Atmospheric river
[1][2] Atmospheric rivers consist of narrow bands of enhanced water vapor transport, typically along the boundaries between large areas of divergent surface air flow, including some frontal zones in association with extratropical cyclones that form over the oceans.
[3][4][5][6] Pineapple Express storms are the most commonly represented and recognized type of atmospheric rivers; the name is due to the warm water vapor plumes originating over the Hawaiian tropics that follow various paths towards western North America, arriving at latitudes from California and the Pacific Northwest to British Columbia and even southeast Alaska.
[7][8][9] [10] The term was originally coined by researchers Reginald Newell and Yong Zhu of the Massachusetts Institute of Technology in the early 1990s to reflect the narrowness of the moisture plumes involved.
[8][13][14][15] A January 2019 article in Geophysical Research Letters described them as "long, meandering plumes of water vapor often originating over the tropical oceans that bring sustained, heavy precipitation to the west coasts of North America and northern Europe.
[15] The Center for Western Weather and Water Extremes (CW3E) at the Scripps Institution of Oceanography released a five-level scale in February 2019 to categorize atmospheric rivers, ranging from "weak" to "exceptional" in strength, or "beneficial" to "hazardous" in impact.
"[7][30][32][33][34] Based on the North American Regional Reanalysis (NARR) analyses, a team led by National Oceanic and Atmospheric Administration's (NOAA) Paul J. Neiman, concluded in 2011 that landfalling ARs were "responsible for nearly all the annual peak daily flow (APDF)s in western Washington" from 1998 through 2009.
These counties were:[37] According to a January 22, 2019 article in Geophysical Research Letters, the Fraser River Basin (FRB), a "snow-dominated watershed"[Note 1] in British Columbia, is exposed to landfalling ARs, originating over the tropical Pacific Ocean that bring "sustained, heavy precipitation" throughout the winter months.
[40] While a large body of research has shown the impacts of the atmospheric rivers on weather-related natural disasters over the western U.S. and Europe, little is known about their mechanisms and contribution to flooding in the Middle East.
Specific synoptic weather conditions, including tropical-extratropical interactions of the atmospheric jets, and anomalously warm sea-surface temperatures in all surrounding basins provided the necessary ingredients for formation of this AR.
In Australia, northwest cloud bands are sometimes associated with atmospheric rivers that originate in the Indian Ocean and cause heavy rainfall in northwestern, central, and southeastern parts of the country.
[43] According to an article in Geophysical Research Letters by Lavers and Villarini, 8 of the 10 highest daily precipitation records in the period 1979–2011 have been associated with atmospheric rivers events in areas of Britain, France and Norway.
[44] According to a 2011 Eos magazine article[Note 2] by 1998, the spatiotemporal coverage of water vapor data over oceans had vastly improved through the use of "microwave remote sensing from polar-orbiting satellites", such as the special sensor microwave/imager (SSM/I).
