天山山区大气水分循环特征

将自然正交分解(EOF)和水平空间分辨率30"的地理信息数字高程(DEM)相结合,利用1961~2010年天山山区及其周边79个气象站月降水量应用梯度距离平方反比法计算面雨量,应用2000~2010年NCEP/NCAR逐日4次再分析1°(纬度)×1°(经度)资料计算水汽输送,研究了天山山区面雨量时空分布、水汽输送和外部水汽的降水转化率特征,以及降水转化率异常的初步成因。结果表明:1)天山西部和中部降水量平均在450 mm以上,东天山和天山西南端为150 mm左右。春季、夏季、秋季、冬季的面雨量分别为291.4×108 m3、625.9×108m3、218.1×108 m3和73.6×108m3,降水量分别为108.2 mm、232.4 mm、81.0 mm和27.4 mm,年降水量为449.0 mm。2)月水汽输送量呈正态单峰型分布,7月最大、1月最小,夏季水汽输送量为全年的41.3%,冬季为11.9%,春季、秋季分别为24.5%和22.3%。3)春季、夏季、秋季、冬季和年外部水汽的降水转化率分别为10.3%、12.6%、8.5%、5.4%和9.2%,降水转化率的大小与伊朗副热带高压、贝加尔湖高压脊和西亚副热带西风急流的位置和强度配置有关。

Characteristics of the Atmospheric Moisture Cycle over the Tian Shan Mountains

The temporal and spatial distribution of the Tian Shan mountains (TM) area precipitation, water vapor transport, the precipitation conversion rate from outer water vapor, the atmospheric moisture cycle and possible causes for the precipitation conversion rate anomaly over the TM was investigated by using monthly precipitation data from 79 observation stations in and around the TM and the NCEP/NCAR reanalysis daily dataset with 1°(latitude)×1°(longitude) horizontal resolution during 2000-2010. Results from the analysis show that: 1) The average precipitation is above 450 mm in the western and middle areas of the TM, but only about 150 mm in the eastern and southwesterly areas of TM. The total area precipitation in the spring, summer, autumn, and winter is 291.4, 625.9, 218.1, and 73.6×10⁸ m³, respectively, which, when converted to mm precipitation, is 108.2, 232.4, 81.0, and 27.4 mm. Annual precipitation is 449.0 mm. 2) The monthly water vapor transport shows a single-peak normal distribution, with a July maximum and a January minimum. Water vapor transport for spring, summer, autumn, and winter is 24.5%, 41.3%, 22.3%, and 11.9%, respectively. 3) The precipitation conversion rate for spring, summer, autumn, winter, and for one complete year is 10.3%, 12.6%, 8.5%, 5.4%, and 9.2%, respectively. The precipitation conversion rate is strongly related to the position and strength of the Iran high, Lake Baikal ridge, and the West Asia subtropical westerly jet stream, but is unrelated to water vapor input.