Atmospheric Rivers: key to extratropical water vapor transport

Just about any time we get a flooding event these days, some wailing uninformed opportunist jumps on the “global warming did it” bandwagon in an attempt to explain it. Those of us who have been in the weather forecasting business for years often look for more mundane and well known phenomena as the cause.

One of those is the atmospheric river, or as we often call it here in California, the “Pineapple Express”. NOAA recently created an information page and PR on the issue, and I’m providing it here for those who would like to learn more about it.

This satellite view of atmospheric rivers is key to understanding extreme precipitation events along the West Coast. (Credit: NOAA)

Atmospheric rivers are relatively long, narrow regions in the atmosphere – like rivers in the sky – that transport most of the water vapor outside of the tropics. These columns of vapor move with the weather, carrying an amount of water vapor roughly equivalent to the average flow of water at the mouth of the Mississippi River. When the atmospheric rivers make landfall, they often release this water vapor in the form of rain or snow.

Although atmospheric rivers come in many shapes and sizes, those that contain the largest amounts of water vapor and the strongest winds can create extreme rainfall and floods, often by stalling over watersheds vulnerable to flooding. These events can disrupt travel, induce mudslides and cause catastrophic damage to life and property. A well-known example is the “Pineapple Express,” a strong atmospheric river that is capable of bringing moisture from the tropics near Hawaii over to the U.S. West Coast.

Not all atmospheric rivers cause damage; most are weak systems that often provide beneficial rain or snow that is crucial to the water supply. Atmospheric rivers are a key feature in the global water cycle and are closely tied to both water supply and flood risks —particularly in the western United States.

Flooding and debris-flows.

Flooding and debris flows can occur quickly and trap or kill unsuspecting victims in their path. (Credit: NOAA)

While atmospheric rivers are responsible for great quantities of rain that can produce flooding, they also contribute to beneficial increases in snowpack. A series of atmospheric rivers fueled the strong winter storms that battered the U.S. West Coast from western Washington to southern California from Dec. 10–22, 2010, producing 11 to 25 inches of rain in certain areas. These rivers also contributed to the snowpack in the Sierras, which received 75 percent of its annual snow by Dec. 22, the first full day of winter.

NOAA research (e.g., NOAA Hydrometeorological Testbed and CalWater) uses satellite, radar, aircraft and other observations, as well as major numerical weather model improvements, to better understand atmospheric rivers and their importance to both weather and climate.

Scientific research yields important data that helps NOAA National Weather Service forecasters issue warnings for potential heavy rain and flooding in areas prone to the impacts of atmospheric rivers as many as five to seven days in advance.

Quick Overview

  • Atmospheric Rivers (AR) are relatively narrow regions in the atmosphere that are responsible for most of the horizontal transport of water vapor outside of the tropics.
  • ARs move with the weather and are present somewhere on the earth at any given time.
  • In the strongest cases ARs can create major flooding when they make land-fall.
  • On average ARs are 400-600 km wide.
  • For comparison, a strong AR transports an amount of water vapor roughly equivalent to 10-20 times the average flow of liquid water at the mouth of the Mississippi River.
  • While ARs come in many shapes and sizes, those that contain the largest amounts of water vapor, the strongest winds, and stall over watersheds vulnerable to flooding, can create extreme rainfall and floods. These events can disrupt travel, induce mud slides, and cause catastrophic damage to life and property.
  • A well-known example of a type of strong AR that can hit the U.S. west coast is the “Pineapple Express,” due to their apparent ability to bring moisture from the tropics near Hawaii to the U.S. west coast.
  • Not all ARs cause damage – most are weak, and simply provide beneficial rain or snow that is crucial to water supply.
  • In short, ARs are a primary feature in the entire global water cycle, and are tied closely to both water supply and flood risks, particularly in the Western U.S.
  • The improved understanding of ARs and their importance has emerged from roughly a decade of scientific studies that have made use of new satellite, radar, aircraft and other observations and major numerical weather model improvements.

What are they, in more scientific terms?

ARs are the water-vapor rich part of the broader warm conveyor belt (e.g., Browning, 1990; Carlson, 1991), that is found in extratropical cyclones (“storms”). They result from the action of winds associated with the storm drawing together moisture into a narrow region just ahead of the cold front where low-level winds can sometimes exceed hurricane strength. The term AR was coined in a seminal scientific paper published in 1998 by researchers Zhu and Newell at MIT (Zhu and Newell 1998). Because they found that most of the water vapor was transported in relatively narrow regions of the atmosphere (90% of the transport occurred typically in 4-5 long, narrow regions roughly 400 km wide), the term atmospheric river was used. A number of formal scientific papers have since been published building on this concept (see the publication list), and forecasters and climate researchers are beginning to apply the ideas and methods to their fields. The satellite images at right show strong ARs as seen by satellite. The advent of these specialized satellite observations have revealed ARs over the oceans and have revolutionized understanding of the global importance of ARs (more traditional satellite data available in the past could not clearly detect AR conditions). The interpretation of these satellite images, which represent only water vapor, not winds, was confirmed using NOAA research aircraft data over the Eastern Pacific Ocean and wind profilers along the coast (Ralph et al. 2004). The event shown in the image was documented by Ralph et al. (2006), which concluded this AR produced roughly 10 inches of rain in 2 days and caused a flood on the Russian River of northern California. It was also shown that all floods on the Russian River in the 7-year period of study were associated with AR conditions. As of late 2010 there have been a number of papers published on major west coast storms where the presence and importance of AR conditions have been documented. These are provided in an informal list of the “Top Ten ARs” of the last several years on the U.S. West Coast. It is now recognized that the well-known “Pineapple express,” storms (a term that has been used on the U.S. West Coast for many years) correspond to a subset of ARs, i.e., those that have a connection to the tropics near Hawaii. In some of the most extreme ARs, the water vapor transport is enhanced by the fact that they entrain (draw in) water vapor directly from the tropics (e.g., Bao et al 2006, Ralph et al. 2011).

