View source for Atmospheric river

{{Short description|Narrow corridor of concentrated moisture in the atmosphere}}
[[File:The science behind atmospheric rivers.jpg|thumb|An explanation from the [[National Weather Service]] on atmospheric rivers]]
An '''atmospheric river''' ('''AR''') is a narrow corridor or filament of concentrated moisture in the [[atmosphere]]. Other names for this phenomenon are '''tropical plume''', '''tropical connection''', '''moisture plume''', '''water vapor surge''', and '''cloud band'''.<ref>{{cite web
 | url =https://www.esrl.noaa.gov/psd/arportal/about/
 | title =Atmospheric River Information Page
 | website =NOAA Earth System Research Laboratory}}</ref><ref>{{cite web|url=https://www.abc.net.au/news/2020-08-11/twin-atmospheric-rivers-form-in-sky-over-australia/12543430|title=Atmospheric rivers form in both the Indian and Pacific Oceans, bringing rain from the tropics to the south|work=ABC news|date=11 August 2020|access-date=11 August 2020}}</ref>

[[File:NASA_Atmospheric_river_AsiaNA2017_10_26.jpg|thumb|Composite satellite photos of an atmospheric river connecting Asia to North America in October 2017|alt=Two wide photos showing a long stream of clouds ranging over the Pacific Ocean]]{{Weather}}
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 [[Weather front|frontal zone]]s in association with [[extratropical cyclone]]s that form over the oceans.<ref name="ar94">{{cite journal|last=Zhu |first=Yong |author2=Reginald E. Newell |title=Atmospheric rivers and bombs |journal=[[Geophysical Research Letters]] |year=1994 |volume=21 |issue=18 |pages=1999–2002 |doi= 10.1029/94GL01710 |url=http://paos.colorado.edu/~dcn/ATOC6020/papers/AtmosphericRivers_94GL01710.pdf |bibcode=1994GeoRL..21.1999Z |url-status=dead |archive-url=https://web.archive.org/web/20100610063041/http://paos.colorado.edu/~dcn/ATOC6020/papers/AtmosphericRivers_94GL01710.pdf |archive-date=2010-06-10 }}</ref><ref name="mwr98">{{cite journal|last=Zhu|first=Yong|author2=Reginald E. Newell|title=A Proposed Algorithm for Moisture Fluxes from Atmospheric Rivers|journal=Monthly Weather Review |year= 1998|volume=126|issue=3|pages= 725–735|doi=10.1175/1520-0493(1998)126<0725:APAFMF>2.0.CO;2 |issn= 1520-0493|bibcode = 1998MWRv..126..725Z |doi-access=free}}</ref><ref name="sci06">{{cite journal|last=Kerr |first= Richard A.|title=Rivers in the Sky Are Flooding The World With Tropical Waters|journal=Science |date= 28 July 2006|volume=313|issue=5786|pages=435|doi=10.1126/science.313.5786.435|url=http://tenaya.ucsd.edu/~dettinge/atmos_rivers.science.pdf |pmid=16873624|s2cid=13209226|access-date=14 December 2010|archive-url=https://web.archive.org/web/20100629114901/http://tenaya.ucsd.edu/~dettinge/atmos_rivers.science.pdf|archive-date=29 June 2010|url-status=dead}}</ref><ref name="ncaro">{{cite conference | first = Allen B. | last = White | date = 2009-10-08 | title = The NOAA coastal atmospheric river observatory | url = http://ams.confex.com/ams/34Radar/techprogram/paper_155601.htm | conference = 34th Conference on Radar Meteorology | conference-url = http://ams.confex.com/ams/34Radar/techprogram/program_567.htm|display-authors=etal}}</ref> [[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.<ref name=":0">{{Cite journal|last=Dettinger|first=Michael|date= 2011-06-01|title=Climate Change, Atmospheric Rivers, and Floods in California – A Multimodel Analysis of Storm Frequency and Magnitude Changes1|journal=JAWRA Journal of the American Water Resources Association|language=en|volume=47|issue=3|pages=514–523|doi=10.1111/j.1752-1688.2011.00546.x|issn=1752-1688|bibcode=2011JAWRA..47..514D|s2cid=4691998 }}</ref><ref name=":1">{{Cite journal|last1=Dettinger|first1=Michael D.|last2=Ralph|first2=Fred Martin|last3=Das|first3=Tapash|last4=Neiman|first4=Paul J.|last5= Cayan |first5=Daniel R.|date=2011-03-24|title=Atmospheric Rivers, Floods and the Water Resources of California |journal=Water|language=en|volume=3|issue=2|pages=445–478|doi=10.3390/w3020445|doi-access=free|bibcode=2011Water...3..445D |hdl=10535/7155|hdl-access=free}}</ref><ref>{{Cite journal |last1=Tan |first1=Yaheng |last2=Yang |first2=Song |last3=Zwiers |first3=Francis |last4=Wang |first4=Ziqian |last5=Sun |first5=Qiaohong |date=2022-02-01 |title=Moisture budget analysis of extreme precipitation associated with different types of atmospheric rivers over western North America |url=https://doi.org/10.1007/s00382-021-05933-3 |journal=Climate Dynamics |language=en |volume=58 |issue=3 |pages=793–809 |doi=10.1007/s00382-021-05933-3 |bibcode=2022ClDy...58..793T |s2cid=237218999 |issn=1432-0894}}</ref>

