Atmospheric River
   HOME

TheInfoList



OR:

An atmospheric river (AR) is a narrow corridor or filament of concentrated moisture in the
atmosphere An atmosphere () is a layer of gases that envelop an astronomical object, held in place by the gravity of the object. A planet retains an atmosphere when the gravity is great and the temperature of the atmosphere is low. A stellar atmosph ...
. Other names for this phenomenon are tropical plume, tropical connection, moisture plume, water vapor surge, and cloud band. Atmospheric rivers consist of narrow bands of enhanced
water vapor Water vapor, water vapour, or aqueous vapor is the gaseous phase of Properties of water, water. It is one Phase (matter), state of water within the hydrosphere. Water vapor can be produced from the evaporation or boiling of liquid water or from th ...
transport, typically along the boundaries between large areas of divergent surface air flow, including some frontal zones in association with
extratropical cyclone Extratropical cyclones, sometimes called mid-latitude cyclones or wave cyclones, are low-pressure areas which, along with the anticyclones of high-pressure areas, drive the weather over much of the Earth. Extratropical cyclones are capable of p ...
s that form over the oceans. 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.


Description

The term was originally coined by researchers Reginald Newell and Yong Zhu of the
Massachusetts Institute of Technology The Massachusetts Institute of Technology (MIT) is a Private university, private research university in Cambridge, Massachusetts, United States. Established in 1861, MIT has played a significant role in the development of many areas of moder ...
in the early 1990s to reflect the narrowness of the moisture plumes involved. Atmospheric rivers are typically several thousand kilometers long and only a few hundred kilometers wide, and a single one can carry a greater flux of water than Earth's largest river, the Amazon River. There are typically 3–5 of these narrow plumes present within a hemisphere at any given time. These have been increasing in intensity slightly over the past century. In the current research field of atmospheric rivers, the length and width factors described above in conjunction with an integrated water vapor depth greater than 2.0 cm are used as standards to categorize atmospheric river events. A January 2019 article in
Geophysical Research Letters ''Geophysical Research Letters'' is a biweekly peer-reviewed scientific journal of geoscience published by the American Geophysical Union that was established in 1974. The editor-in-chief iKristopher Karnauskas Aims and scope The journal aims for ...
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." As data modeling techniques progress, integrated water vapor transport (IVT) is becoming a more common data type used to interpret atmospheric rivers. Its strength lies in its ability to show the transportation of water vapor over multiple time steps instead of a stagnant measurement of water vapor depth in a specific air column (integrated water vapor – IWV). In addition, IVT is more directly attributed to orographic precipitation, a key factor in the production of intense rainfall and subsequent flooding.


Scale

Th
Center for Western Weather and Water Extremes
(CW3E) at the
Scripps Institution of Oceanography Scripps Institution of Oceanography (SIO) is the center for oceanography and Earth science at the University of California, San Diego. Its main campus is located in La Jolla, with additional facilities in Point Loma. Founded in 1903 and incorpo ...
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. The scale was developed by F. Martin Ralph, director of CW3E, who collaborated with Jonathan Rutz from the
National Weather Service The National Weather Service (NWS) is an Government agency, agency of the Federal government of the United States, United States federal government that is tasked with providing weather forecasts, warnings of hazardous weather, and other weathe ...
and other experts. The scale considers both the amount of water vapor transported and the duration of the event. Atmospheric rivers receive a preliminary rank according to the 3-hour average maximum vertically integrated water vapor transport. Those lasting less than 24 hours are demoted by one rank, while those lasting longer than 48 hours are increased by one rank. Examples of different atmospheric river categories include the following historical storms: # February 2, 2017; lasted 24 hours # November 19–20, 2016; lasted 42 hours # October 14–15, 2016; lasted 36 hours and produced 5–10 inches of rainfall # January 8–9, 2017; lasted 36 hours and produced 14 inches of rainfall # December 29, 1996 – January 2, 1997; lasted 100 hours and caused >$1 billion in damage Typically, the Oregon coast averages one Cat 4 atmospheric river (AR) each year; Washington state averages one Cat 4 AR every two years; the San Francisco Bay Area averages one Cat 4 AR every three years; and southern California, which typically experiences one Cat 2 or Cat 3 AR each year, averages one Cat 4 AR every ten years. ''Usage:'' In practice, the AR scale can be used to refer to "conditions" without reference to the word "category", as in this excerpt from the CW3E Scripps Twitter feed: "Late-season atmospheric river to bring precipitation to the high elevations over northern California, western Oregon, and Washington this weekend, with AR 3 conditions forecast over southern Oregon."