Can we forecast atmospheric rivers?

  • National Weather Service forecasters located along the west coast are now familiar with the concept of atmospheric rivers and can identify these phenomena in current numerical forecast models. This provides them the capability to give advanced warning of potential heavy rain sometime 5 to 7 days in advance. They have also learned to monitor polar orbiter microwave satellite imagery that provides advanced warning of the presence and movement of these phenomena in the Pacific. During the last two winters, with the development of atmospheric river observatories, forecasters have been able to monitor the strength and location of these rivers as they make landfall and thus improve short-term rainfall forecasts for flash flooding. There are still challenges to predicting rainfall totals in these events as models still struggle with the details of the duration and timing of AR’s as they make landfall.

Why are ARs capable of producing extreme rainfall on the U.S. West Coast?

AR conditions are conducive to creating heavy orographic precipitation (Ralph et al., 2005; MWR) because:

  • they are rich in water vapor,
  • they are associated with strong winds that force the water vapor up mountain sides,
  • the atmospheric conditions do not inhibit upward motions (because the atmospheric static stability is nearly neutral up to about 3 km MSL, on average)
  • once the air moves upward, the water vapor condenses and can form precipitation

What is the role of atmospheric rivers in creating floods?

  • Research has shown there were 42 ARs that impacted CA during the winters from 1997 to 2006, and the resulting seven floods that occurred on the Russian River watershed northwest of San Francisco during this period were all associated with AR conditions.
  • A major flood in California, known as the “New years Day Flood” in 1997 cause over $1 Billion in damages and had a well-defined AR.
  • Less formally, ARs are known to result in an order of magnitude larger post-storm stream flow “bumps” (increases) than other California storms, in the Merced and American Rivers.
  • The Pacific Northwest also regularly experiences this type of storm. Case in point is the landfalling AR of early November 2006 that produced heavy rainfall and devastating flooding and debris flows with region-wide damage exceeding $50 million.
  • The “Top-Ten AR” list highlights additional high-impact AR events.

How are science and applications of ARs being addressed?

  • Research experiments (CalJet and PacJet) performed by NOAA in the 1998, 2001, and 2002 were conducted to better understand landfalling Pacific winter storms.
  • CalJet/PacJet led to the development of the NOAA Hydrometeorology Testbed (HMT; hmt.noaa.gov). HMT’s aim is to accelerate the development and prototyping of advanced hydrometeorological observations, models, and physical process understanding, and to foster infusion of these advances into forecasting operations of the NWS, and to support the broader user community’s needs for 21st Century precipitation information.
  • Within HMT, scientists have developed and prototyped an atmospheric river observatory (ARO) designed to further our understanding of the impact of ARs on enhancing precipitation in the coastal mountains and the high Sierra of California.
  • Studies of the potential impacts of climate change on AR characteristics is the focus on an ongoing project – CalWater that is partnering with HMT, the California Energy Commission, Scripps Institution of Oceanography, USGS and others, to explore the potential implications for flood risk and water supply.
  • Under the USGS-led Multihazards project, ARs have become the focus of an emergency preparedness scenario for California that is intended to help the region prepare for a potentially catastrophic series of ARs. The scenario is named “ARkStorm” and has developed an informational video for use with the public (http://urbanearth.gps.caltech.edu/winter-storm/).

What are the benefits of studying atmospheric rivers?

  • The community of flood control, water supply and reservoir operators of the West Coast states see ARs as a key phenomenon to understand, monitor and predict as they work to mitigate the risks of major flood events, while maintaining adequate water supply. The frequency and strength of AR events in a given region over the course of a typical west-coast wet season greatly influences the fate of droughts, floods, and many key human endeavors and ecosystems. Better coupling of climate forecasts with seasonal weather forecasts of ARs can improve water management decisions. Long-term monitoring using satellite measurements, offshore aircraft reconnaissance, and land-based atmospheric river observatories, combined with better numerical modeling, scientific progress, and the development of AR-based smart decision aids for resource managers, will enable society to be more resilient to storms and droughts, while protecting our critical ecosystems.

examples of ARs

Examples of AR events that produced extreme precipitation on the US West Coast, and exhibited spatial continuity with the tropical water vapor reservoir as seen in SSM/I satellite observations of IWV. (From Ralph et al. 2011, Mon. Weather Review) 

The color scale used in these images represents the total amount of water vapor between the ocean surface and space. The data are from passive microwave sensors onboard polar orbiting satellites, which measure vertically integrated water vapor (IWV), i.e., the total amount of vapor in the atmosphere from the surface to space (g/cm2).
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54 Responses to Atmospheric Rivers: key to extratropical water vapor transport

  1. pwl says:

    Minor typo, first paragraph, second sentence begins with: “Thise of us”, most likely you meant “Those of us”.

    REPLY: Thanks, fixed. I blame 4AM insomnia – Anthony

  2. John Marshall says:

    Very interesting and an important area for further research.
    Thanks Anthony.