<ref>{{Cite journal |last1=Corringham |first1=Thomas W. |last2=McCarthy |first2=James |last3=Shulgina |first3=Tamara |last4=Gershunov |first4=Alexander |last5=Cayan |first5=Daniel R. |last6=Ralph |first6=F. Martin |date=2022-08-12 |title=Climate change contributions to future atmospheric river flood damages in the western United States |journal=Scientific Reports |language=en |volume=12 |issue=1 |pages=13747 |doi=10.1038/s41598-022-15474-2 |pmid=35961991 |pmc=9374734 |bibcode=2022NatSR..1213747C |issn=2045-2322|doi-access=free }}</ref>

==Description==
[[File:DesmondAtmosphericRiver.png|thumb|Layered precipitable water imagery of particularly strong atmospheric rivers on 5 December 2015. The first, caused by [[Storm Desmond]], stretched from the [[Caribbean]] to the [[United Kingdom]]; the second originated from the [[Philippines]] and crossing the [[Pacific Ocean]] extended to the west coast of North America.]]
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.<ref name="ar94" /><ref name="sci06" /><ref>{{cite journal|last=Newell|first=Reginald E.|author2=Nicholas E. Newell |author3=Yong Zhu |author4=Courtney Scott |title=Tropospheric rivers? – A pilot study|journal=Geophys. Res. Lett.|year=1992|volume=19|issue=24|pages=2401–2404|doi=10.1029/92GL02916|url=https://agupubs.onlinelibrary.wiley.com/doi/10.1029/92GL02916|bibcode=1992GeoRL..19.2401N}}</ref> 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]].<ref name="mwr98" /> There are typically 3–5 of these narrow plumes present within a hemisphere at any given time.   These have been increasing<ref>{{Cite web |date=2022-05-24 |title=Atmospheric rivers, part 2 |url=https://www.abc.net.au/radionational/programs/greatmomentsinscience/atmospheric-rivers-part-2/13896724 |access-date=2022-06-22 |website=ABC Radio National |language=en-AU}}</ref> 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&nbsp;cm are used as standards to categorize atmospheric river events.<ref name=":1" /><ref name="grl06" /><ref>{{Cite journal|last1=Guan|first1=Bin|last2=Waliser|first2=Duane E.|last3=Molotch|first3=Noah P.|last4=Fetzer|first4=Eric J.|last5=Neiman|first5=Paul J.|date=2011-08-24|title=Does the Madden–Julian Oscillation Influence Wintertime Atmospheric Rivers and Snowpack in the Sierra Nevada?|journal=Monthly Weather Review|volume=140|issue=2|pages=325–342|doi=10.1175/MWR-D-11-00087.1|issn=0027-0644|bibcode=2012MWRv..140..325G|s2cid=53640141 |doi-access=free}}</ref><ref name=":2">{{Cite journal|last1=Guan|first1=Bin|last2=Waliser|first2=Duane E.|date=2015-12-27|title=Detection of atmospheric rivers: Evaluation and application of an algorithm for global studies|journal=Journal of Geophysical Research: Atmospheres  |volume=120 |issue=24 |pages=2015JD024257 |doi=10.1002/2015JD024257|issn=2169-8996|bibcode=2015JGRD..12012514G|doi-access=free}}</ref>

