Atmospheric River Storms Are Now Characterized With The Help Of A New Scale

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A new scale was created in order to describe the impacts and the strength of the “atmospheric rivers”. The new scale was made by researchers from the Scripps Institution of Oceanography at the University of California San Diego.

“The scale recognizes that weak ARs are often most beneficial because they can enhance water supply and snow pack, while stronger ARs can become mostly hazardous, for example if they strike an area with conditions that enhance vulnerability, such as burn scars, or already wet conditions. Extended durations can enhance impacts.,” explained the co-authors in the paper which was published in the Bulletin of the American Meteorological Society.

The ranks

There are five different scale ranks ARs: AR Cat 1, which is weak; AR Cat 2, moderate; AR Cat 3, Strong; AR Cat 4, Extreme and AR Cat 5, Exceptional. The first rank is mostly beneficial, while the last one is primarily hazardous. The other ranks are misked.

“The concept of ARs has directly benefited NWS operations in the West through better scientific understanding, more accurate precipitation forecasts, and a better vehicle for communicating impacts to our partners,” added Rutz. “The AR scale is a significant step forward, providing forecasters with a tool to distinguish between primarily beneficial and primarily hazardous storms. I anticipate that this scale will be adopted and highly used.”

Researchers hope that this new scale will bring awareness. This way, people will know to make the differences between AR types.

“This scale enables improved awareness of the potential benefit versus hazard of a forecast AR,” said co-author Michael Anderson. “It can serve as a focal point for discussion between water managers, emergency response personnel and the research community as these key water supply and flood inducing storms continue to evolve in a changing climate.”