Impacts

Atmospheric rivers have a central role in the global
water cycle The water cycle (or hydrologic cycle or hydrological cycle) is a biogeochemical cycle that involves the continuous movement of water on, above and below the surface of the Earth across different reservoirs. The mass of water on Earth remains fai ...
. On any given day, atmospheric rivers account for over 90% of the global meridional (north-south) water vapor transport, yet they cover less than 10% of any given extratropical line of latitude. Atmospheric rivers are also known to contribute to about 22% of total global runoff. They are also the major cause of extreme
precipitation In meteorology, precipitation is any product of the condensation of atmospheric water vapor that falls from clouds due to gravitational pull. The main forms of precipitation include drizzle, rain, rain and snow mixed ("sleet" in Commonwe ...
events that cause severe
flood A flood is an overflow of water (list of non-water floods, or rarely other fluids) that submerges land that is usually dry. In the sense of "flowing water", the word may also be applied to the inflow of the tide. Floods are of significant con ...
ing in many mid-latitude, westerly coastal regions of the world, including the west coast of North America, Western Europe, the west coast of
North Africa North Africa (sometimes Northern Africa) is a region encompassing the northern portion of the African continent. There is no singularly accepted scope for the region. However, it is sometimes defined as stretching from the Atlantic shores of t ...
, the Iberian Peninsula, Iran and New Zealand. Equally, the absence of atmospheric rivers has been linked with the occurrence of droughts in several parts of the world, including South Africa, Spain and Portugal.


United States

The inconsistency of California's rainfall is due to the variability in strength and quantity of these storms, which can produce strenuous effects on California's water budget. The factors described above make California a perfect case study to show the importance of proper water management and prediction of these storms. The significance that atmospheric rivers have for the control of coastal water budgets juxtaposed against their creation of detrimental floods can be constructed and studied by looking at California and the surrounding coastal region of the western United States. In this region atmospheric rivers have contributed 30–50% of total annual rainfall according to a 2013 study. The Fourth
National Climate Assessment The National Climate Assessment (NCA) is an initiative within the U.S. federal government focused on climate change science, formed under the auspices of the Global Change Research Act of 1990. Background The NCA is a major product of the U. ...
(NCA) report, released by the
U.S. Global Change Research Program The United States Global Change Research Program (USGCRP) coordinates and integrates federal research on changes in the global environment and their implications for society. The program began as a presidential initiative in 1989 and was codified b ...
(USGCRP) on November 23, 2018 confirmed that along the U.S. western coast, landfalling atmospheric rivers "account for 30%–40% of precipitation and snowpack. These landfalling atmospheric rivers "are associated with severe flooding events in California and other western states." The USGCRP team of thirteen federal agencies—the DOA,
DOC DOC, Doc, doc or DoC may refer to: People and characters * Doc, an abbreviation of doctor * Doc (nickname) * Doc (mascot), the Towson University mascot Persons * The D.O.C., American rapper (born 1968) * Doc Gallows (born 1983), ring nam ...
, DOD, DOE, HHS, DOI,
DOS DOS (, ) is a family of disk-based operating systems for IBM PC compatible computers. The DOS family primarily consists of IBM PC DOS and a rebranded version, Microsoft's MS-DOS, both of which were introduced in 1981. Later compatible syste ...
, DOT, EPA,
NASA The National Aeronautics and Space Administration (NASA ) is an independent agencies of the United States government, independent agency of the federal government of the United States, US federal government responsible for the United States ...
, NSF,
Smithsonian Institution The Smithsonian Institution ( ), or simply the Smithsonian, is a group of museums, Education center, education and Research institute, research centers, created by the Federal government of the United States, U.S. government "for the increase a ...
, and the
USAID The United States Agency for International Development (USAID) is an agency of the United States government that has been responsible for administering civilian United States foreign aid, foreign aid and development assistance. Established in 19 ...
—with the assistance of "1,000 people, including 300 leading scientists, roughly half from outside the government" reported that, "As the world warms, the "landfalling atmospheric rivers on the West Coast are likely to increase" in "frequency and severity" because of "increasing evaporation and higher atmospheric water vapor levels in the atmosphere." Based on the North American Regional Reanalysis (NARR) analyses, a team led by
National Oceanic and Atmospheric Administration The National Oceanic and Atmospheric Administration (NOAA ) is an American scientific and regulatory agency charged with Weather forecasting, forecasting weather, monitoring oceanic and atmospheric conditions, Hydrography, charting the seas, ...
'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. According to a May 14, 2019 article in
San Jose, California San Jose, officially the City of San José ( ; ), is a cultural, commercial, and political center within Silicon Valley and the San Francisco Bay Area. With a city population of 997,368 and a metropolitan area population of 1.95 million, it is ...
's ''
The Mercury News ''The Mercury News'' (formerly ''San Jose Mercury News'', often locally known as ''The Merc'') is a morning daily newspaper published in San Jose, California, in the San Francisco Bay Area. It is published by the Bay Area News Group, a subsidia ...
'', atmospheric rivers, "giant conveyor belts of water in the sky", cause the moisture-rich " Pineapple Express" storm systems that come from the Pacific Ocean several times annually and account for about 50 percent of California's annual precipitation and are often associated with baroclinic rossby waves. University of California at San Diego's Center for Western Weather and Water Extremes's director Marty Ralph, who is one of the United States' experts on atmospheric river storms and has been active in AR research for many years, said that, atmospheric rivers are more common in winter. For example, from October 2018 to spring 2019, there were 47 atmospheric rivers, 12 of which were rated strong or extreme, in Washington, Oregon and California. The rare May 2019 atmospheric rivers, classified as Category 1 and Category 2, are beneficial in terms of preventing seasonal wildfires but the "swings between heavy rain and raging wildfires" are raising questions about moving from "understanding that the climate is changing to understanding what to do about it." Atmospheric rivers have caused an average of $1.1 billion in damage annually, much of it occurring in
Sonoma County Sonoma County ( ) is a county located in the U.S. state of California. As of the 2020 United States census, its population was 488,863. Its seat of government and largest city is Santa Rosa. Sonoma County comprises the Santa Rosa-Petaluma ...
, California, according to a December 2019 study by the Scripps Institution on Oceanography at
UC San Diego The University of California, San Diego (UC San Diego in communications material, formerly and colloquially UCSD) is a public land-grant research university in San Diego, California, United States. Established in 1960 near the pre-existing Sc ...
and the US Army Corps of Engineers, which analyzed data from the
National Flood Insurance Program The National Flood Insurance Program (NFIP) is a program created by the Congress of the United States in 1968 through the National Flood Insurance Act of 1968 (P.L. 90-448). The NFIP has two purposes: to share the risk of flood losses through fl ...
and the
National Weather Service The National Weather Service (NWS) is an Government agency, agency of the Federal government of the United States, United States federal government that is tasked with providing weather forecasts, warnings of hazardous weather, and other weathe ...
. Just twenty counties suffered almost 70% of the damage, the study found, and that one of the main factors in the scale of damage appeared to be the number of properties located in a
flood plain A floodplain or flood plain or bottomlands is an area of land adjacent to a river. Floodplains stretch from the banks of a river channel to the base of the enclosing valley, and experience flooding during periods of high Discharge (hydrolog ...
. These counties were:


