Tornado Alley (PROG)

[F6]

California rains put spotlight on atmospheric rivers

On 7 February, water vapor streamed from Hawaii on an atmospheric river called the Pineapple Express.
Feb. 22, 2017
http://www.sciencemag.org/news/2017/02/california-rains-put-spotlight-atmospheric-rivers [no comments yet]


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New Research Shows How 'Atmospheric Rivers' Wreak Havoc Around The Globe

Atmospheric rivers are sinews of moisture from the tropics. The one pictured here appeared over the Northern Pacific on Jan. 3.


A storm on Jan. 10 dumped several inches [sic - feet] of snow over the Pacific Northwest. Atmospheric rivers like these funnel moisture from the tropics.
February 20, 2017
http://www.npr.org/sections/thetwo-way/2017/02/20/515838078/new-research-shows-how-atmospheric-rivers-wreak-havoc-around-the-globe


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Extreme winds and precipitation during landfall of atmospheric rivers
Nature Geoscience (2017) doi:10.1038/ngeo2894
Published online 20 February 2017
Abstract
Atmospheric rivers—long, narrow filaments of large integrated water vapour transport—are associated with weather and water extremes, such as precipitation extremes and flooding in western North America and northern Europe. Here we apply a global detection algorithm for atmospheric rivers to reanalysis data during 1997–2014 to investigate the impact of atmospheric rivers on wind extremes as well as precipitation extremes. We find that atmospheric rivers are associated with up to half of the extreme events in the top 2% of the precipitation and wind distribution, across most mid-latitude regions globally. Landfalling atmospheric rivers are associated with about 40–75% of extreme wind and precipitation events over 40% of the world’s coastlines. Atmospheric rivers are associated with a doubling or more of the typical wind speed compared to all storm conditions, and a 50–100% increase in the wind and precipitation values for extreme events. We also find that the majority of extreme wind events catalogued between 1997 and 2013 over Europe with billion US dollar losses were associated with atmospheric rivers. We conclude that landfalling atmospheric rivers can represent a significant hazard around the globe, because of their association with not only extreme precipitation, but also extreme winds.
http://www.nature.com/ngeo/journal/vaop/ncurrent/full/ngeo2894.html , full access http://www.nature.com/articles/ngeo2894.epdf?referrer_access_token=Z36ZiLhJQBkcWS-yqZlj29RgN0jAjWel9jnR3ZoTv0OWprtsX0x9GBWfyri-xdJ7qED_eY-ZHTDFER80s-0Mu_TexciHAFEEuoFSeg7FU9cg4dCX5utZhCmH_Ln0SMRwzEWXLNkdqaRk-NCfU3hQAKs5iAtUoBpvK40-2qyafG41TltwZ6Nb7q4v5GEa9viyt-FOiUTF3kao0iOnC3MRwgTfqUoUxqj4HM6FulTpgsg_IzRnlUpHsYjgMeYpngp9


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Every 200 years California suffers a storm of biblical proportions — this year’s rains are just a precursor


Yes, that's a waterfall behind the house. Anderson dam spillway in full force now.
1:31 PM - 20 Feb 2017
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Yes, that's a waterfall behind the house. Anderson dam spillway in full force now. #CaliforniaStorms @CBSSF pic.twitter.com/B54AWVHbsM

— Len Ramirez (@lenKPIX) February 20, 2017

(with comments)]

The last freak rainstorm turned the Central Valley into a lake, and we’re due for another one
Feb 21, 2017
[...]
In a typical year, around nine [ http://www.atmosedu.com/Geol390/articles/ComingMegaFloos4.pdf ] atmospheric rivers shower California with precipitation. They’re a critical source of about a third to half [ https://www.esrl.noaa.gov/psd/atmrivers/ ] of the annual water in a state where the summers are usually bone-dry. But they also frequently go hand in hand with devastating wind storms, which can cause billions of dollars of damage, according to a study published Monday in the journal Nature Geosciences [full access http://www.nature.com/articles/ngeo2894.epdf?referrer_access_token=Z36ZiLhJQBkcWS-yqZlj29RgN0jAjWel9jnR3ZoTv0OWprtsX0x9GBWfyri-xdJ7qED_eY-ZHTDFER80s-0Mu_TexciHAFEEuoFSeg7FU9cg4dCX5utZhCmH_Ln0SMRwzEWXLNkdqaRk-NCfU3hQAKs5iAtUoBpvK40-2qyafG41TltwZ6Nb7q4v5GEa9viyt-FOiUTF3kao0iOnC3MRwgTfqUoUxqj4HM6FulTpgsg_IzRnlUpHsYjgMeYpngp9 (just above)].
“When we get a sequence of them, or we get too many and the soils are real moist and the rivers are high and the reservoirs are full, then they can go from being largely beneficial — because we need water in the West — to hazards,” Ralph says.
That’s the situation we’re in now, Ralph says, with about 30 atmospheric rivers since October 1st — and it’s something we can expect to see more of. As global temperatures continue to climb, the air can hold more water vapor — which means calmer winds, but warmer and wetter atmospheric rivers [ https://ca.water.usgs.gov/pubs/2011/climate-change-atmospheric-rivers-floods-california-dettinger.pdf ], more often. And that means more flooding.
“This situation that we’re seeing with the pronounced drought punctuated by wet conditions that are producing a lot of runoff — that is exactly what we are seeing intensify in the historical record,” says Noah Diffenbaugh [ https://woods.stanford.edu/about/woods-faculty/noah-diffenbaugh ], a professor of Earth Sciences at Stanford University. “And it’s exactly what climate models project for the future.”
Climate change could exacerbate the dynamic as we struggle with an aging and already failing infrastructure. We can probably expect more, and worse catastrophes than Oroville’s crumbling spillway. That’s why Newsha Ajami [ http://waterinthewest.stanford.edu/about/people/newsha-ajami ], Stanford’s director of Urban Water Policy, says, “Coming up with new more innovative management and operational rules that reflect the 21st century climatic realities — I think that is really an important issue.”
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http://www.theverge.com/2017/2/21/14684630/california-atmospheric-river-flood-storm-evacuations-rain-arkstorm [with embedded videos, and comments]


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