Air–sea interaction and formation of the Asian summer monsoon onset vortex over the Bay of Bengal
Air–sea interaction and formation of the Asian summer monsoon onset vortex over the Bay of Bengal
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DOI：
10.1007/s00382-010-0978-9
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发表时间：
2011
期刊：
影响因子：
4.6
通讯作者：
Guoxiong Wu;Y. Guan;Yimin Liu;Jinghui Yan;J. Mao
中科院分区：
文献类型：
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作者：
Guoxiong Wu;Y. Guan;Yimin Liu;Jinghui Yan;J. Mao
在孟加拉湾南部（BOB）的春季，一个涡旋通常发展，其次是亚洲夏季风爆发。对相关资料的分析和个例分析表明，春季BOB季风爆发涡是BOB海气相互作用的结果，并受到青藏高原强迫和南亚地区海陆热力对比的调制。春季青藏高原强迫在对流层低层印度上空产生一个盛行的冷西北风。强烈的地面感热释放，形成一个突出的地面气旋，并沿沿着洋面形成强烈的西南风。这股西南风引起了当地的离岸流和上升流，导致了寒冷的海面温度（SST）。西南风与近赤道西风共同作用，也导致BOB大部分地区上空形成一个地面反气旋，空气下降，BOB南部上空形成一个气旋，空气上升。在BOB中部的东部，由于天空晴朗，地面风弱，海洋混合层较浅，强烈的太阳辐射和较弱的地面潜热和感热通量导致的低能量损失作用于薄的海洋层上，导致春季BOB暖池的发展。在近地面，水汽从北方BOB和其他地区输送到BOB东南部，那里的地面感热相对较高。产生大气可用势能并将其转换为动能，从而导致涡旋形成。低涡增强并向北移动，在那里SST较高，地面感热较强。同时，纬向平均动能在低涡以东地区转化为涡动动能，低涡转向东移。最后，西南气流扫过东孟加拉国，并与副热带西风合并，导致亚洲夏季风的爆发。
In spring over the southern Bay of Bengal (BOB), a vortex commonly develops, followed by the Asian summer monsoon onset. An analysis of relevant data and a case study reveals that the BOB monsoon onset vortex is formed as a consequence of air–sea interaction over BOB, which is modulated by Tibetan Plateau forcing and the land–sea thermal contrast over the South Asian area during the spring season. Tibetan Plateau forcing in spring generates a prevailing cold northwesterly over India in the lower troposphere. Strong surface sensible heating is then released, forming a prominent surface cyclone with a strong southwesterly along the coastal ocean in northwestern BOB. This southwesterly induces a local offshore current and upwelling, resulting in cold sea surface temperatures (SSTs). The southwesterly, together with the near-equatorial westerly, also results in a surface anticyclone with descending air over most of BOB and a cyclone with ascending air over the southern part of BOB. In the eastern part of central BOB, where sky is clear, surface wind is weak, and ocean mixed layer is shallow, intense solar radiation and low energy loss due to weak surface latent and sensible heat fluxes act onto a thin ocean layer, resulting in the development of a unique BOB warm pool in spring. Near the surface, water vapor is transferred from northern BOB and other regions to southeastern BOB, where surface sensible heating is relatively high. The atmospheric available potential energy is generated and converted to kinetic energy, thereby resulting in vortex formation. The vortex then intensifies and moves northward, where SST is higher and surface sensible heating is stronger. Meanwhile, the zonal-mean kinetic energy is converted to eddy kinetic energy in the area east of the vortex, and the vortex turns eastward. Eventually, southwesterly sweeps over eastern BOB and merges with the subtropical westerly, leading to the onset of the Asian summer monsoon.