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."<ref name="agupubs_Curry_20190122"/>

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 rain|orographic precipitation]], a key factor in the production of intense rainfall and subsequent flooding.<ref name=":2" />

===Scale===
{| class="wikitable mw-collapsible collapsed floatright" style="width:25em; font-size:90%;"
|+Atmospheric river categories<ref name=AR-scale/>
|-
! Cat !! Strength !! Impact !! Max. IVT{{efn|Maximum vertically integrated water vapor transport, 3-hour average, units of <math>\frac{kg}{m^2 \cdot s}</math>}}!! Duration
|-
! style="font-size:125%;" rowspan=2 | 1
|rowspan=2 | Weak 
|rowspan=2 | Primarily beneficial
| style="text-align:right;" | ≥500–750
| style="text-align:right;" | <24 hours
|-
| style="text-align:right;" | ≥250–500
| style="text-align:right;" | 24–48 hours
|-
! style="font-size:125%;" rowspan=3| 2
|rowspan=3| Moderate 
|rowspan=3 | Mostly beneficial, also hazardous
| style="text-align:right;" | ≥750–1000
| style="text-align:right;" | <24 hours
|-
| style="text-align:right;" | ≥500–750
| style="text-align:right;" | 24–48 hours
|-
| style="text-align:right;" | ≥250–500
| style="text-align:right;" | >48 hours
|-
! style="font-size:125%;" rowspan=3| 3
|rowspan=3| Strong 
|rowspan=3 | Balance of beneficial and hazardous
| style="text-align:right;" | ≥1000–1250
| style="text-align:right;" | <24 hours
|-
| style="text-align:right;" | ≥750–1000
| style="text-align:right;" | 24–48 hours
|-
| style="text-align:right;" | ≥500–750
| style="text-align:right;" | >48 hours
|-
! style="font-size:125%;" rowspan=3| 4
|rowspan=3| Extreme 
|rowspan=3 | Mostly hazardous, also beneficial
| style="text-align:right;" | ≥1250
| style="text-align:right;" | <24 hours
|-
| style="text-align:right;" | ≥1000–1250
| style="text-align:right;" | 24-48 hours
|-
| style="text-align:right;" | ≥750–1000
| style="text-align:right;" | >48 hours
|-
! style="font-size:125%;" rowspan=2| 5
|rowspan=2| Exceptional 
|rowspan=2 | Primarily hazardous
| style="text-align:right;" | ≥1250
| style="text-align:right;" | 24–48 hours
|-
| style="text-align:right;" | ≥1000
| style="text-align:right;" | >48 hours
|-
| colspan=5 | '''Notes'''<br/>{{notelist}}
|}
The [https://cw3e.ucsd.edu/ 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. The scale was developed by [[F. Martin Ralph]], director of CW3E, who collaborated with [[Jonathan Rutz]] from the [[National Weather Service]] and other experts.<ref name=CW3E-scale>{{cite web |url=http://cw3e.ucsd.edu/CW3E-Releases-New-Scale-to-Characterize-Strength-and-Impacts-of-Atmospheric-Rivers/ |title=CW3E Releases New Scale to Characterize Strength and Impacts of Atmospheric Rivers |date=February 5, 2019 |publisher=Center for Western Weather and Water Extremes |access-date=16 February 2019}}</ref> 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.<ref name=AR-scale>{{cite journal |doi=10.1175/BAMS-D-18-0023.1 |title=A Scale to Characterize the Strength and Impacts of Atmospheric Rivers |author1=Ralph, F. Martin |author2=Rutz, Jonathan J. |author3=Cordeira, Jason M. |author4=Dettinger, Michael |author5=Anderson, Michael |author6=Reynolds, David |author7=Schick, Lawrence J. |author8=Smallcomb, Chris |date=February 2019 |journal=Bulletin of the American Meteorological Society|volume=100 |issue=2 |pages=269–289 |bibcode=2019BAMS..100..269R |s2cid=125322738 |doi-access=free }}</ref>

