西北地区秋季干旱指数的变化特征

利用甘肃、宁夏、青海、新疆4省(区)的137个气象站30年的降水、蒸发资料,确定适合西北地区的干旱指数计算方法,分析中国西北地区秋季降水、蒸发、干旱指数的空间分布、时间演变等特征.结果表明:西北地区秋季平均自然降水从东南到西北依次减少,在甘肃西部、青海西北部、新疆南部有一条东西向的少雨带,是干旱最严重的地方.新疆南部、甘肃西部、青海西部重旱频率最高,平均2年一遇;新疆北部、甘肃南部、青海南部、中旱频率为30%左右,平均3年一遇,轻旱频率30%左右,平均3年一遇.表明西北地区的干旱有明显的地域特征,即新疆中南部、甘肃西部、青海西部为干旱区,新疆北部、甘肃中东部、青海东部和南部为半干旱区.

Analysis on the Change of Aridity Index in Northwest China in Autumn

Based on the precipitation and evaporation data observed by 137 meteorological stations in Gansu Province, Ningxia Hui Autonomous Region, Qinghai Province and Xinjiang Uygur Autonomous Region in recent 30 years, in this paper the method of calculating the aridity index in northwest China is determined, and the spatial distribution and temporal evolution of precipitation, evaporation and aridity index in northwest China in autumn are analyzed. The results show that the precipitation in northwest China decreases from the southeast to the northwest, there is a zone with infrequent occurrence of precipitation from west Gansu Province, north- west Qinghai Province and south Xinjiang, where drought is the most serious, and the aridity index can be used to objectively reveal the drought situation in northwest China. The occurring frequency of serious drought is the highest in south Xinjiang, west Gansu Province and west Qinghai Province, and the serious drought occurs once every 2 years in average; the occurring frequency of both mid-drought and slight drought is about 30% in north Xinjiang, south Gansu Province, south Qinghai Province and the most regions of Shaanxi Province, and the mid-drought and slight drought occur every 3 years in average. These reveal that the drought in northwest China is obviously regional, that is central and south Xinjiang, west Gansu Province and west Qinghai Province are the arid areas, north Xinjiang, central and east Gansu Province, east Qinghai Province and north Shaanxi Province are the semiarid areas, and south Shaanxi Province is a humid area.