  3. Deekaman says:

    It appears someone at NOAA is “off the reservation”. I read nothing of (alleged) AGW.

  4. Bill Illis says:

    I’ve always thought this model animation of clouds and winds over one full year was very instructive. I think you can see the atmospheric rivers but they don’t last very long or consistently appear in one place. This is a model animation partly based on actual observations (and the clouds in the equatorial region seem to be over-done) but it is quite interesting.

    https://www.ucar.edu/publications/nsf_review/animations/ccm3.512×256.mpg

  5. alan says:

    Earlier in the article:

    “These columns of vapor move with the weather, carrying an amount of water vapor roughly equivalent to the average flow of water at the mouth of the Mississippi River.”

    Later in the summary:

    “For comparison, a strong AR transports an amount of water vapor roughly equivalent to 10-20 times the average flow of liquid water at the mouth of the Mississippi River.”

    Which is it, “roughly equivalent” or “10 to 20 times”?

  6. caroza says:

    And your point is?

    Although atmospheric rivers come in many shapes and sizes, those that contain the largest amounts of water vapor and the strongest winds can create extreme rainfall and floods, often by stalling over watersheds vulnerable to flooding.

    More (AGW-caused) water vapour and heat energy in the system means the small ones get bigger, and the big ones get gigantic, which means a higher frequency of weather events which were previously extreme, which is exactly what’s happening. But your opening canard implies that global warming requires there to be some completely separate mechanism, and that’s as far as most people will read.

    This is not science.

  7. David Larsen says:

    If you live in the 10 year flood plain you get flooded every 10 years. 20/20 and so forth. We now have the media sensationalizing every natural occuring event as if it is an unheard of event. A lack of good planning on your part does not constitute an unnatural event or a once in an ion happening. The earth’s climate and surface are interacting and have for 6.5 billion or so years.

  8. Ian W says:

    One thing not mentioned was the heat transport that is occurring. A 400km wide band carrying “10-20 times the average flow of liquid water at the mouth of the Mississippi River” from the sub-tropics to the temperate and then dumping rain by releasing large amounts of latent heat into the atmosphere as the water vapor turns to liquid. It takes a large amount of energy to vaporise 20 times the Mississippi flow. Much of this latent heat release then escapes to space and is not governed by the temperature based Boltzmann radiation formulae.

    Perhaps this is where the ‘missing heat’ is hiding or rather escaping?

  9. johnmcguire says:

    Anthony, you post so many items of interest to laymen such as myself that I feel obligated to begin budgeting a regular contribution to help pay for what has up to now been taken for free. Thank you for your continueing help in understanding our world.

  10. Bob Tisdale says:

    Referring to the final illustration of the three atmospheric rivers, the following are the NINO3.4 SST anomalies (in parentheses) for the months of January 2005 (+0.58 deg C), November 2006 (+1.21 deg C), and October 2009 (1.03 deg C). In other words, all of those examples were during the months of low to medium strength El Ninos. Do these atmospheric rivers only occur during El Nino events?

  11. Jeff K says:

    Wow, great article, chock full of information. Too bad science and historical data often take a back seat to the alarmist environmental drum beat of the day-witness Northeast Australia.

  12. MartinGAtkins says:

    You have made a long submission but at first blush I don’t agree with the term “atmospheric rivers”. “Boundary lines” yes because it fits with fluid (in flow form) dynamics.

    Any moving fluid through another medium will form eddies at the outer edge of the flow. Interestingly this was noticed by Leonardo
    Da Vinci.

    I understand that you are looking at this as a Meteorologist so I won’t elaborate any further on fluid dynamics as it is not my area (what is?).

    I’ll book mark this post and enjoy your observations, as we struggle to understand how the laws of physics complicate our world.

  13. Bob Tisdale says:

    And to answer my own question (Do these atmospheric rivers only occur during El Nino events?) the answer is no. They simply change location during El Nino and La Nina events, according to Nusbaumer & Noone (2010). They write in the abstract, “It was found that there is shift in the position and strength of ARs with ENSO, with a poleward (equatorward) shift in AR locations during La Nina (El Nino), and a large East/West variation in the Western Pacific/Eastern Indian Ocean.”

    http://adsabs.harvard.edu/abs/2010AGUFM.A53B0211N

    And that makes sense because the convection/cloud cover/precipitation accompany the warm water during ENSO events.

  14. Harold Pierce Jr says:

    How could one carry out climate model calculations when there is a nonuniform and constantly changing distribution of water vapor in the atmosphere over such a large area of the earth?

  15. Bob Tisdale says:

    caroza says: “More (AGW-caused) water vapour and heat energy in the system means the small ones get bigger, and the big ones get gigantic, which means a higher frequency of weather events which were previously extreme, which is exactly what’s happening.”

    All assumptions on your part.

  16. mddwave says:

    I have sometimes seen storms in Northern Utah that instead of typical moving front weather pattern, it looks like “somebody left the pump on”. On reading this article on atmospheric rivers, it made wonder if I am seeing a smaller scale atmospheric “creek or stream” events. Utah doesn’t have rivers like the Mississippi.