Examples of different atmospheric river categories include the following historical storms:<ref name=CW3E-scale/><ref name=AR-scale-PR>{{cite press release |url=https://scripps.ucsd.edu/news/new-scale-characterize-strength-and-impacts-atmospheric-river-storms |title=New Scale to Characterize Strength and Impacts of Atmospheric River Storms |date=February 5, 2019 |publisher=Scripps Institute of Oceanography at the University of California, San Diego |access-date=16 February 2019}}</ref>
# 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&nbsp;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.<ref name=AR-scale-PR/>

''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."<ref>''[https://twitter.com/CW3E_Scripps/status/1532884785479049216 03 June 2022 tweet from CW3E]''. {{Twitter|id=CW3E_Scripps}}. Retrieved 05 June 2022.</ref>

==Impacts==
Atmospheric rivers have a central role in the global [[water cycle]]. 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.<ref name="mwr98" /> Atmospheric rivers are also known to contribute to about 22% of total global runoff.<ref name=":3">{{Cite journal|last1=Paltan|first1=Homero|last2=Waliser|first2=Duane|last3=Lim|first3=Wee Ho|last4=Guan|first4=Bin|last5=Yamazaki|first5=Dai|last6=Pant|first6=Raghav|last7=Dadson|first7=Simon|date=2017-10-25|title=Global Floods and Water Availability Driven by Atmospheric Rivers|journal=Geophysical Research Letters|language=en|volume=44|issue=20|pages=10,387–10,395|doi=10.1002/2017gl074882|issn=0094-8276|bibcode=2017GeoRL..4410387P|url=https://ora.ox.ac.uk/objects/uuid:310059c0-a387-49de-bdff-a56b73672202|doi-access=free}}</ref>

