中文摘要：

用1948--2009年NCEP／NCAR月平均再分析资料，分析低纬高原地区对流层不同层次水汽输送特征。结果表明，地面～300hPa每年从西边界、南边界流入低纬高原的水汽分别有344．O×10^10t和115．O×10^10t，有341．5x10^10t和73．5×10^10t水汽分别从东边界和北边界流出，水汽净流入达44．0×10加t。水汽净收入主要集中在对流层低层，以西边界的水汽输入最多；但经向上的水汽输送对低纬高原地区的净收入贡献相对较大，并且纬向水汽输送与经向水汽输送量呈反相关。夏季水汽输送净收入占全年的67．5％，其对流层低、中、高层均为水汽净流人。西边界水汽输入呈增加趋势，东边界水汽输出量呈减少趋势，南、北边界水汽输入、输出呈减少趋势，均在1980年代末发生突变，突变后南边界的水汽输入明显减少，北边界的输出呈下降趋势。年净水汽和夏季净水汽呈减少趋势。低纬高原地区水汽净收入在1978年发生突变，突变后水汽呈减少趋势。

英文摘要：

Based on the monthly NCEP/NCAR reanalysis data from 1948 to 2009, the features of water vapor transport for different layers of the troposphere over low latitude plateau area are analyzed. The results show that the integrated water vapor inflow from surface to 300hPa, where takes place from the western and southern boundary of the area, is 344.0x 101~t and 115.0x 101~t per annum, while the integrated water vapor outflow, where occurs in the eastem and northern boundary, is 341.5x 101~t and 73.5x101~t per annum. So the net water vapor input is 44.0x101~ t per annum. The net water vapor inflow is mainly in the lower troposphere（western boundary is the most）, but the meridional water vapor transportation make greater contribution for this area. Meanwhile there is an anti-correlation between the meridional and the zonal water vapor transportation. In summer, the net income of water vapor transportation account for 67.5% of all year, each layer of troposphere is net inflow. The yearly water vapor inflow shows an increasing trend in the western boundary and an outflow decreasing trend in the eastern boundary, in and out flow represent decreasing trend in the southern and northern boundaries. All of these conditions change abruptly in the late 1970s, the water vapor inflow from the southern boundary and outflow from the northern boundary decrease after the period （inflow from the southern boundary is significant）. Therefore, the trend of net water vapor decrease in summer and all year. The net water vapor inflow is abrupt change in 1978.The trend of water vapor decrease after the year of abrupt change.