  17. Just The Facts says:

    I’ve got a few graphics and animations that might help in visualizing this:

    Water Vapor

    Here is a static version of 250 hPa/mb Wind Speeds and Vectors – Approximately 10,000 meters (32,800 feet);

    and here’s an animated Jet Stream forecast – 250 hPa/mb Wind Speeds and Pressure – Approximately 10,000 meters (32,800 feet);

    http://www.stormsurfing.com/cgi/display_alt.cgi?a=glob_250

    This is 325K Isentropic Surface Potential Vorticity (PV) – Vorticity Assuming No Increase or Decrease in Entropy on a 325 Kelvin Surface – Click on the link below and then check the “Click to animate” box at the top of the new page;

    http://www.coaps.fsu.edu/~maue/extreme/gfs/current/pv325.html

    and finally THETA-E (Equivalent Potential Temperature) at 850 hPa/mb Approximately 1,500 meters (5,000 feet) Click on the link below and then check the “Click to animate” box at the top of the new page.

    http://www.coaps.fsu.edu/~maue/extreme/gfs/current/thetae800.html

    Several of these graphics/animations and a array of others can be found on WUWT’s Atmosphere Reference Page:

    http://wattsupwiththat.com/reference-pages/atmosphere/

    If you have any suggestions of other current atmospheric graphs, graphics or animations you’d like to see on WUWT’s Atmosphere Reference Page, please let us know.

  18. Dr T G Watkins says:

    Thanks Anthony and the ever informative Bob Tisdale.

  19. Oliver says:

    Nice to read that this research has been incorporated into routine forecasting – my dear old dad (Reg Newell) would have been pleased.

    (he was never a fan of the AGW science-is-settled arguments, to put it mildly)

  20. Oliver Ramsay says:

    caroza says:
    February 12, 2011 at 5:21 am

    And your point is?

    Although atmospheric rivers come in many shapes and sizes, those that contain the largest amounts of water vapor and the strongest winds can create extreme rainfall and floods, often by stalling over watersheds vulnerable to flooding.

    More (AGW-caused) water vapour and heat energy in the system means the small ones get bigger, and the big ones get gigantic, which means a higher frequency of weather events which were previously extreme, which is exactly what’s happening. But your opening canard implies that global warming requires there to be some completely separate mechanism, and that’s as far as most people will read.

    This is not science.
    ———————————————-

    You’ve gone and forgotten your own story line.
    It’s CO2! Remember? It makes the air less cold at night. More at the higher latitudes than in the tropics.
    This is why you invented Climate Change; because Global Warming didn’t do the trick.
    Or, is it that suddenly a build-up of CO2 near Hawaii heats the ocean and sends an extra big surge of water vapour to us in BC?
    Relative humidity has fallen significantly in all of Canada in recent years. There has been putative warming in the west and cooling in the east during this period.
    Perhaps, you have the CO2-based “scientific” explanation.

  21. James Allison says:

    caroza says:
    February 12, 2011 at 5:21 am
    Well I’ll assert that any increase in water vapour is removed out of the atmoshere by an equivalent increase in tropical thunderstorm activity.

  22. TomRude says:

    Cute post… but really this is a consequence of lower tropospheric circulation:

    http://ddata.over-blog.com/xxxyyy/2/32/25/79/Leroux-Global-and-Planetary-Change-1993.pdf

  23. Theo Goodwin says:

    “CalJet/PacJet led to the development of the NOAA Hydrometeorology Testbed (HMT; hmt.noaa.gov). HMT’s aim is to accelerate the development and prototyping of advanced hydrometeorological observations, models, and physical process understanding, and to foster infusion of these advances into forecasting operations of the NWS, and to support the broader user community’s needs for 21st Century precipitation information.”

    This is soooooooo promising. It is the beginning of real science. It is being done by real scientists. To the good side, they say “forecasting” rather than “predicting.” Maybe also to the good side, they say “physical process understanding” rather than “physical hypotheses.” All this is good because at this time they have no reasonably confirmed physical hypotheses and cannot predict anything. (Prediction would bring up the question of falsification, but they have nothing to falsify just yet.)

    To the bad side, they mention “models.” Of course, they work for the US government so they have no choice, I guess. If Holdren, Hansen, or Schmidt get wind of what they are doing they might be reassigned anyway.

    The concept of “rivers” in the atmosphere really blows away the existing “science” of manmade CO2 global warming. It does so because it shows that there really are a whole host of atmospheric phenomena that we are only beginning to study scientifically and that these phenomena must be understood before any reasonable scientific claims can be made about climate. Once these phenomena are described by physical hypotheses, scientists can ask about the effects, if any, of increasing CO2 on them. Of course, we already know about a lot of these phenomena such as El Nino, La Nina, PDO, and many related phenomena. The scientific study of all these phenomena is in its infancy because scientists have yet to produce reasonably well confirmed physical hypotheses that can be used to explain and predict the occurrence and behavior of a La Nina, to pick an example at random.

  24. Pamela Gray says:

    There actually has been an increased report of climate disasters. If one were to review the typical newscast from long ago, climate disasters were hardly ever mentioned. Now they are daily fare. I don’t blame AGW’ers for bringing that to our attention, because it is true. Reports of such things have dramatically increased. However, I do indeed blame such reminders (eg: caroza says: February 12, 2011 at 5:21 am) on very shallow understandings of the difference between “reports” and scientifically measured incidences that are falling outside the normal weather pattern variation record.

  25. P. van der Meer says:

    Seeing this blog got me jumping up and down with excitement. It is yet another perfect confirmation of Marcel Leroux’s theory of Mobile Polar Highs. But as yet, most are unwilling to take on his new theory. After all, that would mean a paradigm shift in meteorology/climate studies. And as this is a field of science too much in the public eye, I don’t expect to see this paradigm shift in my lifetime. His theory is clearly at odds with the AGW climate models, which we know to be faulty anyway. Anyone interested in reading more about this theory should read “Dynamic Analysis of Weather and Climate” by Marcel Leroux, Praxis Publishing.