They are also the major cause of extreme [[Precipitation (meteorology)|precipitation]] events that cause severe [[flood]]ing in many mid-latitude, westerly coastal regions of the world, including the west coast of North America,<ref name="neiman2010">{{cite conference|first=Paul J. |last=Neiman |date=2009-06-08 |title=Landfalling Impacts of Atmospheric Rivers: From Extreme Events to Long-term Consequences |url=http://www.fs.fed.us/psw/mtnclim/talks/pdf/Neiman_Talk2010.pdf |conference=The 2010 Mountain Climate Research Conference |conference-url=http://www.fs.fed.us/psw/mtnclim/ |display-authors=etal }}{{dead link|date=October 2016 |bot=InternetArchiveBot |fix-attempted=yes }}</ref><ref name="mwr08">{{cite journal|last=Neiman|first=Paul J.|title=Diagnosis of an Intense Atmospheric River Impacting the Pacific Northwest: Storm Summary and Offshore Vertical Structure Observed with COSMIC Satellite Retrievals|journal=Monthly Weather Review|year=2008|volume=136|issue=11|pages=4398–4420|doi=10.1175/2008MWR2550.1|url=http://tenaya.ucsd.edu/~dettinge/neiman_cosmic08.pdf|bibcode=2008MWRv..136.4398N|display-authors=etal|access-date=2010-12-15|archive-url=https://web.archive.org/web/20100629082635/http://tenaya.ucsd.edu/~dettinge/neiman_cosmic08.pdf|archive-date=2010-06-29|url-status=dead}}</ref><ref name="jmet08">{{cite journal|last=Neiman|first=Paul J.|title=Meteorological Characteristics and Overland Precipitation Impacts of Atmospheric Rivers Affecting the West Coast of North America Based on Eight Years of SSM/I Satellite Observations|journal=Journal of Hydrometeorology|year=2008|volume=9|issue=1|pages=22–47|doi=10.1175/2007JHM855.1|url=http://tenaya.ucsd.edu/~dettinge/Neiman_Ar-JHM08.pdf|bibcode=2008JHyMe...9...22N|display-authors=etal|access-date=2010-12-15|archive-url=https://web.archive.org/web/20100629080711/http://tenaya.ucsd.edu/~dettinge/Neiman_Ar-JHM08.pdf|archive-date=2010-06-29|url-status=dead}}</ref><ref name="grl06">{{cite journal|last=Ralph|first=F. Martin|title=Flooding on California's Russian River: Role of atmospheric rivers|journal=Geophys. Res. Lett.|year=2006|volume=33|issue=13|pages=L13801|doi=10.1029/2006GL026689|url=http://tenaya.ucsd.edu/~dettinge/atmos_rivers.pdf|bibcode=2006GeoRL..3313801R|s2cid=14641695 |display-authors=etal|access-date=2010-12-15|archive-url=https://web.archive.org/web/20100629123535/http://tenaya.ucsd.edu/~dettinge/atmos_rivers.pdf|archive-date=2010-06-29|url-status=dead}}</ref> Western Europe,<ref>{{cite web|title=Atmospheric river of moisture targets Britain and Ireland|url=http://cimss.ssec.wisc.edu/goes/blog/archives/3838|work=CIMSS Satellite Blog|date=November 19, 2009}}</ref><ref>{{cite journal|last=Stohl|first=A. |author2=Forster, C. |author3=Sodermann, H. |title=Remote sources of water vapor forming precipitation on the Norwegian west coast at 60°N–a tale of hurricanes and an atmospheric river|journal=Journal of Geophysical Research|date=March 2008|volume=113|issue=D5 |pages=n/a |url=https://elib.dlr.de/48643/1/2007JD009006.pdf| doi = 10.1029/2007jd009006 |bibcode=2008JGRD..113.5102S}}<!--|access-date=10 July 2012--></ref><ref>{{cite journal|last=Lavers|first=David A|author2=R. P. Allan |author3=E. F. Wood |author4=G. Villarini |author5=D. J. Brayshaw |author6=A. J. Wade |title=Winter floods in Britain are connected to atmospheric rivers|journal=[[Geophysical Research Letters]]|date=6 December 2011|volume=38|issue=23|pages=n/a|doi=10.1029/2011GL049783|url=http://www.met.reading.ac.uk/~sgs02rpa/PAPERS/Lavers11GRL.pdf|access-date=12 August 2012|bibcode = 2011GeoRL..3823803L |citeseerx=10.1.1.722.4841|s2cid=12816081 }}</ref> the west coast of [[North Africa]],<ref name="sci06" /> the Iberian Peninsula, Iran<ref name="Dezfuli E394–E400">{{Cite journal|last=Dezfuli|first=Amin|date=2019-12-27|title=Rare atmospheric river caused record floods across the Middle East|journal=Bulletin of the American Meteorological Society|volume=101|issue=4|pages=E394–E400|doi=10.1175/BAMS-D-19-0247.1|issn=0003-0007|doi-access=free}}</ref> and New Zealand.<ref name=":3" /> 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.<ref name=":3" />

===United States===
[[File:Atmospheric River GOES WV 20101220.1200.goes11.vapor.x.pacus.x.jpg|thumb|Water vapor imagery of the eastern Pacific Ocean from the [[GOES 11]] satellite, showing [[December 2010 North American blizzard#Meteorological history|a large atmospheric river]] aimed across California in December 2010. This particularly intense storm system produced as much as {{convert|26|in|mm|abbr=on}} of precipitation in California and up to {{convert|17|ft|m|abbr=on}} of snowfall in the Sierra Nevada during December 17–22, 2010.]]

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.<ref name=":1" /> 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.<ref>{{Cite journal|last=Dettinger|first=Michael D.|date=2013-06-28|title=Atmospheric Rivers as Drought Busters on the U.S. West Coast|journal=Journal of Hydrometeorology|volume=14|issue=6|pages=1721–1732|doi=10.1175/JHM-D-13-02.1|issn=1525-755X|bibcode=2013JHyMe..14.1721D|s2cid=2030208 |doi-access=free}}</ref> The Fourth [[National Climate Assessment]] (NCA) report, released by the [[U.S. Global Change Research Program]] (USGCRP) on November 23, 2018<ref name="CNN_Christensen_2018">{{cite news |url=https://www.cnn.com/2018/11/23/health/climate-change-report-bn/index.html |title=Climate change will shrink US economy and kill thousands, government report warns |first1=Jen |last1=Christensen |first2=Michael |last2=Nedelman |newspaper=CNN |date=November 23, 2018 |access-date=November 23, 2018}}</ref> 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."<ref name=":0" /><ref name="grl06" /><ref name="NCA2018_Chap2">{{citation|series=National Climate Assessment (NCA) |title=Chapter 2: Our Changing Climate|date=November 23, 2018|url=https://nca2018.globalchange.gov/chapter/2/|format=PDF|publisher=USGCRP|access-date=November 23, 2018|location=Washington, DC}}</ref>

