From NCAR/UCAR:
BOULDER, Colo. — The crippling wintertime droughts that struck California from 2013 to 2015, as well as this year’s unusually wet California winter, appear to be associated with the same phenomenon: a distinctive wave pattern that emerges in the upper atmosphere and circles the globe.
CREDIT Image by Haiyan Teng and Grant Branstator.
Scientists at the National Center for Atmospheric Research (NCAR) found in a recent study that the persistent high-pressure ridge off the west coast of North America that blocked storms from coming onshore during the winters of 2013-14 and 2014-15 was associated with the wave pattern, which they call wavenumber-5. Follow-up work showed that wavenumber-5 emerged again this winter but with its high- and low-pressure features in a different position, allowing drenching storms from the Pacific to make landfall.
“This wave pattern is a global dynamic system that sometimes makes droughts or floods in California more likely to occur,” said NCAR scientist Haiyan Teng, lead author of the California paper. “As we learn more, this may eventually open a new window to long-term predictability.”
The finding is part of an emerging body of research into the wave pattern that holds the promise of better understanding seasonal weather patterns in California and elsewhere. Another new paper, led by NCAR scientist Grant Branstator, examines the powerful wave pattern in more depth, analyzing the physical processes that help lead to its formation as well as its seasonal variations and how it varies in strength and location.
The California study was published in the Journal of Climate while the comprehensive study into the wave patterns is appearing in the Journal of the Atmospheric Sciences. Both papers were funded by the National Science Foundation, which is NCAR’s sponsor, as well as by the Department of Energy, the National Oceanic and Atmospheric Administration, and NASA.
The new papers follow a 2013 study by Teng and Branstator showing that a pattern related to wavenumber-5 tended to emerge about 15-20 days before major summertime heat waves in the United States.
Strong impacts on local weather systems
Wavenumber-5 consists of five pairs of alternating high- and low-pressure features that encircle the globe about six miles (10 kilometers) above the ground. It is a type of atmospheric phenomenon known as a Rossby wave, a very large-scale planetary wave that can have strong impacts on local weather systems by moving heat and moisture between the tropics and higher latitudes as well as between oceanic and inland areas and by influencing where storms occur.
The slow-moving Rossby waves at times become almost stationary. When they do, the result can be persistent weather patterns that often lead to droughts, floods, and heat waves. Wavenumber-5 often has this stationary quality when it emerges during the northern winter, and, as a result, is associated with a greater likelihood of persistent extreme events.
To determine the degree to which the wave pattern influenced the California drought, Teng and Branstator used three specialized computer models, as well as California rainfall records and 20th century data about global atmospheric circulation patterns. The different windows into the atmosphere and precipitation patterns revealed that the formation of a ridge by the California coast is associated with the emergence of the distinctive wavenumber-5 pattern, which guides rain-producing low-pressure systems so that they travel well north of California.
Over the past winter, as California was lashed by a series of intense storms, wavenumber-5 was also present, the scientists said. But the pattern had shifted over North America, replacing the high-pressure ridge off the coast with a low-pressure trough. The result was that the storms that were forced north during the drought winters were, instead, allowed to make landfall.
Clues to seasonal weather patterns
Forecasters who predict seasonal weather patterns have largely looked to shifting sea surface temperatures in the tropical Pacific, especially changes associated with El Niño and La Niña. But during the dry winters of 2013-14 and 2014-15, those conditions varied markedly: one featured the beginning of an El Niño while the sea surface temperatures during the other were not characteristic of either El Niño or La Niña.
The new research indicates that the wave pattern may provide an additional source of predictability that sometimes may be more important than the impacts of sea surface temperature changes. First, however, scientists need to better understand why and when the wave pattern emerges.
In the paper published in Journal of the Atmospheric Sciences, Branstator and Teng explored the physics of the wave pattern. Using a simplified computer model of the climate system to identify the essential physical processes, the pair found that wavenumber-5 forms when strong jet streams act as wave guides, tightening the otherwise meandering Rossby wave into the signature configuration of five highs and five lows.
“The jets act to focus the energy,” Branstator said. “When the jets are present, the energy is trapped and cannot escape.” But even when the jets are present, the wavenumber-5 pattern does not always form, indicating that other forces requiring study are also at play.
The scientists also searched specifically for what might have caused the wave pattern linked to the severe California drought to form. In the paper published in the Journal of Climate, the pair found that extremely heavy rainfall from December to February in certain regions of the tropical Pacific could double the probability that the extreme ridge associated with wavenumber-5 will form. The reason may have to do with the tropical rain heating parts of the upper atmosphere in such a way that favors the formation of the wavenumber-5 pattern.
But the scientists cautioned that many questions remain.
“We need to search globally for factors that cause this wavenumber-5 behavior,” Teng said, “Our studies are just the beginning of that search.”
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But the scientists cautioned that many questions remain.
