Drought Changes In Inner Mongolia In Last60Years

Inner Mongolia (97°12’E-126°04’E,37°24’ N-53°23’N) in the hinterland ofEurasia, which spans large from north to south and extends long from east to west is atypical monsoon’s boundary area. Winter climate here, under the influence of Siberia-Mongolia high, is characterized by dry and cold. while in summer its hot and rainy,rain in hot season, by the effect of East Asian summer monsoon. And the amount ofprecipitation in this region is controlled by the outbreak of the time, intensity andduration of the summer monsoon. Therefore, the inter-annual changes in precipitationis intense, regional difference is obviously, and the spatial and temporal distribution isvery uneven. And under the great background of global warming, Inner Mongolia hasbecome the region where the droughts have the most frequent occurred, the mostwidely distributed and the greatest influenced, receives great concern to all levels ofgovernment and academia. Drought induced shortage of water resources and lead toserious ecological and environmental problems, resulting in huge economic losses andthe constraints and limitations of regional economic and social sustainabledevelopment in the region.In order to make a deeper understanding of the dynamic process of aridity inInner Mongolia, the monthly observations of94meteorological stations in this regionand its surrounding were used and five Drought Index were selected, the droughtconditions of60a in the study area were comprehensively analyzed, and combinedwith the comparative analysis and empirical analysis of various drought index,evaluated the sensitivity of the drought index, indicated the applicability of droughtindex in the area, and thus accurate understanding of the Inner Mongolia aridcharacteristics, regular cycle, then providing a scientific basis for our region anddrought relief work ultimately. The main conclusions are as follows:1. According to the actual situation of shorter observation time, caliber differenceand the uneven distribution of some meteorological stations in Inner Mongolia, thetime series were improved by the use of least squares interpolation of meteorologicaldata. Thiessen polygon method and spline interpolation method were used for calculating the site proportion and spatial differences in the area, and to establish aregional scale drought temporal evolution pattern;2. Selected the precipitation anomaly percentage (Pa), the SPI Index, the S-indexZ-index and K index for calculating the arid evolution of seasonal, inter-annual anddecadal scales in Inner Mongolia during the60a. The results showed that the fivedrought indexes have reflected the general trend of the drought and the temporal andspatial scales of drought occurrence in the study area very well. However, the physicalsignificance, the mechanism of the mechanism and the emphasis of the indexes aredifferent, so there are some differences in the temporal and spatial evolution of thedrought in this region.3. The SPI Index showed that there was drought of nine years out of ten in InnerMongolia, which presented as drought of six years out of ten in1950s, drought of nineyears out of ten in1960s and rose to drought of ten years out of ten in1970s and1980s. Although there was a drought occurrence downward trend in1990s whichshowed drought of seven years out of ten, there was drought of nine years out of tenfrom2001to2010. The S index also showed the characteristics of drought of nineyears out of ten, and its mainly concentrated in the period from the mid-1980s to thepresent; The number of drought occurrence extracted by the Z index and the Pa in thetime scale is less, there were46and35years of drought respectively in the studyperiod; The number of drought occurrence extracted by the K index from1960to2008were30years, accounting for61%of the time series, it’s the second only to theSPI (68%).4. In the regional scale, the highest frequency droughts were Alashan, Ordos andLinhe in western Inner Mongolia, which were mainly moderate drought, even severedrought. Then the higher frequency droughts were Hohhot, Baotou, Wulanchabu andXilinGol League in the middle of Inner Mongolia. The four Cities from the Easternpart had the least occurrences of disaster, and the drought intensity was lighter.5. By comparing, the time series and the spatial distribution of drought from theSPI index were the most similar to Inner Mongolia’s, which sensitively reflected thedrought occurrence and development situation of the study region, making the SPIindex the most useful index. S index shown a good consistent on the drought time scale with Inner Mongolia’s, which is better than Pa and Z index, but the sensitivity tothe spatial distribution is poor, arid center is blurred, the indicating range is either toolarge or too small and there is a big difference in empirical analysis. Z index reflectedthe spatial distribution of the drought very well, and consistent with the actual droughtbetter than the S index and Pa. But to the time series, the number of detected droughtis small, and there are differences between the actual drought and the Z index. Thenumber of drought by K index is larger, only after the SPI index, indicated a verysimilar drought intensity to the actual one, is superior to other drought index, makingit a very useful index. Pa index shows the least number of droughts, level is weak,does not reflect the facts of the Inner Mongolia arid, is different with the actualsituation. Shown a smaller range on drought distribution, which is different from theactual situation.