黑河流域水汽输送及收支特征

利用NCEP/NCAR逐日再分析资料对黑河流域的水汽输送和收支特征进行了计算分析,结果表明:西风环流使得源于大西洋和北冰洋的水汽成为黑河流域空中水汽的主要来源,流域内水汽输送以自西向东的纬向输送为主,东边界输出强度强于西边界输入强度,纬向净输入量为负;经向输送为自北向南且在强度上不及纬向输送,北边界输入强度强于南边界输出强度,经向净输入量为正。700 hPa气层流域南部的水汽辐合辐散特征随季节变化显著,冬季为水汽辐散区,夏季为水汽辐合区;流域北部没有明显的水汽辐合辐散特征。全流域多年平均水汽输入量为997.3 km³,输出量为1 046.1 km³,净输入量-48.8 km³,20世纪60年代中期以后流域水汽净输入量呈现增加趋势。黑河流域北部荒漠区年内各季均为水汽输出期,中低层大气(地面~500 hPa)为主要的水汽输出层;南部山区年内6-9月为水汽输入期,低层大气(地面~700 hPa)为水汽输入层,中高层大气(700~300 hPa)为水汽输出层。据大气水平衡原理,黑河流域多年平均蒸发量约为84 km³。

Characteristics of Water Vapor Transportation and Budget over the Heihe Drainage Basin

Based on the NCEP/NCAR re-analysis daily mean data from 1948 to 2008,the characteristics of water vapor transportation and budget over the Heihe Drainage Basin were analyzed in this passage.The results showed that,influenced by westerly circulation,Atlantic and Arctic oceans were the main water vapor source over the Heihe Drainage Basin.Water vapor was mainly latitudinally transported from west to east,and the intensity of water vapor exported from east boundary of the Heihe Drainage Basin was greater than that imported from west boundary,the intensity of water vapor imported from north boundary was also greater than that exported from south boundary.In the layer of 700 hPa,convergence and divergence of the southern Heihe Drainage Basin changed seasonally,it is a water vapor divergence area in winter,but a convergence area in summer.The northern Heihe Drainage Basin had no such obvious characteristics all the year round.The annual influent water vapor amount is about 997.3 km3,effluent water vapor amount is about 1046.1 km3,and the net water vapor amount is about 48.8 km3.The net water vapor amount tended to increase since the 1960s.Water vapor in the northern desert area of the Heihe Drainage Basin exported whole year,and it mainly exported from middle and lower atmosphere(surface to 500 hPa).June to September was the water vapor net influent period in the southern mountain area of the Heihe Drainage Basin,and lower atmosphere(surface to 700 hPa) was the main influent layer,middle and upper atmosphere(700 to 300 hPa) was the main enffuent layer.Annual evaporation amount is about 84 km3 according to the atmospheric water balance.