“We need to search globally for factors that cause this wavenumber-5 behavior,” Teng said, “Our studies are just the beginning of that search.”
the beginning of a long journey.
The ridiculously resilient ridge vs the terribly tenacious trough. There was this forecaster at KCRA in Sacramento in the 70’s, Harry Geise, who thought he had Rossby waves in the “upper atmosphere” dialed in. Wave 5 and the numbering sequence in the illustrations is not clear to me. Often there are only four Rossby waves. Here is the 250 mb map today over mean surface pressure.
I guess I can see five waves there. Even the map projection makes a difference.
I don’t see the waves but in the first picture I do see a mermaid swimming with a manatee. Oh, and she’s topless!
Yes it’s all giving me ideas for creative Easter egg decorating.
I can see Elvis!
Rorschach?
I got the spelling right the third time.
Like Ray in SC, I am at all sure there are five waves in the first map.
A polar bear and a kangaroo, with big ears, attacking Easter Eggs? well, maybe . . . . .
And the second is something from ‘Phantom of the Opera’.
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Like Ray in SC, I am (dammit) NOT at all sure there are five waves in the first map.
Sorry.
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I do believe that Michael Mann’s upcoming paper on extreme events caused by CAGW brings in the Jet Stream. Perhaps we have convergence here? How wonderful!
Well, he would try that wouldn’t he.
To be persuasive he needs to say how CAGW changes the gradient of tropopause height between equator and poles in the manner observed.
Previously, CAGW was proposed only to shift the jets and climate zones poleward (more zonality) so I’d be interested to see how he proposes to deal with the more recent shift towards meridionality (since 2000 or thereabouts).
He also needs to explain the shifts of the climate zones that occurred from MWP to LIA when CAGW could not have been a factor.
Stephen
What is the tropopause trend you indicated. Increasing in height at the equator ? Seasonal variation. ?
Tropopause height between equator and poles should be envisaged as a pair of see-saws set end to end with one running longitudinally across each hemisphere and an independently moving joint or fulcrum near the equator.
Seasonal changes simply move the joint at the equator northward and southward each year. Lengthening one see-saw and shortening the other.
For longer term climate change the sun moves the troposphere height up or down above the poles and the ocean oscillations move troposphere height up or down above warming or cooling ocean surfaces (mostly near the equator).
The net interplay between the solar top down and oceanic bottom up influences on tropopause height causes the average gradient of tropopause height between equator and poles to be in constant flux.
That gradient determines how much physical space the tropospheric weather systems have in the vertical plane in which to operate between the equator and poles.
If the height above the poles drops relative to the height above the equator then the climate zones are pushed equatorward into a more meridional pattern.
If the height above the poles rises relative to the height above the equator then the climate zones are pushed poleward into a more zonal pattern.
Zonal results in less clouds and global warming whereas meridional results in more clouds and global cooling.
For a diagnostic indicator of global warming or cooling we need to be able to ascertain the degree of jet stream meridionality / zonality and / or the total global cloudiness.
Currently, the ongoing temperature pause implies that the height above the poles relative to that above the equator is setting a level of global cloudiness that results in neither warming nor cooling. That must change in due course.
“He also needs to explain the shifts of the climate zones that occurred from MWP to LIA when CAGW could not have been a factor.”
It has to do with tree rings and chicken entrails Stephen. Real science stuff. You wouldn’t understand. (Besides which, IIRC Mann doesn’t believe in either the MWP or the LIA.)
Thanks. This would then alter or influence the rosby waves ?
That’s a good description Stephen. The CO2 hypothesis has no explanation for the multidecadal expansion of the Hadley cells. And geopotential heights have been shown to depend on solar activity.
http://i.imgur.com/uVotN0L.png
From Labitzke, K. (2001). The global signal of the 11-year sunspot cycle in the stratosphere: Differences between solar maxima and minima. Meteorologische Zeitschrift, 10(2), 83-90.
http://strat-www.met.fu-berlin.de/labitzke/solar_signal/MetZ_Labitzke_2001.pdf
Thanks Javier.
In due course I think it will be more fully appreciated as an accurate, basic description of the underlying mechanism for natural climate variability.
Maybe someone could put me in charge of a research project with a large budget ? 🙂
And this is news??!! Rossby waves have been known about for how bloody long???
As far a prediction goes, it’s non-linear chaotic system.
We can say where it is now. We know (or can re-construct) where it has been in the past (via weather records).
But in a non-linear complex system, that says nothing about where it will be in say 2 years with any confidence.
Piers Corbyn has a good YouTube on Global waves https://youtu.be/6R26PXRrgds?list=PL4Fgfe69FySJVHK2SMLtp2NXgXBkIbhck
Precipitation in the Santa Barbara Basin has been attributed a solar control:
Nederbragt, A. J., & Thurow, J. (2005). Geographic coherence of millennial-scale climate cycles during the Holocene. Palaeogeography, Palaeoclimatology, Palaeoecology, 221(3), 313-324.
http://www.sciencedirect.com/science/article/pii/S0031018205001045
If true, the atmospheric pattern might be related to the current solar centennial minimum (SC24-25) and there could be more unusual rain patterns during the next winters for California.
