HOW DO ATMOSPHERIC RIVERS FORM?
HOW DO ATMOSPHERIC RIVERS FORM?
复制标题
DOI：
10.1175/bams-d-14-00031.1
复制
发表时间：
2015-08-01
影响因子：
8
通讯作者：
Lavers, D. A.
中科院分区：
文献类型：
--
作者：
Dacre, H. F.;Clark, P. A.;Lavers, D. A.
大气河流一词用来描述对流层中强烈水汽输送的走廊。从亚热带延伸到温带的卫星图像中常见的增强水汽细丝，通常被用作识别这些强水汽输送区域的指标。与这些水蒸气增强的细丝有关的降水可能会导致高影响的洪水事件。然而，关于这些细丝是如何形成的，仍然存在一些争议。本文分析了冬季北大西洋温带气旋气候学中的水汽输送。结果表明，大气河流是由冷锋追赶暖锋时卷起暖区水汽形成的。这导致在温暖的传送带气流底部的冷锋前方形成一条高水汽含量的窄带。因此，气旋暖区的水汽，而不是来自亚热带的水蒸气的长距离输送，是产生高水汽含量的细丝的原因。气旋内的蒸发和水汽汇聚的连续循环补充了通过降水失去的水蒸气。因此，这些细丝并不代表从亚热带向气旋中心的湿空气的直接和连续输送(如术语大气河流所暗示的)，事实上，这些细丝是气旋输出的水蒸气的结果，因此它们代表了气旋从亚热带向极地移动时留下的足迹。
The term atmospheric river is used to describe corridors of strong water vapor transport in the troposphere. Filaments of enhanced water vapor, commonly observed in satellite imagery extending from the subtropics to the extratropics, are routinely used as a proxy for identifying these regions of strong water vapor transport. The precipitation associated with these filaments of enhanced water vapor can lead to high-impact flooding events. However, there remains some debate as to how these filaments form. In this paper, the authors analyze the transport of water vapor within a climatology of wintertime North Atlantic extratropical cyclones. Results show that atmospheric rivers are formed by the cold front that sweeps up water vapor in the warm sector as it catches up with the warm front. This causes a narrow band of high water vapor content to form ahead of the cold front at the base of the warm conveyor belt airflow. Thus, water vapor in the cyclone's warm sector, not long-distance transport of water vapor from the subtropics, is responsible for the generation of filaments of high water vapor content. A continuous cycle of evaporation and moisture convergence within the cyclone replenishes water vapor lost via precipitation. Thus, rather than representing a direct and continuous feed of moist air from the subtropics into the center of a cyclone (as suggested by the term atmospheric river), these filaments are, in fact, the result of water vapor exported from the cyclone, and thus they represent the footprints left behind as cyclones travel poleward from the subtropics.