青藏高原“亚洲水塔”大气水分循环及其全球效应

Atmospheric Water Cycle over the Tibetan Plateau as the

  • 摘要: 青藏高原是世界上总辐射量最高的地区,也是全球超太阳常数的极值区域之一,故形成了一个“嵌入”对流层中部大气巨大的热源,并可一直伸展到自由大气,其超越了世界上任何超级城市群落所产生的“中空热岛”效应。青藏高原到黄土高原二阶梯大地形的“热力驱动”可作为“放大的海陆温差”季风效应,对区域乃至全球大气环流系统变化的动力“驱动”产生了难以估计的效应。青藏高原是亚洲区域低云量最为集中、对流活动最为活跃的地区,其特殊的湍流-对流触发机制为“亚洲水塔”云水资源提供了关键的能量驱动源。青藏高原特殊的“热驱动”及其“二阶梯型水泵”效应为源自低纬海洋乃至跨半球的水汽强“汇流”提供了动力机制。季风活跃期水汽输送“大三角扇形”关键影响域及其低纬热带海洋成为“亚洲水塔”大气水分循环的重要水汽源区,其水汽源区可跨越赤道追踪到南半球。夏季南、北半球跨赤道气流低层强偏南、高层强偏北气流出现在东亚地区(90°E)和北美区域(90°W)的赤道区,这两个高、低层跨赤道反向气流极值区恰与亚洲青藏高原和北美落基山位置相对应。从行星尺度环流特征的视角,印证了青藏高原、落基山不同高度的大地形对跨半球尺度的垂直纬圈、经圈环流的塑造作用,揭示出青藏高原与全球能量与水汽输送交换的重要“窗口效应”,表明青藏高原热源在驱动“亚洲水塔”能量、水分循环过程中扮演着重要的角色。研究发现,青藏高原对流活动与南极、北极水汽输送呈显著相关特征,凸显了“三极”的关联性。青藏高原上空热源驱动高层辐散、低层辐合的耦合机制,实现了青藏高原远距离的多尺度水汽输送强“汇合”效应,并形成了青藏高原热力驱动及其能量、水分循环“自激反馈”效应。“世界屋脊”上星罗棋布的冰川、积雪和湖泊储存着丰富的水环境资源,某种程度可起到“水塔存储池”效应。青藏高原与全球大气能量、水分循环过程具有重要的互反馈作用,这一陆地-海洋-冰冻圈大气能量与水分交换机制可描绘出一个系统的青藏高原与全球大气多圈层水分循环交互的图像。

     

    Abstract: Due to the fact that the Tibetan Plateau (TP) has the highest total radiation in the world and is one of the extreme regions of the global super solar constant, it has formed a huge heat source that is "embedded" in the central atmosphere of the troposphere and can extend to the free atmosphere, surpassing the "hollow heat island" effect produced by any supercity cluster in the world. The "thermal forcing" of the two-step terrain from the Tibetan Plateau to the Loess Plateau can serve as a monsoon effect from an "amplified sea-land temperature difference", which has an unpredictable effect on the dynamic "driving" of changes in regional and even global atmospheric circulation systems. The TP is featured with the highest concentration of low cloud cover and the most active convective activity in Asia. This special turbulence-convection triggering mechanism provides a key energy driving source for the cloud water resources of the "Asian Water Tower". The unique "thermal forcing" and "two-step water pump" effect of the TP provide a dynamic mechanism for the strong "convergence" of water vapor flows from low latitude oceans and even across hemispheres. During active monsoons, the key influence area of the "large triangular sector" water vapor transport in the low latitude tropical ocean have become important water vapor source areas for the atmospheric water cycle of the "Asian water tower", and the source areas can be traced across the equator to the southern hemisphere. In summer, the cross-equatorial airflow in the southern and northern hemispheres is characterized with lower-level southward flow and upper-level northward flow. They occur in the equatorial regions corresponding to two major terrains respectively: East Asia (90E) and North America (90W). The extreme value areas of these two cross-equatorial reversed airflows coincide with the positions of the TP in Asia and the Rocky Mountains in North America respectively. From the perspective of planetary-scale circulation characteristics, it also confirms that the topographic features of the TP and the Rocky Mountains at different heights are responsible for the construction of the vertically latitudinal and meridional circulations across the hemispheres. The study evidences the crucial "window effect" of the TP in global energy and water vapor transport, manifesting the key role of thermal forcing in the energy and water cycle processes of the TP, namely the "Asian water tower". Significant correlation of the convective activity over the TP to the global stratospheric water vapor transport in the Antarctic and Arctic is identified, highlighting the linkage of the "three poles". The coupling mechanism of high-level divergence and low-level convergence driven by the heat source over the TP leads to a strong "convergence" effect of multi-scale water vapor transport over long distances on the TP, forming the thermal forcing and the "self-excited feedback" effect of energy and water cycle on the TP. The glaciers, snow, and lakes scattered on the "Roof of the World" store abundant water resources, which can to some extent serve as a "water tower storage pool". The TP maintains an important mutual feedback effect with the global atmospheric energy and water cycle processes. This land-ocean-cryosphere atmospheric energy and water exchange mechanism can depict a systematic image of multi-layer water cycle between the TP and the Earth''s atmosphere.

     

/

返回文章
返回