我国东、西部夏季水汽输送特征及其差异

本文利用ERA-40再分析每日资料分析了我国东部季风区与西北干旱—半干旱区夏季1971～2000年气候平均的水汽输送特征及其差异, 分析结果表明我国东部季风区与西北干旱—半干旱区夏季气候平均的水汽输送特征有明显的差异。由于亚洲夏季风从孟加拉湾、 南海和热带西太平洋输送大量水汽到我国东部季风区, 故在东部季风区夏季经向水汽输送通量比纬向水汽输送通量大。而西北干旱—半干旱区受中纬度西风带的影响, 夏季纬向水汽输送通量比经向水汽输送通量大, 且此区域夏季无论纬向或者经向水汽输送通量均比东部季风区的水汽输送通量小一量级。并且, 分析结果还表明: 我国东部季风区由于湿度大, 故夏季水汽输送通量的散度不仅依赖于湿度平流, 而且依赖于风场的辐合、 辐散, 而西北干旱—半干旱区夏季水汽输送通量的散度主要依赖于湿度平流。此外, 分析结果还表明了我国东部季风区的水分平衡与西北干旱—半干旱区的水分平衡也有明显的不同。

Characteristics of the Summertime Water Vapor Transports over the Eastern Part of China and Those over the Western Part of China and Their Difference

Characteristics of the climatological mean summertime water vapor transports for 1971-2000 over the monsoon region of eastern China and those over the arid and semi-arid regions of Northeast China and their differences are analyzed by using the daily data of the ERA-40 reanalysis. The results show that there are some obvious differences between the summertime water vapor transports over the monsoon region of East China and those over the arid and semi-arid regions of Northwest China. Since a large amount of water vapor is transported by the Asian summer monsoon flow from the Bay of Bengal, the South China Sea, and the tropical western Pacific into the monsoon region of eastern China, the meridional water vapor transport fluxes are larger than the zonal water vapor transport fluxes in the monsoon region of eastern China in summer. But influenced by the westerly zone over mid-latitudes, the summertime zonal water vapor transport fluxes are larger than the meridional water vapor transport fluxes in the arid and semi-arid regions of Northwest China, and either zonal or meridional water vapor transport fluxes in the region are one order of magnitude smaller than those in the monsoon region of East China. Moreover, the results show that the divergence of the summertime water vapor transport fluxes in the monsoon region of East China depends on not only the moisture advection, but also the convergence or divergence of wind field over this region, but it mainly depends on the moisture advection in the arid and semi-arid regions of Northwest China. Besides, the results also show that the water balance in the monsoon region of eastern China is obviously different from that in the arid and semi-arid regions of Northwest China. 