东亚地区水汽输送强、弱年水汽输送的异同

The Differences and sames of vapor transportation between strong vapor transportation year and weak one in the East-Asia

  • 摘要: 利用1950—2002年NCAR/NCEP再分析逐日平均资料,计算全球格点整层水汽输送通量,分析东亚地区水汽输送强、弱年候平均水汽输送的异同点。水汽输送强、弱年都存在一条行星尺度水汽输送带,但是又有显著的差异:(1) 南半球越赤道、阿拉伯海、孟加拉湾的水汽输出量不同。(2) 副热带高压外围水汽的强度和影响范围不同。(3) 中纬度向内蒙古中部和东北地区输送水汽的偏西风水汽输送带在水汽输送强年明显、弱年不明显。(4) 在水汽输送强年中国云贵高原—长江中游—华北—东北南部有一条明显的水汽输送大值带,中国中、东部均有水汽输送,只是中国东南部和长江中下游地区水汽输送相对较少;在水汽输送弱年仅中国南方、东部沿海和东北地区南部有弱的水汽输送。(5) 水汽输送强年的变化较为平缓,而水汽输送弱年则比较迅速。东亚地区偏南风水汽输送在水汽输送强、弱年的相同特征是:特征线南撤的速度非常快,在20°—30°N 附近有东南风水汽输送加入,并取代西南风水汽输送;不同之处是,水汽输送强年建立的时间早、能够到达更北的纬度、强盛期长、撤退的时间迟。副热带高压南侧东南风水汽输送在水汽输送强、弱年的共同点是,西界均为95°E,由建立到强盛的速度都非常快,在强盛期突然就东撤到130°E以东的区域;不同点是,在160°E处东南风水汽输送建立的时间不同,强盛期不同,到达西界的时间不同,印度季风槽在95°E以西形成的东南风水汽输送持续时间和影响范围不同,西扩和东撤的速度不同。

     

    Abstract: By use of the NCEP/NCAR daily mean reanalysis data from 1950 to 2002, vertically integrated moisture fluxes (VIMFs) were calculated over East Asia, and a strong/weak moisture transport year (SMTY/WMTY) was defined according the coefficient of the first EEOF eigenvector of pentad mean VIMFs of the summer half-year (April-September) for the period 1950-2002. Similarities and differences of pentad mean VIMFs between SMTYs and WMTYs are studied through examination of the spatial distributions of mean moisture transport, seasonal advance of southerly wind moisture transport (SMT), and the intensity and evolution of the southeast wind moisture transport (SEMT) south of the Northwest Pacific subtropical high. The results show that:1) In SMTYs, the northward transport of VIMFs across the Equator from the Southern Hemisphere to the Northern Hemisphere, and the northeastward transport of VIMFs over the Arab Sea and the Bay of Bengal are significntly large, the westerly wind moisture transport belt in the mid-latitudes (40°-45°N) over East Asia is remarkable, and changes in moisture transport in the summer half-year are relatively small. However, in WMTYs, the opposite is true. Furthermore, there is a large VIMF belt over the Yunnan-Guizhou Plateau, the midreach of the Yangtze River, North China, and the southern part of Northeast China in SMTYs, but in WMTYs, there is only a small VIMFs belt over southern China,the east coast region, and the southern part of Northeast China. 2) The SMT in East Asia (100°-130°E) starts earlier in SMTYs, it reaches a higher latitude and prevails for a longer period of time, and retreats southwards at a later date in comparison with that in WMTYs. 3) The onset of SEMT at 160°E in SMTYs is earlier, the SEMT lasts longer, and reaches its western limit (95°E) later relative to the transport in WMTYs; and the SEMT west of 95°E in the south of Himalaya Mountains associated with the Indian monsoon trough has a longer duration and a larger influencing region in SMTYs than in WMTYs.

     

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