Responses and impacts of atmospheric rivers to climate change

March 24, 2020

In March 2020 the most substantial review article to date focusing on atmospheric rivers (AR) was published in the first volume of the new journal Nature Reviews: Earth and Environment. The article, led by Ashley Payne (Univ. of Michigan) focuses on climate change dimensions, and was prepared by an international group of scientists, including Scripps/CW3E’s Director, F. Martin Ralph. It provides a useful synopsis of existing literature on ARs, citing over 180 articles. The paper establishes a basic framework for looking at climate change impacts as a combination of sometimes offsetting thermodynamic (moistening of the atmosphere due to warming) and dynamic (e.g., shifting extratropical storms tracks) physical processes. It also addresses impacts of ARs on the hydrological cycle and on hydrologic extremes. The review is summarized schematically in the attached figure that illustrates projected trends in AR counts/locations and their impacts globally, from precipitation and flooding to snow/ice melt.

Finally, the paper identifies key new directions in AR research, ranging from the need for higher resolution modeling, better observations (especially of regions globally where they are lacking), the importance of ARs in polar change, and ultimately of impacts of ARs through their roles in extreme events and in providing beneficial water supply.

Figure 1: Projected changes and impacts in atmospheric rivers. Summary schematic of the main changes to atmospheric-river (AR) characteristics and impacts under warming. Red and blue symbols reveal increases and decreases, respectively; for frequency, red refers to a poleward movement and blue an equatorward movement of landfall. Light red and blue symbols with ‘?’ indicate uncertainty in the projection. Grey symbols indicate unknown changes. Background shading illustrating AR frequency increases is based on Espinoza et al.¹⁰⁷. Figure 2 of Payne et al. (2020).

Payne, A.E., M. Demory, L.R. Leung, A.M. Ramos, C.A. Shields, J.J. Rutz., N. Siler, G. Villarini, A. Hall, F.M. Ralph. Responses and impacts of atmospheric rivers to climate change. Nat Rev Earth Environ 1, 143–157 (2020). https://doi.org/10.1038/s43017-020-0030-5