Washington: A new study led by NASA of "atmospheric river" storms from the Pacific Ocean may help researchers 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 vapour from tropical oceans to mid-latitude land areas-are prolific producers of rain and snow on California`s Sierra Nevada mountains.
Bin Guan of the Joint Institute for Regional Earth System Science and Engineering, a collaboration between NASA`s Jet Propulsion Laboratory (JPL) in Pasadena, California, and the University of California Los Angeles (UCLA), led a team of scientists from NASA, UCLA , and the National Oceanic and Atmospheric Administration (NOAA) to study how two of the most common atmospheric circulation patterns in the Northern Hemisphere interact with atmospheric rivers.
Guan said that atmospheric rivers are the bridge between climate and West Coast snow and if scientists can predict these atmospheric patterns with reasonable lead times, they`ll have a better understanding of water availability and flooding in the region.
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 (AO) and the Pacific/North American teleconnection (PNA). 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 Nino and La Nina patterns do in the tropical Pacific.
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.
The findings have been published in the journal Water Resources Research.