| Under the background of climate warming, drought as a kind of natural disaster whichseriously threats to survival environment of the word human will tend to increase. Easternagriculture region of Qinghai province as the main food crop production areas, drought is themain meteorological disasters that threats to farming and animal husbandry production, whichseriously restricts the sustainable development of agriculture and national economy inQinghai province. So researching the suitable drought indices for eastern agricultural regionof Qinghai province, quantifying the space-time evolution of drought, is of great significanceto plan agriculture planting structure reasonably, to manage water resource effectively and todisaster prevention and mitigation.Typical climatic factors (precipitation, evaporation, and temperature) annual and yeardrought trend change was analysied by meteorological and hydrological sequence form1961-2006at the research area, with adopting various statical methods. Three selected kindsof drought indexes were calculated and compared the drought characteristics to find a suitabledrought index for single station in the study area, then building a regional drought index andresearching the space-time evolution laws of the eastern agricultural region of Qinghaiprovince. The last research was the response of drought to the drought climate change. Basedon the above analysis, the following main conalusions are obtained:(1) The average annual precipitation of the eastern agricultural region of Qinghaiprovince is404.37mm. Precipitation in recent46years experiences from the dry period to thepluvial period, and the overall trend is not obviously falling volatility. On the space, the yearsof average rainfall is reduced from northwest to southeast. Annual precipitation mainlyconcentrated in the summer. There is a significant increase trend of spring and winterprecipitation and a significant decline trend of summer and autumn precipitation. Eachseasonal rainfall spatial distribution tendency rate is higher in the northwest and more lowerin the southeast, and there were some variations in different seasons.(2) The average temperature for many years of the eastern agricultural region of Qinghai province is5.4℃，and the overall trend increases significantly. Each seasonal averagetemperature also increases. Winter average temperature rises significantly, and its growth rateis bigger than annual average temperature, the average temperature of spring, summer andautumn growth is slower than the winter. Year lowest temperature and highest temperaturealso has significant upward trend, the lowest temperature growth rate is greater than highesttemperature, it also causes of the annual average temperature showed a trend of increased yearby year. On the space, annual and various seasonal average temperature, annual highesttemperature tendency rate are higher in the northwest and lower in the southeast, and thetemperature trend rate are all positive. There are some differences at the local regional ofdifferent seasons. Annual lowest temperature’ space characteristic is: the temperaturetendency rate is higher at central region and relatively lower at the west and south region (inaddition to Huang Nan).（3）The average evaporation for many years at the eastern agricultural area of Qinghaiis970.8mm, nearly46years’evaporation ET0has a significant decreasing trend. Averageevaporation’ Space characteristics as follows: Evaporation tendency rate increase fromnorthwest to southeast, annual evaporation had a tendency to increase in southeast, andshowed a decrease trend form northwest to central region. The annual evaporation spatialdistribution is opposite to the temperature and precipitation space distribution. Annualevaporation mainly concentrated in the spring and summer, occupying69%of annualevaporation. Each season evaporation ET0is characterized by declining trend, consistent withthe trend of annual evaporation. Winter evaporation has a significant downturn and the trendof the other three seasons is not significant. Each season evaporation tendency rate is lower atthe middle eastern region and gradually increased from the middle east to the north and south.(4) The standardized precipitation index (SPI), precipitation Z index and the relativewetting degree index M were calculated based on the typical stations selected：Huangzhong,HuaLong, Ledu and xunhua. Selecting suitable drought index for single station based oncomparing of three kinds of drought indexes characterize differences in intensity of droughtand drought frequency. The result is that M index can reflect the different characteristics ofdrought in different areas. And M index of typical years historical drought rating accuracyreached83.3%, this rating accuracy are much higher than SPI and Z index. In a word, themoist index M is a good monitoring for single station to occurrence, development and changelaws of drought.（5）Based on single station index relative wetting degree M index constructe a regionaldrought index R. Analysising of regional drought index R, the drought conditions reflected by regional drought index R is consistent to the data records of special historical drought yeardrought in Qinghai province.（6）Based on regional drought index analysis of regional drought evolution: averagemonthly area drought index of eastern agricultural Qinghai province has a linearly decreasingtrend in recent46years, drought trend ease. Spring and summer regional drought indexdecreased linearly, and autumn regional drought index increased linearly. The spring droughtlasted long and the intensity of the drought is great. Summer drought duration and intensity isrelatively smaller than spring drought. Autumn drought duration is same as summer drought,and drought intensity is bigger than summer, but it will not affect crop growth and production.Therefore, the main drought type at study area is spring drought and summer drought.Thistype of drought characteristics is mainly decided by the unique characteristic of the regionalclimate. Precipitation and evaporation are the main reason of more frequent seasonal droughtsin the eastern agricultural area of Qinghai province. From spatial distribution, the annual timescale of drought frequency and intensity are characterized by low south high north. Menyuanis the center of low value drought frequency and intensity in northern area, Xunhua is thecenter of high value drought frequency in southern area, and Guidei and Xunhua are thecenter of high value drought intensity in southern area. This kind of typical spatial distributionhas a lot to do with the distribution difference of rainfall and ET0in space.（7）Analysising the response of drought disaster to drought climate change in easternagricultural region of Qinghai province from the perspectives of both time and space.Form theperspectives of time, long time sequence and typical years all can see drought disaster is aresponse to drought climate change. Form the perspectives of space, region of droughtdisaster and drought climate space change had a very good corresponding relation, easternQinghai agricultural drought and drought climate changing has obviously temporal and spatialsynchronization. |
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