  26. Richard Sharpe says:

    caroza says on February 12, 2011 at 5:21 am

    And your point is?

    Although atmospheric rivers come in many shapes and sizes, those that contain the largest amounts of water vapor and the strongest winds can create extreme rainfall and floods, often by stalling over watersheds vulnerable to flooding.

    More (AGW-caused) water vapour and heat energy in the system means the small ones get bigger, and the big ones get gigantic, which means a higher frequency of weather events which were previously extreme, which is exactly what’s happening. But your opening canard implies that global warming requires there to be some completely separate mechanism, and that’s as far as most people will read.

    This is not science.

    I’m glad you agree that the crap you are spewing is not science.

    Do you have any numbers for the additional moisture in the atmosphere caused by this putative AGW thing?

    Note that the heat content of the atmosphere is vastly dwarfed by that of the oceans.

  27. MartinGAtkins says:

    caroza

    More (AGW-caused) water vapour and heat energy in the system means the small ones get bigger, and the big ones get gigantic, which means a higher frequency of weather events which were previously extreme, which is exactly what’s happening.

    I can see you’ve studied at the Trenberth school of stupidity.

    What happened to the law of thermal dynamics?

    If all systems warm equally then no extra work can be done.

  28. ES says:

    Ian W @ February 12, 2011 at 6:23 am
    says:
    It takes a large amount of energy to vaporise 20 times the Mississippi flow. Much of this latent heat release then escapes to space and is not governed by the temperature based Boltzmann radiation formulae. Perhaps this is where the ‘missing heat’ is hiding or rather escaping?
    A lot of the heat often keeps traveling north, depending on the jet stream. After a pineapple express the northern States, Canadian prairies , and sometimes even as far north as the NWT see above average tempreatures.

  29. Roy Clark says:

    Just for reference, the observed 100 ppm increase in atmospheric CO2 concentration has produced an increase in ‘clear sky’ downward LWIR flux of 1.7 W.m-2. Over one day this is an increase of about 0.15 MJ.m-2 over 200 years. This tranlates into the daily evaporation of a film of water about 65 micron thick, around the width of a human hair. This is much smaller than the wind drive fluctuations in evaporation over the oceans. There can be no CO2 induced global warming or weather changes.

  30. These AR rivers are just the manifestations of the Lunar declinational tidal movements induced into the atmosphere. They will be better understood and predictable when the study of the timing of the tidal effects are connected to and included into the forecast process currently in use.

  31. R. Gates says:

    Very interesting. Just like any might normal river can be thought of as a flow of energy (and also a source of energy) I’d be curious to see some calculations on how much energy is transported in one of these rivers over some given period of time.

  32. harrywr2 says:

    Bob Tisdale says:
    February 12, 2011 at 6:44 am

    “Do these atmospheric rivers only occur during El Nino events?”

    I live in Seattle, Pineapple Express is a term used by local meteorologists. There may be a frequency distribution but we get a few per year no matter what.

    Parts of the Olympic Peninsula are considered rain forest averaging 200 inches of rain per year.

  33. RockyRoad says:

    Just The Facts says:
    February 12, 2011 at 7:45 am

    I’ve got a few graphics and animations that might help in visualizing this:

    Thank you for taking the time to put that insightful collection of graphics and animations together.

    After viewing them, I came to the stark realization that the vast majority of water vapor hangs around the earth’s equator, and that precious little is found in the polar regions–indeed, so little water vapor is found beyond 45 north and 45 south that both Greenland and Antarctica are polar deserts.

    So my question is this–what process or mechanism during an Ice Age pushes sufficient moisture from the equatorial areas of the earth to polar and sub-polar regions to build ice sheets? I don’t think simply cooling the earth would do it–accumulating 2 miles of ice would be difficult in a polar desert environment, especially since a significantly cooler earth reduces oceanic evaporation. Seems like such a process or mechanism during an Ice Age would have to enlarge the circum-equitorial band of water vapor and move at least parts of it pole-ward.

  34. If during Ice ages the magnetic pole of the fields of the sun were oriented on the same axis as the poles of rotation instead of off ~12 degrees. Then the flopping around of the polarity of the solar wind would stay balanced and neutral, taking the polarity shifts on the 27.32 period of solar rotation out of the current conditions, thus allowing the North/South declination of the moon relative to the ecliptic to decrees from the current +/- 5 degrees to much less.

    Currently when the lunar declinational excursions cross the 23.5 degree point in the 18.6 year Mn cycle of change in declination to compensate for the ~12 degree tilt of the solar magnetic poles, we get the type of massive meridional flow surges and blocking highs that drive maximal volume surges in these AR production patterns.

    As evidenced by the past summers Russian heat waves, and Pakistan floods also the large area of heavy precipitation off of the East coast of the USA this past summer, that were driven into the Coastal areas of Western Greenland, creating and maintaining the surge of warm surface water that were the byproduct of the late hurricane season in the N Atlantic in 2010, slowing down the “Arctic Ice recovery”.

