once in 15 years is mostly during 34～42℃,88.92% of total area.Once in 30 years is mostly during 34～42℃,87.11%of total area.Once in 50 years is mostly during 36～42℃,76.76%of total area.Once in 100 years is mostly during 36～44℃, 88.83%of total area.The extreme minimum temperatures of once in 15 years is mostly during -11～-29℃,72.98% of total area.Once in 30 years is mostly during -11～-29℃,74.30%of total area.Once in 50 years is mostly during -11～-32℃,87.63%of total area.Once in 100 years is mostly during -14～-32℃, 72.80%of total area.5.The daily maximum precipitation of once in 15 years in most areas of Shaanxi Province are between 75.0～200.0mm.Once in 30 years in most areas of Shaanxi Province are between 75.0～225.0mm.Once in 50 years in most areas of Shaanxi Province are between 10.0～250.0mm.Once in 100 years in most areas of Shaanxi Province are between 100.0～300.0mm.Among them, Zhenba of Hanzhong and Ziyang of Ankang and other small area in Ningshan are the largest value areas of daily maximum precipitation of return period.The daily maximum precipitation of once in 30 years or above in most areas of Shaanxi Province has reached the heavy rain standard.Once in 100 years in some areas has reached the ultra-heavy rain standard.The annual maximum precipitation of once in 15 years in most areas of Shaanxi Province are between 40.0～1900.0mm.Once in 30 years are between 500.0～2200.0mm.Once in 50 years are between 500.0～2100.0mm.Once in 100 years are between 600.0～2400.0mm.The spatial distribution of annual maximum precipitation of once in several years of Shaanxi Province shows a clear ladder-like characteristic,the annual maximum precipitation are decreased from south to north,there are several large values district which appears in the Zhenba and Ningqiang of Hanzhong.In this thesis,there has some innovation in following aspects:1.The study of temperature and precipitation which is the basic reflection of weather and climate has been developed,the temporal and spatial distribution extreme weather and climate elements in Shaanxi Province has been given,it can provide a reference for various sectors of society,and provide corresponding data support and scientific basis for disaster prevention.There has little similar literature so far,so it has a certain degree of innovation.2.Through programming,the use of ArcGIS software,combined with DEM and the selection of calculation methods and interpolation methods for meteorological factors of different return periods,this thesis analysis the spatial and temporal distribution characteristics of meteorological elements and its return period value,the quantitative conclusions are given.All above gives the solution ideas about similar analysis on the future,there has some innovation. |
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