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Atmospherice rivers

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Atmospheric river associated with storm Lothar after Christmas 1999. Left analyzed from ERA-interim data. Right: downscaled with a regional high resolution climate model Shown is the vertically integrated atmospheric moisture transport

Atmospheric rivers can drive hazardous precipitation often paralleled by intense flooding. Studies from the global CMIP5, and CMIP6 suite clearly indicate that the risk for AR induced precipitation will increase in a future warmer climate.This result is in accordance with the expexted thermodynamical response to climate warming. For the local pattern of heavey precipitation, however, dynamical changes, such as systematic changes in the routing of atmospheric rivers over the continent represent an additional source of uncertainty at the local scale.

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Left: Relative change in mean precipitation rates. Right: change in precipitation rates related to atmospheric rivers

 

In the study a suite of CMIP5 global models were downscaled to a resolution 0f 0.22°. It was found that over most of Europe river-induced precipitation rates increased more than mean precipitation rates (figure below). Only over the Iberian Peninsula and the western coast of Norway river induced precipitation rates were lower in a future warmer climate. The lower rates over Norway were attributed to a change in the route rivers take over Europe. In the future climate the majority of ARs are routed more from southern Europe to the north while the potion arriving directly from the North Atlantic diminished. Accordingly ARs travel longer distances over the continent which reduces their moisture content. In southern Europe river induced precipitation as well as mean precipitation rates lower, but the lowering in mean rates is stronger.

original study:

Gröger, M., Dieterich, C., Dutheil, C., Meier, H. E. M., and Sein, D. V.: Atmospheric rivers in CMIP5 climate ensembles downscaled with a high-resolution regional climate model, Earth Syst. Dynam., 13, 613–631, https://doi.org/10.5194/esd-13-613-2022, 2022

 

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