|Part of the nature series|
An atmospheric river (AR) is a narrow corridor or filament of concentrated moisture in the atmosphere. 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.Pineapple Express storms are the most commonly represented and recognized type of atmospheric rivers; they are given the name due to the warm water vapor plumes originating over the Hawaiian tropics that follow a path towards California.
An atmosphere is a layer or a set of layers of gases surrounding a planet or other material body, that is held in place by the gravity of that body. An atmosphere is more likely to be retained if the gravity it is subject to is high and the temperature of the atmosphere is low.
Water vapor, water vapour or aqueous vapor is the gaseous phase of water. It is one state of water within the hydrosphere. Water vapor can be produced from the evaporation or boiling of liquid water or from the sublimation of ice. Unlike other forms of water, water vapor is invisible. Under typical atmospheric conditions, water vapor is continuously generated by evaporation and removed by condensation. It is less dense than air and triggers convection currents that can lead to clouds.
A weather front is a boundary separating two masses of air of different densities, and is the principal cause of meteorological phenomena outside the tropics. In surface weather analyses, fronts are depicted using various colored triangles and half-circles, depending on the type of front. The air masses separated by a front usually differ in temperature and humidity.
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.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 the Earth's largest river, the Amazon River. There are typically 3–5 of these narrow plumes present within a hemisphere at any given time.
The Massachusetts Institute of Technology (MIT) is a private research university in Cambridge, Massachusetts. Founded in 1861 in response to the increasing industrialization of the United States, MIT adopted a European polytechnic university model and stressed laboratory instruction in applied science and engineering. It has since played a key role in the development of many aspects of modern science, engineering, and mathematics, and is widely known for its innovation and academic strength, making it one of the most prestigious institutions of higher learning in the world. The Institute is a land-grant, sea-grant, and space-grant university, with an urban campus that extends more than a mile alongside the Charles River.
The Amazon River in South America is the largest river by discharge volume of water in the world, and by some definitions it is the longest.
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 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" that cause rainfall throughout the winter months."
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 is Noah Diffenbaugh.
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 (IWV). In addition IVT is more directly attributed to orographic precipitation, a key factor in the production of intense rainfall and subsequent flooding.For instance the water vapor image to the left shows two rivers on 5 December 2015: the first, stretching from the Caribbean to the United Kingdom, caused by Storm Desmond, and the second originating from the Philippines is crossing Pacific Ocean to the west coast of North America.
The Caribbean is a region of The Americas that consists of the Caribbean Sea, its islands and the surrounding coasts. The region is southeast of the Gulf of Mexico and the North American mainland, east of Central America, and north of South America.
The United Kingdom (UK), officially the United Kingdom of Great Britain and Northern Ireland, and sometimes referred to as Britain, is a sovereign country located off the north-western coast of the European mainland. The United Kingdom includes the island of Great Britain, the north-eastern part of the island of Ireland, and many smaller islands. Northern Ireland is the only part of the United Kingdom that shares a land border with another sovereign state, the Republic of Ireland. Apart from this land border, the United Kingdom is surrounded by the Atlantic Ocean, with the North Sea to the east, the English Channel to the south and the Celtic Sea to the south-west, giving it the 12th-longest coastline in the world. The Irish Sea lies between Great Britain and Ireland. With an area of 242,500 square kilometres (93,600 sq mi), the United Kingdom is the 78th-largest sovereign state in the world. It is also the 22nd-most populous country, with an estimated 66.0 million inhabitants in 2017.
Storm Desmond was an extratropical cyclone and fourth named storm of the 2015–16 UK and Ireland windstorm season, notable for directing a plume of moist air, known as an atmospheric river, which brought record amounts of orographic rainfall to upland areas of northern Atlantic Europe and subsequent major floods.
|2||Moderate||Mostly beneficial, also hazardous||≥500-750|
|3||Strong||Balance of beneficial and hazardous||≥750-1000|
|4||Extreme||Mostly hazardous, also beneficial||≥1000-1250|
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. The scale was developed by F. Martin Ralph, director of CW3E, who collaborated with Jonathan Rutz from the National Weather Service 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.
