西北干旱区阿勒泰地区暖季干旱指数及干旱分析

Drought index and analysis for the warmer season in Northwest arid area of Altay region

干旱是限制阿勒泰地区农牧业生产可持续发展最主要的自然灾害之一,干旱指数研究是进行有效干旱监测的基础。利用阿勒泰地区7个气象站1961-2008年暖季4-10月月平均气温、降水量资料,首先通过Thomthwaite方法计算潜在蒸发量,定义了干旱指数K。分析了该地区降水和潜在蒸发、干旱的时空分布特征,选取降水距平和Z干旱指数与K指数的干湿等级进行比较,结果表明:夏秋季降水量分布相对较均,春季差异较大,最多是最少的2倍;夏季降水较多,是春秋季的2倍左右。春夏季潜在蒸发与降水分布基本相反,但秋季最大潜在蒸发与降水最大值的分布一致。用降水变率比潜在蒸发变率定义的干旱指数反映了阿勒泰地区干旱频率在50%以上,暖季富蕴站干旱最重;就各季而言,夏季干旱相对较重,春季相对较轻;在空间分布上,春季布尔津、夏季富蕴、秋季青河站干旱相对较重。对降水量距平百分率和Z干旱指数、K指数的比较检验表明,K指数优于R指数和Z指数,对暖季干湿状况的确定更客观,更符合实际。

Drought is one of the uppermost natural disasters that limit the sustainable development of farming and animal raising in Altay,and drought index research is the foundation for the effective drought monitoring.The average temperature and precipitation data were obtained from seven weather stations of Altay in each month during the annual warm-season（April to October） from 1961 to 2008,and the Thomthwaite method was used to definite the drought index K by calculating the potential evaporate quantity;and then the regional precipitation,the potential evaporation,and the temporal and spatial distribution of drought were analyzed;Finally,we compared the wet and dry level by the precipitation anomaly,the Z drought index and the K drought index.The results showed that： in summer and autumn,the rainfall was relatively uniform,but it was quite different in spring,the maximum rainfall was more than two times to the minimum rainfall;there was more precipitation in summer,and it was about two times compared to the spring and autumn.In the spring and summer,the potential evaporation was opposite to the precipitation distribution,however,in the autumn,the greatest potential evaporation was consistent to the maximum precipitation distribution.The drought index was calculated by using the change rate of the precipitation to divide the change rate of the potential evaporation,and it reflected that the drought frequency in the Altay region was more than 50%,the Fuyun station was the heaviest drought place in the warm-season;for each season,the drought in the summer was relatively heavy,and it was relatively lighter in the spring;in spatial distribution,the drought in the Burqin,Fuyun and Green River station was relatively heavy respectively in the spring,summer and autumn.Comparison of the precipitation anomaly percentage,Z drought index and K index showed that the K index was superior to the R index and Z index,and the K index was more objective and more realistic to fix the wet and dry conditions in the warm-season.