    In Ice ages IF these same effects were to be enhanced by the Lunar declination staying on the ecliptic plane for very long times instead of the “normal current 3 year transition times” this mechanism for the continual pumping of massive amounts of warm moisture laden tropical air masses could then easily transport the volumes of moisture needed to generate the massive snow and ice accumulation needed to maintain continental sized and miles thick ice sheets, seen commonly in the areas snow covered at this time.

  35. Roger Knights says:

    We already have the term “jet streams,” so “atmospheric rivers” fits in.

  36. Just The Facts says:

    RockyRoad says: February 12, 2011 at 11:28 am

    “So my question is this–what process or mechanism during an Ice Age pushes sufficient moisture from the equatorial areas of the earth to polar and sub-polar regions to build ice sheets?”

    I’d hypothesize that the Hadley Cells, Ferrell Cells and Polar Cells would continue to operate during an Ice Age, though the Hadley Cells and Ferrell Cells would probably be shorter and Polar Cell longer.

    “There are three wind cells or circulation belts between the equator and each pole: the trade winds (Hadley cells), prevailing westerlies (Ferrell cells), and polar easterlies (polar Hadley cells). The trade winds or Hadley cells are named after the English scientist George Hadley (1685–1768), who first described them in 1753. As air is heated at the equator, it rises in the troposphere, the lowest 10 miles (16 kilometers) of Earth’s atmosphere. In the wake of the warm rising air, low pressure develops at the equator. When the air reaches the top of the troposphere, called the tropopause, it can rise no farther and begins to move toward the poles, cooling in the process.

    At about 30 degrees latitude north and south, the cooled air descends back to the surface, pushing the air below it toward the equator, since air flows always move toward areas of low pressure. When the north and south trade winds meet at the equator and rise again, an area of calm develops because of the lack of cross-surface winds. Early mariners called this area the doldrums (from an Old English word meaning dull) because they feared their sailing ships would be stranded by the lack of wind.

    While most of the trade-wind air that sinks at 30 degrees latitude returns to the equator, some of it flows poleward. At about 60 degrees latitude north and south, this air mass meets much colder polar air (the areas where this occurs are known as polar fronts). The warmer air is forced upward by the colder air to the tropopause, where most of it moves back toward the equator, sinking at about 30 degrees latitude to continue the cycle again. These second circulation belts over the middle latitudes between 30 degrees and 60 degrees are the prevailing westerlies or Ferrell cells, named after the American meteorologist William Ferrell (1817–1891), who discovered them in 1856.”

    http://www.scienceclarified.com/As-Bi/Atmospheric-Circulation.html

    Here’s a good visual of Earth’s Atmospheric Circulation;

    I would also hypothesize that the Jet Streams would still move poleward in the hemispheric summer during an ice age, though not as far as they currently do.

    “In 1944, an especially dramatic type of atmospheric air movement was discovered: the jet streams. These permanent air currents are located at altitudes of 30,000 to 45,000 feet (11 to 13 kilometers) and generally move with speeds ranging from about 35 to 75 miles (55 to 120 kilometers) per hour. It is not uncommon, however, for the speed of jet streams to be as high as 200 miles (320 kilometers) per hour.

    These narrow tubes of air, which usually travel west to east, are created by the great temperature and pressure differences between air masses. There are four major jet streams, two in each hemisphere. Polar jet streams, formed along the polar front between the Ferrell and polar Hadley cells, move between 30 degrees and 70 degrees latitude. The other jet streams move between 20 degrees and 50 degrees latitude.

    Jet streams do not move in straight lines, but in a wavelike manner. They may break apart into two separate streams and then rejoin, or not. In winter, because of greater temperature differences, jet streams are stronger and move toward the equator. In summer, with more uniform temperatures, they weaken and move poleward. The movement of the jet streams is an important factor in determining weather conditions in mid-latitude regions since they can strengthen and move low-pressure systems.”

    http://www.scienceclarified.com/As-Bi/Atmospheric-Circulation.html

    Here’s further background on Earth’s Atmospheric Circulation:

    http://en.wikipedia.org/wiki/Atmospheric_circulation

    Finally, I’d hypothesize that Polar Vortices would be an important factor:

    http://en.wikipedia.org/wiki/Polar_vortex

    Polar Vortices “are caused when an area of low pressure sits at the rotation pole of a planet. This causes air to spiral down from higher in the atmosphere, like water going down a drain.”

    http://www.universetoday.com/973/what-venus-and-saturn-have-in-common/

    Here’s an animation of the Arctic Polar Vortex in Winter 2008 – 09;

    here’s an animation of the currently uncoalesced Arctic Polar Vortex and;

    http://www.cpc.ncep.noaa.gov/products/intraseasonal/z500_nh_anim.shtml

    here’s an animation of the currently uncoalesced Antarctic Polar Vortex:

    http://www.cpc.ncep.noaa.gov/products/intraseasonal/z500_sh_anim.shtml

    I would hypothesize that a persistent coalesced Arctic Polar Vortex would form during an ice age, breaking down occasionally during summer, and thus allowing warm moist air poleward.

    Not sure how much this helped. I am still trying to figure out how Earth’s atmosphere operates today, much less accurately predict what it might do during an ice age… :)

  37. So the shift in paradigm I am proposing is only adding the lunar declinational tidal effects to the modulation of the original Hadley cell jet stream average locations and zonal components, as currently understood. So that the other modulating forces can also be added to the point where the cyclic patterns can be added to what is known and used in conventional forecasting.