“It never rains in Southern California”, unless solar activity is low.
The discussion here is good from a climate/science standpoint. I think, however, this was all summed up by Steinbeck in one of his books, the comment-During the wet years in California the settlers moved out of the valleys and moved into the hills, during the dry years these farms failed and people moved back to the valleys- I think the comment was in East of Eden, but it may have been in another one of his books. Pretty well summed up the drought/wet weather of California and it stuck with me.
Speaking of standing waves – I published a paper about n = 4 standing waves in the Southern Hemisphere mid-latitudes that were driven by upper atmospheric lunar tides.
Wilson, I.R.G. and Sidorenkov, N.S., Long-Term Lunar Atmospheric Tides in the
Southern Hemisphere, The Open Atmospheric Science Journal,
2013, 7, 51-76
http://benthamopen.com/contents/pdf/TOASCJ/TOASCJ-7-51.pdf
Abstract: The longitudinal shift-and-add method is used to show that there are N=4 standing wave-like patterns in the summer (DJF) mean sea level pressure (MSLP) and sea-surface temperature (SST) anomaly maps of the Southern Hemisphere between 1947 and 1994. The patterns in the MSLP anomaly maps circumnavigate the Earth in 36, 18, and 9 years. This indicates that they are associated with the long-term lunar atmospheric tides that are either being driven by the 18.0 year Saros cycle or the 18.6 year lunar Draconic cycle. In contrast, the N=4 standing wave-like patterns in the SST anomaly maps circumnavigate the Earth once every 36, 18 and 9 years between 1947 and 1970 but then start
circumnavigating the Earth once every 20.6 or 10.3 years between 1971 and 1994. The latter circumnavigation times indicate that they are being driven by the lunar Perigee-Syzygy tidal cycle. It is proposed that the different drift rates for the patterns seen in the MSLP and SST anomaly maps between 1971 and 1994 are the result of a reinforcement of the lunar Draconic cycle by the lunar Perigee-Syzygy cycle at the time of Perihelion. It is claimed that this reinforcement is part of a 31/62/93/186 year lunar tidal cycle that produces variations on time scales of 9.3 and 93 years. Finally, an N=4 standing wave-like pattern in the MSLP that circumnavigates the Southern Hemisphere every 18.6 years will naturally
produce large extended regions of abnormal atmospheric pressure passing over the semi-permanent South Pacific subtropical high roughly once every ~ 4.5 years. These moving regions of higher/lower than normal atmospheric pressure will increase/decrease the MSLP of this semi-permanent high pressure system, temporarily increasing/reducing the strength of the East-Pacific trade winds. This may led to conditions that preferentially favor the onset of La Nina/El Nino events.
It would appear that the many “laymen” posting above sincerely believe “the jet stream” to be an entity which is able to exist alone and solely by itself, without support from other determining factors such as associated Rossby constructs (waves) and associated low pressure systems.
I do hope this is NOT actually the case.
High and low pressure systems are an artefact of the Global Electric Circuit.
“Point 1 Together, the earth’s surface and the ionosophere resemble a charged spherical capacitor, i.e. two oppositely charged conducting electrodes with an insulator in between. The ground is normally negatively charged during fair weather. Positive charge is found in the air between the ground and the ionosphere (the charge would normally be found on the second electrode in a typical capacitor). The positive charge is attached to small particles in the air (aerosols) and is relatively immobile (compared to air molecules due to the large size and large inertia of the particles). These are called “large ions.” Most of the positive charge is found near the ground. ”
http://www.atmo.arizona.edu/students/courselinks/spring15/atmo589/ATMO489_online/lecture_1/lect1_global_elec_circuit.html
“Scientists link California droughts and floods to distinctive atmospheric waves”
Seriously, they link weather events to the atmosphere? WHOA!!! Where can I find a paid job like that?
If I get around to reading the actual papers, I will look for data about where and how much wet there was when CA was dry, and where and how little wet there was when CA was wet.
My takeaway from this is that they found a 5 node Rossby wave pattern tends to be stationary. When the pattern is stationary, the weather in the hemisphere remains stable with some areas getting lots of rain and others getting drought. A shift in the phase, changes which areas are wet and and which are dry.
It is almost a tautology, one would would predict a stationary Rossby wave during unusually protracted wet or dry patterns. The recognition of a five node pattern seems to be new. It might be used to predict extended periods of rain or drought when it appears. They need to be bold and make predictions to test the hypothesis. Using the limited historical data is just curve fitting.
See what sending out them negative waves did, Moriarty?