用西北地区140个气象站1971～2000年的春季降水、蒸发资料,计算了一种K干旱指数,并制定了干旱标准,分析了西北春季干旱的气候特征。对K干旱指数与改进的Palmer干旱指数、降水距平百分率干旱指数作了比较分析;同时利用没有参加干旱指标划分的2001～2005年乌鲁木齐、玉树、兰州和西峰4个代表站(分别代表干旱、高原、半干旱和半湿润地区)的降水、蒸发独立样本资料对制定的干旱指标进行了检验。结果表明,新疆南部、甘肃西部、青海西部是重旱的高发区;新疆北部偏南地区、甘肃北部、南部和东部、宁夏北部、青海东南部、陕西北部是中旱的高发区;新疆西部、甘肃南部、青海西部、陕西东部是轻旱的高发区。K干旱指数对西北春季干旱有较好的监测能力;改进的Palmer干旱指数对干旱区的干旱监测效果好,但对高原、半干旱、半湿润地区的干旱监测有一定的局限;降水距平百分率干旱指数对轻旱和重旱监测效果好,对中旱监测能力差。在2001～2005年的检验中,再次证明改进的Palmer干旱指数对西北地区干旱监测有一定的局限,K干旱指数对西北地区的干旱监测有较好的效果。

A kind of K drought index and its criterion are made by using spring precipitation and evaporation data of 140 stations in Northwest China from 1971-2000.At the same time,the comparison is done among the defined K drought index,improved Palmer drought index and precipitation anomaly percent. From 2001 to 2005,the verifications of K drought index have done with the independent precipitation and evaporation data,which were not involved in making the drought criterion at four representative stations,namely Urumqi,Yushu,Lanzhou and Xifeng,respectively.The results show that the heavy drought areas are located in south Xinjiang,west Gansu and west Qinghai,the moderate drought areas are located in southern part of north Xinjiang,north and east Gansu,north Ningxia,southeast Qinghai and north Shaanxi,and the light drought areas are located in west Xinjiang,south Gansu,west Qinghai and east Shaanxi.The K drought index has a better function of drought monitoring,and the improved Palmer drought severity index has better monitoring effect in arid area,but it has some limitations to monitor drought in plateau area,semi-arid and sub-humid areas.Precipitation anomaly percent has good monitoring effect for light and heavy drought,but it has bad monitoring effect for moderate drought.It is verified again from 2001 to 2005 that the improved Palmer drought severity index has some limitations to monitor drought in Northwest China,but the K drought index has better monitoring effect in Northwest China.