  38. Charles Nelson says:

    I was once amazed by what appeared to be such a system crossing from the Pacific ocean, over the Gulf of Mexico on its way towards Europe.
    Right now(this summer) they can reguarly be seen crossing Australia from NW to SE bringing rain and cloud from the tropics to the formerly dry cities of Adelaide and Melbourne where the Warmists are currently gnashing their teeth as their doom laden predictions of never ending drought are flushed away like so much soggy toilet tissue!
    The very thought of Tim ‘Ghost Metropolis’ Flannery, (a lead AGW scaremonger who said that by now Brisbane, yes BRISBANE would become a ghost metropolis due to water shortages) torturously trying to twist the AGW story to fit with reality fills me with delight!

  39. Mike Borgelt says:

    Charles Nelson :
    February 12, 2011 at 1:31 pm
    Yes Charles, the transport of water from the tropical oceans NW of Australia causing rain in Melbourne and other parts of SE Australia is well known.
    They showed us a nice little movie about the setting up of the Giles weather station during the first few days at BoM meteorologist course in 1971 with one reason for it being early warning that this was about to happen(this was before satellites etc). Probably had more to do with British nuclear weapons tests and Woomera rocket range though. Nice disinformation project.

  40. Paul Vaughan says:

    Leroux wrote about these patterns before the term “atmospheric river” (“AR”) took root:

    Leroux, Marcel (1993). The Mobile Polar High: a new concept explaining present mechanisms of meridional air-mass and energy exchanges and global propagation of palaeoclimatic changes. Global and Planetary Change 7, 69-93.

    http://ddata.over-blog.com/xxxyyy/2/32/25/79/Leroux-Global-and-Planetary-Change-1993.pdf


    Richard Holle, it’s not just lunar declination; that’s just one of the factors (affecting mass distribution, circulation, & insolation patterns).

  41. MaxL says:

    It is fascinating to be able to look at how the atmosphere actually flows. Watching all the streams and eddies is almost hypnotizing. A while back we did a paper on atmospheric flows. It includes several animations of case studies of the flow of air particles. It is done backward in time, which means the flow starts out at its end point and then moves back in time toward its origin. You can access the paper on-line at

    http://www.nwas.org/ej/2007/2007.php

    Then go to the paper titled “On Calculating Source Regions Using a
    Non-Diffusive Lagrangian Trajectory Model”. Here is the link:

    http://www.nwas.org/ej/2007-EJ2/

    There are 3 animations near the end of the paper. Just “Click for animation” were it tells you to.

    Enjoy.

  42. Ian Cooper says:

    New Zealand is often at the downstream end of AR’s that flow NW to SE from Australia across the Tasman Sea. A weak example can be seen at this web site,

    Some AR’s can seem to be almost locked into place by a blocking high to the north. Although the general movement of the moisture front across New Zealand is usually from SW to NE, radar images show that the moisture coming in from the sub-tropics/tropics is at right angles to the fronts directional flow. If you are underneath such a system and on the western side of N.Z. then it seems like a conveyor belt is unloading on you. Hence why I often refer to it as the Nor’ West Conveyor.

    Fjordland, at the bottom west corner of New Zealand, juts out into the Tasman Sea and cops the brunt of the Nor’ West Conveyor. Most locations measure their annual rainfall in mm’s. Fjordland in particular, and the West Coast of the South Island in general, measure theirs in metres! Temperate rain forests are the norm in an area once dominated by glaciers. The Tararua Ranges at the bottom of the North Island, and the volcanoe, Mt Egmont/Taranaki are the only North Island locations that have similar rainfall quantities.

    The Nor’ West Conveyor is probably the main reason that the two major western glaciers descending from the Southern Alps, Franz Josef & Fox, are advancing, whilst their eastern cousins are largely doing a starve on the otherside of the divide.

  43. dp says:

    It might be less unsettling for those who equate a newer term with a newer phenomenon to link the AR idea to jet streams which are well known. Perhaps a quick tour of well known variations of the jet streams in el niño, la niña years would help, too. The MSM is full of AR stories like it was something new (meaning man-made) and to be feared (OMG! Bigger threat than earthquakes!).

  44. LazyTeenager says:

    That’s very impressive.

    So the next question is; was there an atmospheric river associated with the recent USA snow falls or was that a different phenomena?

  45. Geoff Sherrington says:

    To the south of the Equator, what is the dominant direction of these rivers?

    I ask because Tropical Cyclone Yasi of a week ago came on a straight path from about 170E 15S, to impact the Queensland coast tracking about 250-260 degrees. See
    http://www7320.nrlssc.navy.mil/global_nlom32/navo/WHOSP1_nlomw12930doper.gif Look at 20110201 or so, though it was detected near Fiji about 27 Jan. 20110127.

    I’m not even certain if this event fits the description, but I can’t work out why Yasi took this direction. Its eye’s movement averaged about 30-40 km per hour when it was over the sea.

  46. Rich says:

    It amazes me that so many people reading this web page have never heard of this before. I remember reading about this phenomenon more than 30 years ago. The article explained how massive quantities of water, equivalent to the water flowing in the Amazon river, was flowing in the atmosphere in a pattern similar to that of the jet streams.

    If the AGW’ers don’t know of this they should seek a new profession and if they are ignoring it they are doing so on purpose.