The USGCRP team of thirteen federal agencies—the [[United States Department of Agriculture|DOA]], [[United States Department of Commerce|DOC]], [[United States Department of Defense|DOD]], [[United States Department of Energy|DOE]], [[United States Department of Health and Human Services|HHS]], [[United States Department of the Interior|DOI]], [[United States Department of State|DOS]], [[United States Department of Transportation|DOT]], [[Environmental Protection Agency|EPA]], [[National Aeronautics and Space Administration|NASA]], [[National Science Foundation|NSF]], [[Smithsonian Institution]], and the [[Agency for International Development|USAID]]—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."<ref name=":0" /><ref name= "CNN_Christensen_2018"/><ref name="NCA_IV_Wehner_2017">{{cite report |last1=Wehner |first1=M. F. |first2=J. R. |last2=Arnold |first3=T. |last3=Knutson |first4=K. E. |last4=Kunkel |first5=A. N. |last5=LeGrande |date=2017 |title= Droughts, Floods, and Wildfires |series=Climate Science Special Report: Fourth National Climate Assessment |volume=1 |editor1-last=Wuebbles  |editor1-first=D. J. |editor2-first=D. W. |editor2-last=Fahey |editor3-first=K. A. |editor3-last=Hibbard |editor4-first=D. J. |editor4-last=Dokken |editor5-first=B. C. |editor5-last=Stewart |editor6-first=T. K. |editor6-last=Maycock |publisher=U.S. Global Change Research Program |location=Washington, DC |pages=231–256 |doi= 10.7930/J0CJ8BNN|doi-access=free }}</ref><ref>Warner, M. D., C. F. Mass, and E. P. Salathé Jr., 2015: Changes in winter atmospheric rivers along the North American West Coast in CMIP5 climate models. Journal of Hydrometeorology, 16 (1), 118–128. doi:10.1175/JHM-D-14-0080.1.</ref><ref>Gao, Y., J. Lu, L. R. Leung, Q. Yang, S. Hagos, and Y. Qian, 2015: Dynamical and thermodynamical modulations on future changes of landfalling atmospheric rivers over western North America. Geophysical Research Letters, 42 (17), 7179–7186. doi:10.1002/2015GL065435.</ref>

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.<ref name="AMS_Neiman_2011">{{cite journal |last1=Neiman |first1=Paul. J. |first2=L. J. |last2=Schick |first3=F. M. |last3=Ralph |first4=M. |last4=Hughes |first5=G. A. |last5=Wick |date=December 2011 |title=Flooding in western Washington: The connection to atmospheric rivers. |journal= Journal of Hydrometeorology|volume=12 |issue=6 |pages=1337–1358 |doi=10.1175/2011JHM1358.1 |bibcode=2011JHyMe..12.1337N |doi-access=free }}</ref>

According to a May 14, 2019 article in [[San Jose, California]]'s ''[[The Mercury News]]'', 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.<ref name="mercurynews_Rogers_20190514">{{Cite news| last = Paul Rogers| title = Rare "atmospheric river" storms to soak California this week| work = [[The Mercury News]]| location = [[San Jose, California]]| access-date = 2019-05-15| date = 2019-05-14| url = https://www.mercurynews.com/2019/05/14/rare-atmospheric-river-storms-to-soak-california-this-week/}}</ref><ref name=sfc>{{cite news | title=Storms that cost the West billions in damage |author=Kurtis Alexander |newspaper=San Francisco Chronicle |page=A1 |date=December 5, 2019}}</ref> [[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."<ref>{{Cite news| last = Jill Cowan| title = Atmospheric Rivers Are Back. That's Not a Bad Thing| work = The New York Times| date = 2019-05-15| url = https://www.nytimes.com/2019/05/15/us/atmospheric-river-climate-change-california.html?smtyp=cur&smid=tw-nytnational}}</ref>