The Scripps Institution of Oceanography in La Jolla, California, founded in 1903, is one of the oldest and largest centers for ocean and Earth science research, public service, undergraduate and graduate training in the world. Hundreds of ocean and Earth scientists conduct research with the aid of oceanographic research vessels and shorebased laboratories. Its Old Scripps Building is a U.S. National Historic Landmark. SIO is a division of the University of California San Diego (UCSD). The public explorations center of the institution is the Birch Aquarium at Scripps. Since becoming part of the University of California in 1912, the institution has expanded its scope to include studies of the physics, chemistry, geology, biology, and climate of Earth.
The National Weather Service (NWS) is an agency of the United States federal government that is tasked with providing weather forecasts, warnings of hazardous weather, and other weather-related products to organizations and the public for the purposes of protection, safety, and general information. It is a part of the National Oceanic and Atmospheric Administration (NOAA) branch of the Department of Commerce, and is headquartered in Silver Spring, Maryland, within the Washington metropolitan area. The agency was known as the United States Weather Bureau from 1890 until it adopted its current name in 1970.
Examples of different atmospheric river categories include the following historical storms:
Typically, the Oregon coast averages one Cat 4 atmospheric river (AR) each year; Washington state averages one Cat 4 AR every two years; the 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.
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 the Earth's circumference.Atmospheric rivers are also known to contribute to about 22% of total global runoff.
They also are the major cause of extreme precipitation events that cause severe flooding 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, 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.
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 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 (NCA) report, released by the U.S. Global Change Research Program (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, DOD, DOE, HHS, DOI, DOS, DOT, EPA, NASA, NSF, Smithsonian Institution, and the 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."
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.
The front cover of the NCA4 report features a natural-color NASA image of conditions over the northeastern Pacific on February 20, 2017. The report said that this AR brought a "stunning" end to the American West's 5-year drought with "some parts of California received nearly twice as much rain in a single deluge as normally falls in the preceding 5 months (October–February)". NASA Earth Observatory's Jesse Allen created the front cover visualization with the Visible Infrared Imaging Radiometer Suite (VIIRS) data on the Suomi National Polar-orbiting Partnership (NPP) satellite.
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.University of California at San Diego's Center for Western Weather and Water Extremes's director Marty Ralph, who is one of the United State's 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 river, 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."
According to a January 22, 2019 article in Geophysical Research Letters , the Fraser River Basin (FRB), a "snow-dominated watershed"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."
According to a 2011 Eos magazine articleby 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 ARs. 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 (IWV) over the Earth’s oceans."
El Niño is the warm phase of the El Niño–Southern Oscillation (ENSO) and is associated with a band of warm ocean water that develops in the central and east-central equatorial Pacific, including the area off the Pacific coast of South America. The ENSO is the cycle of warm and cold sea surface temperature (SST) of the tropical central and eastern Pacific Ocean. El Niño is accompanied by high air pressure in the western Pacific and low air pressure in the eastern Pacific. El Niño phases are known to occur close to four years, however, records demonstrate that the cycles have lasted between two and seven years. During the development of El Niño, rainfall develops between September–November. The cool phase of ENSO is La Niña, with SSTs in the eastern Pacific below average, and air pressure high in the eastern Pacific and low in the western Pacific. The ENSO cycle, including both El Niño and La Niña, causes global changes in temperature and rainfall.
La Niña is a coupled ocean-atmosphere phenomenon that is the colder counterpart of El Niño, as part of the broader El Niño–Southern Oscillation climate pattern. The name La Niña originates from Spanish, meaning "the little girl", analogous to El Niño meaning "the little boy". It has also in the past been called anti-El Niño, and El Viejo. During a period of La Niña, the sea surface temperature across the equatorial Eastern Central Pacific Ocean will be lower than normal by 3 to 5°C. An appearance of La Niña persists for at least five months. It has extensive effects on the weather across the globe, particularly in North America, even affecting the Atlantic and Pacific hurricane seasons.
