Ong Hing, Yang Da
Argonne National Laboratory, Lemont, IL, USA.
University of Chicago, Chicago, IL, USA.
Nat Commun. 2024 Nov 4;15(1):9428. doi: 10.1038/s41467-024-53369-0.
Poleward water vapor transport in the midlatitudes mainly occurs in meandering filaments of intense water vapor transport, spanning thousands of kilometers long and hundreds of kilometers wide and moving eastward. The water vapor filaments are known as atmospheric rivers (ARs). They can cause extreme wind gusts, intense precipitation, and flooding along densely populated coastal regions. Many recent studies about ARs focused on the statistical analyses of ARs, but a process-level understanding of ARs remains elusive. Here we show that ARs are streams of air with enhanced vapor kinetic energy (VKE) and derive a governing equation for Integrated VKE to understand what contributes to the evolution of ARs. We find that ARs grow mainly because of potential energy conversion to kinetic energy, decay largely owing to condensation and turbulence, and the eastward movement is primarily due to horizontal advection of VKE. Our VKE framework complements the integrated vapor transport framework, which is popular for identifying ARs but lacks a prognostic equation for understanding the physical processes.
中纬度地区向极地的水汽输送主要发生在强烈水汽输送的蜿蜒细丝中，这些细丝长达数千公里，宽数百公里，并向东移动。水汽细丝被称为大气河流（ARs）。它们会在人口密集的沿海地区引发极端阵风、强降水和洪水。最近许多关于大气河流的研究都集中在对大气河流的统计分析上，但对大气河流在过程层面的理解仍然难以捉摸。在这里，我们表明大气河流是具有增强水汽动能（VKE）的气流，并推导了积分水汽动能的控制方程，以了解是什么因素导致了大气河流的演变。我们发现，大气河流的增长主要是由于势能转化为动能，其衰减主要是由于凝结和湍流，而向东移动主要是由于水汽动能的水平平流。我们的水汽动能框架补充了积分水汽输送框架，后者在识别大气河流方面很受欢迎，但缺乏用于理解物理过程的预测方程。