  47. Paul Jackson says:

    Wow 5 grams of water vapor per square cm of surface is a lot of water in the air, that’s 0.27 mols, lets say 45 kJ /mol at tropical temperatures for the Enthalpy of vaporization, gives 12.5 kJ/cm^2, or 52.25 Kcal/cm^2, to evaporate the water; now spreading that over an area 400 Km wide by 1200 Km long is 4.8*10^15 cm^2 or 6*10^19J!
    6*10^19J is the same as 14,340 Megatons! That’s some serious heat disapation, as they say, “numbers too big to fit in Human imagination”. Where did the excess ocean heat go, I’d say up in the air was a good place to start looking.

  48. rbateman says:

    caroza says:
    February 12, 2011 at 5:21 am

    Far greater AR storms have hit California in the historic past. The Indians here warned about them. The storms in the 1860’s and 1880’s have never been equalled since. Last year’s El Nino, strong as it was, did not flood out the Sacramento Valley and create an inland sea, such as happened before we got here. 1982-83 resulted, not in a big flood, but a whopping snowpack that took 2 years to melt down. No AGW there.

  49. P. van der Meer says:

    RockyRoad says:
    February 12, 2011 at 11:28 am

    “So my question is this–what process or mechanism during an Ice Age pushes sufficient moisture from the equatorial areas of the earth to polar and sub-polar regions to build ice sheets? “

    According to Leroux’s theory of Mobile Polar Highs (MPH), as the planet gets colder in an ice age these MPHs descending from the polar areas towards the equator become more vigorous and thereby also generate more powerful depressions carrying even more moisture towards the polar areas to be dropped as snow to become ice. The same theory also neatly explains why there weren’t any ice sheets over eastern Siberia.

  50. P. van der Meer says:

    LazyTeenager says:
    February 12, 2011 at 6:43 pm

    “So the next question is; was there an atmospheric river associated with the recent USA snow falls or was that a different phenomena? “

    Yes, it was. According to Leroux’s theory this “river” gets generated by a Mobile Polar High (MPH) originating from the Canadian Arctic and travelling south. This “river” carries the excess moisture up from the Gulf of Mexico and is then forced to rise over the cold air of a next MPH thereby dropping it’s moisture in the form of snow into the cold air below. It would also explain why this winter Hudson Bay was slow to freeze over, because of all that relatively nice warm air arriving there from the Gulf. And it also explains why Mexico is suffering intense cold – more vigorous MPHs!

  51. Jay Banks says:

    Interesting information! It can definitely bring some new insight in atmospheric changes. I wonder what else can cause it and how it is going to be explaining afterwards… I understand that scientists need more advanced technology to examine this phenomenon. Hopefully you´ll get this kind of support soon.

  52. Feet2theFire says:

    I don’t know if it is exactly the same thing, but several times a year there is something that looks like these rivers that lines up from the area of central-to-east Texas toward IL-WI, more or less. It is a major conveyor of warmth and moisture to the U.S. midwest. Sometimes it is blocked making it more or less stationary, and sometimes not.

    It was definitely the cause of the flooding in the Chicago area in September 1986. I am virtually certain it was behind the huge flooding in the upper Mississippi River in 1993 and 2003, when a blocking high prevented it from moving off to the east. In addition, this was the patten in biggest tornado day in history in 1974, with tornadoes across states from Texas to Ohio, including the Xenia, Ohio super tornado. I’ve always understood it to be connected with the frequent tornadoes in northern Texas, eastern Oklahoma and Kansas, especially if it is shifted a bit to the west. It seems to be the collision of the warm moist low-pressure Gulf air masses with the cool continental highs coming in from the west and northwest.

    The colder air mass pushes under and lifting the warm, moist air mass up to elevations where the dew point meets the warm moisture, creating the conditions of clouds and rain, all sliding NNE in what I’ve referred to as a “train of rain”. (It may be simplistic thinking, but I personally think the southern front edge of the lifting air bulge – the “atmospheric topography” – of this collision literally rolls/spins the boundary air, with the rolling creating the angled funnels of tornadoes. This is somewhat different, perhaps from what forms tornadoes within hurricanes.)

    Like hurricanes follow a bit of a U-turn path from the east and then turn a bit north and then northeast after making landfall along the Gulf coast, the easterly Gulf air’s boundary makes it to about about San Antonio (where serious flash floods can occur from this) before turning north and then NE.

    The rotation of the two systems funnels the air along the SSW-NNE boundary, and it has quite a bit of stability in its straight-line shape, with a heading of about 30° east of north.

    I’ve seen this hundreds of times on weather maps. I am surprised this wasn’t included in the article. Perhaps because they were focusing on oceanic systems.

  53. _Jim says:

    Feet2theFire February 14, 2011 at 1:14 am

    I don’t know if it is exactly the same thing, but several times a year there is something that looks like these rivers that lines up from the area of central-to-east Texas toward IL-WI, more or less. It is a major conveyor of warmth and moisture to the U.S. midwest. …

    I’m thinking: not so much; After having lived down here in Texas for nigh onto 30 years, it’s easier to see (and feel!), via surface (data) plots and real-time observation of storm formation and movement that most of the moisture transported is at low-levels northward (and eastward) from the GOM (the gulf; esp during spring and summer months) … basically east of I-35 as the meteorologists and the hydrologists can point out via historical rainfall charts of these areas (up into as far north as Kansas as I recall from the rainfall charts).

    That’s not to discount an event or two involving AR in any period of years and the occasional hurricane which draws with it an enormous airmass …

    .

  54. upcountrywater says:

    I’m liking the 13 Oct. 2009.
    Can be hot, very hot there in the Philippines, Equator hot.
    A massive 6,000 mile river, gushing for weeks….and weeks…

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