In meteorology, precipitation is any product of the condensation of atmospheric water vapor that falls under gravity. The main forms of precipitation include drizzle, rain, sleet, snow, graupel and hail. Precipitation occurs when a portion of the atmosphere becomes saturated with water vapor, so that the water condenses and "precipitates". Thus, fog and mist are not precipitation but suspensions, because the water vapor does not condense sufficiently to precipitate. Two processes, possibly acting together, can lead to air becoming saturated: cooling the air or adding water vapor to the air. Precipitation forms as smaller droplets coalesce via collision with other rain drops or ice crystals within a cloud. Short, intense periods of rain in scattered locations are called "showers."
El Niño–Southern Oscillation (ENSO) is an irregularly periodic variation in winds and sea surface temperatures over the tropical eastern Pacific Ocean, affecting the climate of much of the tropics and subtropics. The warming phase of the sea temperature is known as El Niño and the cooling phase as La Niña. The Southern Oscillation is the accompanying atmospheric component, coupled with the sea temperature change: El Niño is accompanied by high air surface pressure in the tropical western Pacific and La Niña with low air surface pressure there. The two periods last several months each and typically occur every few years with varying intensity per period.
The Pacific Decadal Oscillation (PDO) is a robust, recurring pattern of ocean-atmosphere climate variability centered over the mid-latitude Pacific basin. The PDO is detected as warm or cool surface waters in the Pacific Ocean, north of 20°N. Over the past century, the amplitude of this climate pattern has varied irregularly at interannual-to-interdecadal time scales. There is evidence of reversals in the prevailing polarity of the oscillation occurring around 1925, 1947, and 1977; the last two reversals corresponded with dramatic shifts in salmon production regimes in the North Pacific Ocean. This climate pattern also affects coastal sea and continental surface air temperatures from Alaska to California.
The Madden–Julian oscillation (MJO) is the largest element of the intraseasonal variability in the tropical atmosphere. It was discovered in 1971 by Roland Madden and Paul Julian of the American National Center for Atmospheric Research (NCAR). It is a large-scale coupling between atmospheric circulation and tropical deep atmospheric convection. Unlike a standing pattern like the El Niño–Southern Oscillation (ENSO), the Madden–Julian oscillation is a traveling pattern that propagates eastward, at approximately 4 to 8 m/s, through the atmosphere above the warm parts of the Indian and Pacific oceans. This overall circulation pattern manifests itself most clearly as anomalous rainfall.
In hydrology, moisture recycling or precipitation recycling refer to the process by which a portion of the precipitated water that evapotranspired from a given area contributes to the precipitation over the same area. Moisture recycling is thus a component of the hydrologic cycle. The ratio of the locally derived precipitation to total precipitation is known as the recycling ratio, : .
Air stagnation is a phenomenon which occurs when an air mass remains over an area for an extended period. Stagnation events strongly correlates with poor air quality. Due to light winds and lack of precipitation, pollutants cannot be cleared from the air, either gaseous or particulate. Subsidence produced directly under the subtropical ridge can lead to a buildup of particulates in urban areas under the ridge, leading to widespread haze. If the low level relative humidity rises towards 100 percent overnight, fog can form. In the United States, the National Weather Service issues an Air Stagnation Advisory when these conditions are likely to occur.
John Adrian Pyle is an English atmospheric scientist, Director of the Centre for Atmospheric Science in Cambridge, England. He is a Professor in the Department of Chemistry at the University of Cambridge, and since 2007 has held the 1920 Chair of Physical Chemistry in the Chemistry Department. He is also a Fellow of the Royal Society and of St Catharine's College, Cambridge.
The cumulonimbus flammagenitus cloud (CbFg), also known as the pyrocumulonimbus cloud, is a type of cumulonimbus cloud that forms above a source of heat, such as a wildfire, and may sometimes even extinguish the fire that formed it. It is the most extreme manifestation of a flammagenitus cloud. According to the American Meteorological Society’s Glossary of Meteorology, a flammagenitus is "a cumulus cloud formed by a rising thermal from a fire, or enhanced by buoyant plume emissions from an industrial combustion process." Analogous to the meteorological distinction between cumulus and cumulonimbus, the cumulonimbus flammagenitus is a fire-aided or –caused convective cloud, like a flammagenitus, but with considerable vertical development. The CbFg reaches the upper troposphere or even lower stratosphere and may involve precipitation, hail, lightning, extreme low-level winds, and in some cases even tornadoes.