Canada

According to a January 22, 2019 article in ''
Geophysical Research Letters ''Geophysical Research Letters'' is a biweekly peer-reviewed scientific journal of geoscience published by the American Geophysical Union that was established in 1974. The editor-in-chief iKristopher Karnauskas Aims and scope The journal aims for ...
'', the Fraser River Basin (FRB), a "snow-dominated watershed"According to the Curry et al article, "Snow-dominated watersheds are bellwethers of climate change." in British Columbia, is exposed to landfalling ARs, originating over the tropical Pacific Ocean that bring "sustained, heavy precipitation" throughout the winter months. The authors predict that based on their modelling "extreme rainfall events resulting from atmospheric rivers may lead to peak annual floods of historic proportions, and of unprecedented frequency, by the late 21st century in the Fraser River Basin." In November 2021, massive flooding in the Fraser River Basin near Vancouver was attributed to a series of atmospheric rivers.


Iran

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. However, a rare atmospheric river was found responsible for the record floods of March 2019 in Iran that damaged one-third of the country's infrastructures and killed 76 people. That AR was named Dena, after the peak of the Zagros Mountains, which played a crucial role in precipitation formation. AR Dena started its long, 9000 km journey from the Atlantic Ocean and travelled across North Africa before its final landfall over the Zagros Mountains. 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. Water transport by AR Dena was equivalent to more than 150 times the aggregated flow of the four major rivers in the region (
Tigris The Tigris ( ; see #Etymology, below) is the eastern of the two great rivers that define Mesopotamia, the other being the Euphrates. The river flows south from the mountains of the Armenian Highlands through the Syrian Desert, Syrian and Arabia ...
,
Euphrates The Euphrates ( ; see #Etymology, below) is the longest and one of the most historically important rivers of West Asia. Tigris–Euphrates river system, Together with the Tigris, it is one of the two defining rivers of Mesopotamia (). Originati ...
, Karun and Karkheh). The intense rains made the 2018-2019 rainy season the wettest in the past half century, a sharp contrast with the prior year, which was the driest over the same period. Thus, this event is a compelling example of rapid dry-to-wet transitions and intensification of extremes, potentially resulting from the climate change.


