The large-scale circulations and summer drought and wetness on the Tibetan plateau
The large-scale circulations and summer drought and wetness on the Tibetan plateau
复制标题
DOI：
10.1002/joc.1946
复制
发表时间：
2010-05-01
期刊：
影响因子：
--
通讯作者：
Zhu, Xiuhua
中科院分区：
文献类型：
--
作者：
Bothe, Oliver;Fraedrich, Klaus;Zhu, Xiuhua
利用ERA-40再分析资料和实测降水资料，分析了大尺度大气环流和地面温度对青藏高原夏季极端旱涝的影响。干旱和潮湿的极端情况可能与北大西洋/欧洲部分的环流异常和连接欧亚大陆的波列有关。西藏的干旱揭示了斯堪的纳维亚半岛上的强烈高压异常，并得到了北大西洋风暴路径的支持。这就产生了穿越欧亚大陆的波列，这些波列沿其向南的“大圆路线”到达东南亚，在那里它们通过一个反气旋气旋偶极子来调节青藏高原北部和东部的气流，抑制来自孟加拉湾的水汽供应。西藏的潮湿特征是一个更具有纬向性的跨大西洋风暴路径，在中欧上空产生一个低压异常，与此相关，副热带西风和热带东风急流向北移动;从北大西洋沿其赤道路线出现的波列现在有更大的机会到达副热带急流入口（而不是进一步向南传播）。然后波列再次加强，经过地中海阿拉伯海途径到达印度，与季风的西分支相互作用，为西藏提供充足的水汽供应。地面温度表明，在青藏高原极端和严重干旱（潮湿）的年份，会出现正（负）厄尔尼诺/南方涛动和印度洋偶极子事件。在高原干旱之前和伴随着高原干旱，在热带北大西洋出现明显的冷表面温度异常。版权所有（C）2009皇家气象学会
Effects of large-scale atmospheric circulation and surface temperatures on extreme dryness and wetness on the Tibetan plateau in summer are analysed using ERA-40 reanalysis and observed precipitation. The extreme cases of drought and wetness can be associated with circulation anomalies in the North Atlantic/European sector and wave trains bridging the Eurasian continent. Drought in Tibet reveals an intense high pressure anomaly over Scandinavia supported by a more south-west to north-east orientated North Atlantic stormtrack. This creates wave trains crossing Eurasia which, on their southward 'great circle route', reach south-eastern Asia where they modulate the flow north and east of the Tibetan plateau by an anticyclone cyclone dipole suppressing moisture supply from the Bay of Bengal.Wetness in Tibet is characterised by a more zonally oriented cross Atlantic stormtrack creating a low pressure anomaly over central Europe and, associated with it, a northward shift of the sub-tropical westerly and tropical easterly jet; wave trains emerging from the North Atlantic on their equatorward route have now a higher chance to reach the sub-tropical jet entrance (instead of propagating further south). Then the wave trains are re-intensified and, passing the Mediterranean Arabian Sea route to India, interact with the monsoon's western branch to lead to ample moisture supply for Tibet.Surface temperatures give indications for positive (negative) El Nino/Southern Oscillation and Indian Ocean Dipole episodes occurring in years of extreme and severe dryness (wetness) on the Tibetan plateau. A pronounced cold surface temperature anomaly in the tropical North Atlantic precedes and accompanies drought on the plateau. Copyright (C) 2009 Royal Meteorological Society