Atmospheric rivers have caused an average of $1.1 billion in damage annually, much of it occurring in [[Sonoma County, California|Sonoma County]], California, according to a December 2019 study by the [[Scripps Institution of Oceanography|Scripps Institution on Oceanography]] at [[University of California, San Diego|UC San Diego]] and the [[US Army Corps of Engineers]],<ref>{{cite journal |last1=Corringham |first1=Thomas W. |last2=Ralph |first2=F. Martin |last3=Gershunov |first3=Alexander |last4=Cayan |first4=Daniel R. |last5=Talbot |first5=Cary A. |title=Atmospheric Rivers Drive Flood Damages in the Western United States |journal=Science Advances |date=December 4, 2019 |volume=5 |issue=12 |pages=eaax4631 |doi=10.1126/sciadv.aax4631|pmid=31840064 |pmc=6892633 |bibcode=2019SciA....5.4631C }}</ref> which analyzed data from the [[National Flood Insurance Program]] and the [[National Weather Service]]. 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 [[Floodplain|flood plain]]. These counties were:<ref name=sfc />
{{col-list|colwidth=15em|
*Snohomish County, WA ($1.2 billion)
*King County, WA ($2 billion)
*Pierce County, WA ($900 million)
*Lewis County, WA ($3 billion)
*Cowlitz County WA ($500 million)
*Columbia County, OR ($700 million)
*Clackamas, County, OR ($900 million)
*Washoe County, NV ($1.3 billion)
*Placer County, CA ($800 million)
*Sacramento County, CA ($1.7 billion)
*Napa County, CA ($1.3 billion)
*Sonoma County, CA ($5.2 billion)
*Marin County, CA ($2.2 billion)
*Santa Clara County, CA ($1 billion)
*Monterey County, CA ($1.3 billion)
*Los Angeles County, CA ($2.7 billion)
*Riverside County, CA ($500 million)
*Orange County, CA ($800 million)
*San Diego County, CA ($800 million)
*Maricopa County, AZ ($600 million) 
}}

===Canada===
According to a January 22, 2019 article in ''[[Geophysical Research Letters]]'', the [[Fraser River Basin]] (FRB), a "snow-dominated watershed"<ref group="Note">According to the Curry et al article, "Snow-dominated watersheds are bellwethers of climate change."</ref> in British Columbia, is exposed to landfalling ARs, originating over the tropical Pacific Ocean that bring "sustained, heavy precipitation" throughout the winter months.<ref name="agupubs_Curry_20190122">{{Cite journal| issn = 1944-8007| volume = 46| issue = 3| pages = 1651–1661| last1 = Curry| first1 = Charles L.| last2 = Islam| first2 = Siraj U.| last3 = Zwiers| first3 = F. W.| last4 = Déry| first4 = Stephen J.| title = Atmospheric Rivers Increase Future Flood Risk in Western Canada's Largest Pacific River| journal = [[Geophysical Research Letters]]| date = January 22, 2019|doi=10.1029/2018GL080720| bibcode = 2019GeoRL..46.1651C| s2cid = 134391178}}</ref> 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."<ref name="agupubs_Curry_20190122"/>

In November 2021, [[November 2021 Pacific Northwest floods|massive flooding]] in the Fraser River Basin near Vancouver was attributed to a series of atmospheric rivers.<ref>{{cite web | title = Deluge to take a pause in B.C. before next atmospheric river arrives | website = [[The Weather Network]] | date = November 28, 2021 | url = https://www.theweathernetwork.com/ca/news/article/alerts-in-place-as-atmospheric-rivers-threaten-flood-plagued-british-columbia | access-date = November 29, 2021}}</ref>

=== 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 [[2019 Iran floods|floods of March 2019 in Iran]] that damaged one-third of the country's infrastructures and killed 76 people.<ref name="Dezfuli E394–E400"/> 