The Atlantic Multidecadal Oscillation (AMO) is a climate cycle that affects the sea surface temperature (SST) of the North Atlantic Ocean based on different modes on multidecadal timescales. While there is some support for this mode in models and in historical observations, controversy exists with regard to its amplitude, and in particular, the attribution of sea surface temperature change to natural or anthropogenic causes, especially in tropical Atlantic areas important for hurricane development. The Atlantic multidecadal oscillation is also connected with shifts in hurricane activity, rainfall patterns and intensity, and changes in fish populations.
The Indian Ocean Dipole (IOD), also known as the Indian Niño, is an irregular oscillation of sea-surface temperatures in which the western Indian Ocean becomes alternately warmer and then colder than the eastern part of the ocean.
Peter A. Stott is a climate scientist who leads the Climate Monitoring and Attribution team of the Hadley Centre for Climate Prediction and Research at the Met Office in Exeter, UK. He is an expert on anthropogenic and natural causes of climate change.
Polar amplification is the phenomenon that any change in the net radiation balance tends to produce a larger change in temperature near the poles than the planetary average. On a planet with an atmosphere that can restrict longwave radiation to space, surface temperatures will be warmer than a simple planetary equilibrium temperature calculation would predict. Where the atmosphere or an extensive ocean is able to transport heat polewards, the poles will be warmer and equatorial regions cooler than their local net radiation balances would predict.
This article is about the physical impacts of climate change. For some of these physical impacts, their effect on social and economic systems are also described.
PERSIANN, "Precipitation Estimation from Remotely Sensed Information using Artificial Neural Networks", is a satellite-based precipitation retrieval algorithm that provides near real-time rainfall information. The algorithm uses infrared (IR) satellite data from global geosynchronous satellites as the primary source of precipitation information. Precipitation from IR images is based on statistical relationship between cloud top temperature and precipitation rates. The IR-based precipitation estimates are then calibrated using satellite microwave data available from low Earth orbit satellites. The calibration technique relies on an adaptive training algorithm that updates the retrieval parameters when microwave observations become available.
Olga Zolina is a climate scientist, member of the GEWEX (WCRP), responsible for GEWEX Radiation Panel, member of the European Geosciences Union, German Meteorological Society and the American Geophysical Union.
The "Ridiculously Resilient Ridge," sometimes shortened to "Triple R" or "RRR," is the nickname given to a persistent anticyclone that occurred over the far northeastern Pacific Ocean, causing the 2011–2017 California drought. The "Ridiculously Resilient Ridge" nickname was originally coined in December 2013 by Daniel Swain on the Weather West Blog, but has since been used widely in popular media as well as in peer-reviewed scientific literature.
A precipitationshed is the upwind ocean and land surface that contributes evaporation to a given, downwind location's precipitation. The concept has been described as an "atmospheric watershed". The concept itself rests on a broad foundation of scholarly work examining the evaporative sources of rainfall. Since its formal definition, the precipitationshed has become an element in water security studies, examinations of sustainability, and mentioned as a potentially useful tool for examining vulnerability of rainfall dependent ecosystems.
Cirrus cloud thinning is a proposed form of climate engineering. Cirrus clouds are high cold ice that, like other clouds, both reflect sunlight and absorb warming infrared radiation. However, they differ from other types of clouds in that, on average, infrared absorption outweighs sunlight reflection, resulting in a net warming effect on the climate. Therefore, thinning or removing these clouds would reduce their heat trapping capacity, resulting in a cooling effect on Earth's climate. This could be a potential tool to reduce anthropogenic global warming. Cirrus cloud thinning is an alternative category of climate engineering, in addition to solar radiation management and greenhouse gas removal.
The present‐day frequency of landfalling atmospheric rivers on the Canadian west coast is projected to increase nearly fourfold by the late 21st century, with a proportionate increase in extreme rainfall events. Our work is the first to directly investigate the impact of these “rivers in the sky” on “rivers on the land” using climate model projections. Focusing on the Fraser River Basin, Canada's largest Pacific watershed, and using a business‐as‐usual industrial emissions scenario, we show that the basin transitions from one where peak flow results from spring snowmelt to one where peak flow is often caused by extreme rainfall. Our modeling suggests that 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.