Uncategorized

November 13, 2013

Study finds climate link to ‘atmospheric river’ storms

A new NASA-led study of “atmospheric river” storms from the Pacific Ocean may help scientists better predict major winter snowfalls that hit West Coast mountains and lead to heavy spring runoff and sometimes flooding.

Atmospheric rivers — short-lived wind tunnels that carry water vapor from tropical oceans to mid-latitude land areas – are prolific producers of rain and snow on California’s Sierra Nevada mountains.

The finding, published in the journal Water Resources Research, has major implications for water management in the West, where Sierra runoff is used for drinking water, agriculture and hydropower.

The research team studied how two of the most common atmospheric circulation patterns in the Northern Hemisphere interact with atmospheric rivers. They found when those patterns line up in a certain way, they create a virtual freeway that leads the moisture-laden winds straight to the Sierras.

Bin Guan of the Joint Institute for Regional Earth System Science and Engineering, a collaboration between NASA’s Jet Propulsion Laboratory in Pasadena, Calif., and the University of California Los Angeles, led a team of scientists from NASA, UCLA , and the National Oceanic and Atmospheric Administration on this research.

An atmospheric river is a narrow stream of wind, about a mile high and sometimes of hurricane strength. Crossing the warm tropical Pacific in a few days, it becomes laden with water vapor. A moderate-sized atmospheric river carries as much water as the Mississippi River dumps into the Gulf of Mexico in an average week. When the river comes ashore and stalls over higher terrain, the water falls as snow or rain.

“Atmospheric rivers are the bridge between climate and West Coast snow,” said Guan. “If scientists can predict these atmospheric patterns with reasonable lead times, we’ll have a better understanding of water availability and flooding in the region.” The benefit of improving flood prediction alone would be significant. A single California atmospheric-river storm in 1999 caused 15 deaths and $570 million in damage.

Guan’s team used data from the JPL-developed Atmospheric Infrared Sounder (AIRS) instrument on NASA’s Aqua satellite, along with NOAA satellite data and snowpack data from the California Department of Water Resources. They looked at the extremely snowy winter of 2010-2011, when 20 atmospheric rivers made landfall.

The team compared the dates of these events with the phases of the Arctic Oscillation and the Pacific/North American teleconnection. These large-scale weather patterns wax and wane, stretching thousands of miles across the atmosphere and shaping the climate of the mid-latitudes, somewhat as the better-known El NiÒo and La NiÒa patterns do in the tropical Pacific.

Each pattern affects a different part of the Northern Hemisphere by seesawing between phases of lower-than-average and higher-than-average air pressure over various parts of the globe. For example, the negative phase of the AO is associated with higher pressure in the Arctic and lower pressure in the surrounding lower latitudes. In the positive phase, those highs and lows are reversed.

The phases of each pattern change irregularly and at varying intervals. The researchers charted these phases throughout the winter of 2010-2011. During 15 of the winter’s 20 atmospheric river occurrences, both patterns were in the negative phase. The team then looked at the period 1998-2011 and found a similar correspondence: more atmospheric rivers occurred when both patterns were negative.

According to Guan, in the double-negative periods the high- and low-pressure systems associated with that phase in each pattern mesh to create a lingering atmospheric low-pressure system just northwest of California. That low directs the atmospheric river fire hose straight toward the Sierra Nevadas.
Guan points out that the double-negative phase correlation is rare.

“I looked at 50 years of atmospheric data. Only five months had those phases of the PNA and AO occurring together for more than 15 days of the month,” he said.

AIRS was built and is managed by JPL for NASA’s Science Mission Directorate in Washington. Aqua is managed by NASA’s Goddard Space Flight Center, Greenbelt, Md. JPL is a division of the California Institute of Technology in Pasadena.




All of this week's top headlines to your email every Friday.


 
 

 

Headlines April 23, 2014

News: U.S. conducts spy flights over Russia - After a tit-for-tat series of delays, the United States conducted an Open Skies Treaty intelligence flight over Russian territory April 21, a State Department official said.  Army paratroopers heading to Poland after Russian annexation of Crimea - U.S. Army paratroopers are arriving in Poland to begin a series of...
 
 

News Briefs April 23, 2014

U.S. military deaths in Afghanistan at 2,177 As of April 22, 2014, at least 2,177 members of the U.S. military had died in Afghanistan as a result of the U.S.-led invasion of Afghanistan in late 2001, according to an Associated Press count. The AP count is one less than the Defense Department’s tally. At least...
 
 

Northrop Grumman sets new greenhouse gas emission reduction goal of 30 percent by 2020

Northrop Grumman announced April 22 its commitment to reduce greenhouse gas emissions by 30 percent from 2010 levels by 2020, as part of its commemoration of Earth Day.   “Northrop Grumman is dedicated to top performance in environmental sustainability,” said Wes Bush, chairman, chief executive officer and president. “This new goal sets the bar significantly...
 

 

Lockheed Martin demonstrates enhanced ground control system, software for small UAV

Lockheed Martin’s Group 1 family of unmanned aircraft systems is migrating to enhanced automation capabilities using its Kestrelô “Fly Light” flight control systems and industry-leading mobile Ground Control Station software. The increased automation allows operators to focus on executing the mission, rather than flying various aircraft. Earlier this year, Lockheed MartinR...
 
 

U.S. Navy awards General Dynamics $33 million to operate, maintain military sealift ships

The U.S. Navy has awarded General Dynamics American Overseas Marine LLC a $32.7 million contract modification to operate and maintain seven large, medium-speed, roll-on / roll-off ships for the Military Sealift Command. AMSEA is a wholly owned subsidiary of General Dynamics. Under the terms of the modification, AMSEA will provide services including crewing, engineering, maintenance,...
 
 

US Navy deploys Standard Missile-3 Block IB for first time

In partnership with the Missile Defense Agency, the U.S. Navy deployed the second-generation Standard Missile-3 Block IB made by Raytheon for the first time, initiating the second phase of the Phased Adaptive Approach. “The SM-3 Block IB’s completion of initial operational testing last year set the stage for a rapid deployment to theater,” said Dr....
 




0 Comments


Be the first to comment!


Leave a Reply

Your email address will not be published. Required fields are marked *

You may use these HTML tags and attributes: <a href="" title=""> <abbr title=""> <acronym title=""> <b> <blockquote cite=""> <cite> <code> <del datetime=""> <em> <i> <q cite=""> <strike> <strong>