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&nbsp;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]], [[Euphrates]], [[Karun]] and [[Karkheh River|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, [[Australian northwest cloudbands|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]]).<ref>{{cite web|url=http://www.bom.gov.au/watl/about-weather-and-climate/australian-climate-influences.shtml?bookmark=nwcloudband|title=Northwest cloudbands|publisher=[[Bureau of Meteorology]]|date=5 June 2013|access-date=11 August 2020}}</ref><ref>{{cite web|url=http://www.bom.gov.au/watl/about-weather-and-climate/australian-climate-influences.shtml?bookmark=iod|title=Indian Ocean|publisher=[[Bureau of Meteorology]]|access-date=11 August 2020}}</ref> Atmospheric rivers also form in the waters to the east and south of Australia and are most common during the warmer months.<ref>{{cite journal | last1=Guan | first1=Bin | last2=Waliser | first2=Duane | date=2015-11-28 | title=Detection of Atmospheric Rivers: Evaluation and Application of an Algorithm for Global Studies | journal= Journal of Geophysical Research: Atmospheres| volume=120 | issue=24 | pages=12514–12535 | doi=10.1002/2015JD024257| bibcode=2015JGRD..12012514G | s2cid=131498684 | doi-access=free }}</ref>

=== Europe ===
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.<ref>{{Cite journal|last1=Lavers|first1=David A.|last2=Villarini|first2=Gabriele|date=2013-06-28|title=The nexus between atmospheric rivers and extreme precipitation across Europe: ARS AND EXTREME EUROPEAN PRECIPITATION|url=http://doi.wiley.com/10.1002/grl.50636|journal=Geophysical Research Letters|language=en|volume=40|issue=12|pages=3259–3264|doi=10.1002/grl.50636|s2cid=129890209 }}</ref>

==Satellites and sensors==
According to a 2011 ''[[Eos (magazine)|Eos]]'' magazine article<ref group="Note">''[[Eos (magazine)|Eos]], Transactions'' is published weekly by the [[American Geophysical Union]] and covers topics related to [[earth science]].</ref> 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). 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."<ref name="EoS">{{Cite magazine| magazine = [[Eos (magazine)|Eos, Transactions, American Geophysical Union]]| doi = 10.1029/2011EO320001| volume = 92| issue = 32| pages = 265–272| last1 = F. M. Ralph| last2 = M. D. Dettinger| title = Storms, Floods, and the Science of Atmospheric Rivers| publisher = [[John Wiley & Sons]] for the [[American Geophysical Union]] (AGU)| date = August 9, 2011| url = http://tenaya.ucsd.edu/~dettinge/2011EO320001.pdf| location = [[Washington, DC]]| access-date = May 15, 2019| archive-date = May 17, 2019| archive-url = https://web.archive.org/web/20190517063029/http://tenaya.ucsd.edu/~dettinge/2011EO320001.pdf| url-status = dead}}</ref><ref name="EoS_about">{{cite web|title=Eos, Transactions, American Geophysical Union|url=http://www.speciation.net/Database/Journals/Eos-Transactions-American-Geophysical-Union-;i1894|publisher=evisa|access-date=25 March 2016}}</ref>

==See also==
* [[Tropical upper tropospheric trough]], 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]]

==Notes==
{{reflist|group="Note"}}

==References==
{{reflist|2}}

==Further reading==
* {{cite journal |title=When It Rains, It Pours: Historic Drought and Atmospheric Rivers |author=Les Rowntree |date= July 27, 2015 |journal=Bay Nature Magazine |url=http://baynature.org/article/when-it-rains-it-pours/ |access-date=November 9, 2016}} 
* [https://climate.nasa.gov/news/2740/climate-change-may-lead-to-bigger-atmospheric-rivers  Climate change may lead to bigger atmospheric rivers] - [[NASA]]

==External links==
{{Wikiquote}}
*[https://earth.nullschool.net/#current/wind/surface/level/overlay=precip_3hr/winkel3/ Current map of predicted global precipitation for the next three hours]
*[https://www.cbsnews.com/video/cbs-news-joins-hurricane-hunters-flight-over-atmospheric-river/ CBS News segment; Jan. 31, 2024]: <small>CBS News environmental reporter [[Ben Tracy]] joined a team of scientists from [[NOAA]] as they dropped electronic monitoring instruments into an atmospheric river during a high-altitude reconnaissance flight over the Pacific Ocean.</small>

{{Authority control}}

[[Category:Atmospheric dynamics]]
[[Category:Atmospheric circulation]]
[[Category:Clouds, fog and precipitation]]
[[Category:Meteorological phenomena]]
[[Category:Severe weather and convection]]