全球水循环的海洋分量研究

利用ＮＣＥＰ／ＮＣＡＲ再分析月平均和逐日资料，采用“余差”方法，计算了１９８４～１９９４年全球海气淡水通量，分析了全球水汽输送的特点。主要结果有：（１）在全球水循环中，副热带大洋是重要的水汽辐散区，热带辐合带、南太平洋辐合带和南太平洋东南海域是集中的水汽辐合区，赤道东风带是夏季印度洋季风环流的主要水汽通道；（２）再现了全球海气淡水通量的分布，例如副热带“海洋沙漠”带、热带辐合带和南太平洋辐合带净降水区等；展示了细节特征，如黑潮区的净蒸发特点等；（３）发现了北大西洋中高纬度地区存在一东北—西南向的净蒸发带，而前人结果中则为净降水带；（４）分析了各大洋海气淡水通量的季节、年际变化特征，讨论了太平洋相对于大西洋作为水汽汇的特点；指出热带辐合带和南太平洋辐合带是海气淡水通量变率最大的海域

THE AIR-SEA FRESHWATER EXCHANGE DERIVED FROM NCEP/NCAR REANALYSIS DATA

For the period from 1984 to 1994, the aspects of annual and monthly distributions of air sea freshwater exchange over global ocean derived from the NCEP/NCAR monthly and daily reanalysis data are studied.The results show that the subtropical oceans act as important moisture sources, while Intertropical Convergence Zone(ITCZ), South Pacific Convergence Zone(SPCZ) and southeast part of South Pacific serve as vapor sinks in global water cycle. Equatorial easterlies plays an important role in providing water vapor for Indian monsoon circulation. Some typical realistic features of global air sea freshwater flux are reproduced in current study, such as the midlatitude rain belt, the strong subtropical dry belt, the ITCZ and SPCZ rain belts. Furthermore, some new features have seen shown, a case in point is the prominent region of net water loss in the North Pacific near the Kuroshio. Both ITCZ and SPCZ are found to be the regions with strong variance. It should be pointed out that in extratropical and subpolar regions of North Atlantic, where precipitation dominates in former studies, a belt of net water loss trending from northeast to southwest is found for the first time and the inside reason may lie in that the transient component of freshwater flux was ignored in former studies, since only monthly data were provided and used in former evaluation. The analysis on seasonal and annual variations of global air sea freshwater exchange show that the Atlantic Ocean is more drier than the Pacific Ocean as a whole.