Australia

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. They are more frequent when temperatures in the eastern Indian Ocean near Australia are warmer than those in the western Indian Ocean (i.e. a negative Indian Ocean Dipole). Atmospheric rivers also form in the waters to the east and south of Australia and are most common during the warmer months.


Europe

According to an article in ''
Geophysical Research Letters ''Geophysical Research Letters'' is a biweekly peer-reviewed scientific journal of geoscience published by the American Geophysical Union that was established in 1974. The editor-in-chief iKristopher Karnauskas Aims and scope The journal aims for ...
'' 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.


Satellites and sensors

According to a 2011 ''
Eos In ancient Greek mythology and Ancient Greek religion, religion, Eos (; Ionic Greek, Ionic and Homeric Greek ''Ēṓs'', Attic Greek, Attic ''Héōs'', "dawn", or ; Aeolic Greek, Aeolic ''Aúōs'', Doric Greek, Doric ''Āṓs'') is the go ...
'' magazine article''
Eos In ancient Greek mythology and Ancient Greek religion, religion, Eos (; Ionic Greek, Ionic and Homeric Greek ''Ēṓs'', Attic Greek, Attic ''Héōs'', "dawn", or ; Aeolic Greek, Aeolic ''Aúōs'', Doric Greek, Doric ''Āṓs'') is the go ...
, Transactions'' is published weekly by the
American Geophysical Union The American Geophysical Union (AGU) is a 501(c)(3) nonprofit organization of Earth, Atmospheric science, atmospheric, Oceanography, ocean, Hydrology, hydrologic, Astronomy, space, and Planetary science, planetary scientists and enthusiasts that ...
and covers topics related to
earth science Earth science or geoscience includes all fields of natural science related to the planet Earth. This is a branch of science dealing with the physical, chemical, and biological complex constitutions and synergistic linkages of Earth's four spheres ...
.
by 1998, the spatiotemporal coverage of water vapor data over oceans had vastly improved through the use of "microwave
remote sensing Remote sensing is the acquisition of information about an physical object, object or phenomenon without making physical contact with the object, in contrast to in situ or on-site observation. The term is applied especially to acquiring inform ...
from polar-orbiting satellites", such as the
special sensor microwave/imager The Special Sensor Microwave/Imager (SSM/I) is a seven-channel, four-frequency, linearly polarized passive microwave radiometer system.Hollinger, J.P. 1989: ''DMSP Special Sensor Microwave/Imager Calibration/Validation''. Final Report, Vol. I., Spac ...
(SSM/I). This led to greatly increased attention to the "prevalence and role" of atmospheric rivers. Prior to the use of these satellites and sensors, scientists were mainly dependent on weather balloons and other related technologies that did not adequately cover oceans. SSM/I and similar technologies provide "frequent global measurements of integrated water vapor over the Earth's oceans."


See also

*
Tropical upper tropospheric trough A tropical upper tropospheric trough (TUTT), also known as the mid-oceanic trough, is a trough situated in the upper-level (at about 200 hPa) tropics. Its formation is usually caused by the intrusion of energy and wind from the mid-latitudes into ...
, a band of moisture common in tropical regions * ARkStorm, a hypothetical storm by the same name that could affect California * Great Flood of 1862 (massive flooding in US West) * Atmospheric lake
ARTMIP
Atmospheric River Tracking Method Intercomparison Project, quantifies uncertainties due to how an atmospheric river is defined, especially for climate studies


Notes


References


Further reading

*
Climate change may lead to bigger atmospheric rivers
-
NASA The National Aeronautics and Space Administration (NASA ) is an independent agencies of the United States government, independent agency of the federal government of the United States, US federal government responsible for the United States ...


External links


Current map of predicted global precipitation for the next three hoursCBS News segment; Jan. 31, 2024
CBS News environmental reporter Ben Tracy joined a team of scientists from
NOAA The National Oceanic and Atmospheric Administration (NOAA ) is an American scientific and regulatory agency charged with forecasting weather, monitoring oceanic and atmospheric conditions, charting the seas, conducting deep-sea exploratio ...
as they dropped electronic monitoring instruments into an atmospheric river during a high-altitude reconnaissance flight over the Pacific Ocean.
{{Authority control Atmospheric dynamics Atmospheric circulation Clouds, fog and precipitation Meteorological phenomena Severe weather and convection