Planetary Wave Resonance And Increasing Weather Extremes

[bluewave]

 

http://www.nature.com/articles/srep45242

Persistent episodes of extreme weather in the Northern Hemisphere summer have been shown to be associated with the presence of high-amplitude quasi-stationary atmospheric Rossby waves within a particular wavelength range (zonal wavenumber 6–8). The underlying mechanistic relationship involves the phenomenon of quasi-resonant amplification (QRA) of synoptic-scale waves with that wavenumber range becoming trapped within an effective mid-latitude atmospheric waveguide. Recent work suggests an increase in recent decades in the occurrence of QRA-favorable conditions and associated extreme weather, possibly linked to amplified Arctic warming and thus a climate change influence. Here, we isolate a specific fingerprint in the zonal mean surface temperature profile that is associated with QRA-favorable conditions. State-of-the-art (“CMIP5”) historical climate model simulations subject to anthropogenic forcing display an increase in the projection of this fingerprint that is mirrored in multiple observational surface temperature datasets. Both the models and observations suggest this signal has only recently emerged from the background noise of natural variability.

http://www.pnas.org/content/113/25/6862.

Weather extremes are becoming more frequent and severe in many regions of the world. The physical mechanisms have not been fully identified yet, but there is growing evidence that there are connections to planetary wave dynamics. Our study shows that, in boreal spring-to-autumn 2012 and 2013, a majority of the weather extremes in the Northern Hemisphere midlatitudes were accompanied by highly magnified planetary waves with zonal wave numbers m = 6, 7, and 8. A substantial part of those waves was probably forced by subseasonal variability in the extratropical midtroposphere circulation via the mechanism of quasiresonant amplification (QRA). The results presented here support the overall hypothesis that QRA is an important mechanism driving many of the recent exceptional extreme weather events.

http://iopscience.iop.org/article/10.1088/1748-9326/10/1/014005/meta

New metrics and evidence are presented that support a linkage between rapid Arctic warming, relative to Northern hemisphere mid-latitudes, and more frequent high-amplitude (wavy) jet-stream configurations that favor persistent weather patterns. We find robust relationships among seasonal and regional patterns of weaker poleward thickness gradients, weaker zonal upper-level winds, and a more meridional flow direction. These results suggest that as the Arctic continues to warm faster than elsewhere in response to rising greenhouse-gas concentrations, the frequency of extreme weather events caused by persistent jet-stream patterns will increase.

http://cpo.noaa.gov/News/News-Article/ArtMID/6226/ArticleID/1498/Scientists-link-California-droughts-and-floods-to-distinctive-atmospheric-waves

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. 

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.

 

 

 

 

[blizzard1024]

So in a colder climate, the storms  and extremes are weaker. All this flies in the face of baroclinic instability. That used to be the primary way that  extratropical waves develop because of a temperature difference between the poles and the equator. With the Arctic warming faster, baroclinicity weakens and so do storms. That is what I learned. But I guess climatologists have figured something out new. A warmer Arctic means more storminess and extremes, which plays right into the hands of the global warming scare mongers.  Nice politically correct paper.... 

[Sophisticated Skeptic]

lol, I love how they try to use equations and smart talk...as if they completely know everything that's going on.

there are way too many variables in play to put a finger on exactly what's causing the sudden "stagnant" ness .      Increased water vapor in the atmosphere will slow weather patterns across the globe.   All the additional seeding we've been doing isn't helping.   We need to reduce H2O , not JUST CO2.  

Government recognition that we've been seeding storms for over 20 years now -

 

 

[WidreMann]

4 hours ago, blizzard1024 said:

So in a colder climate, the storms  and extremes are weaker. All this flies in the face of baroclinic instability. That used to be the primary way that  extratropical waves develop because of a temperature difference between the poles and the equator. With the Arctic warming faster, baroclinicity weakens and so do storms. That is what I learned. But I guess climatologists have figured something out new. A warmer Arctic means more storminess and extremes, which plays right into the hands of the global warming scare mongers.  Nice politically correct paper.... 

I don't think that's what they said at all. They are talking about weather patterns becoming stuck, as it were, which leads to what people tend to think of as extreme weather: long-lasting droughts and heat ridges, or extended periods of stormy or wet weather. That seems to fit with my own anecdotal observations. The weather does seem a lot less variable in the short-medium range and patterns do seem to get stuck more than they used to.

But they aren't talking about the strength of individual storms. I would doubt whether that would be super-relevant at this point because while the Arctic has warmed significantly, it still remains significantly colder than the midlatitudes (which have also warmed, but not as much), so baroclinicity remains a significant factor and probably will forever, regardless of climate change.

I feel like you are attacking a strawman.

[WidreMann]

4 hours ago, Sophisticated Skeptic said:

lol, I love how they try to use equations and smart talk...as if they completely know everything that's going on.

there are way too many variables in play to put a finger on exactly what's causing the sudden "stagnant" ness .      Increased water vapor in the atmosphere will slow weather patterns across the globe.   All the additional seeding we've been doing isn't helping.   We need to reduce H2O , not JUST CO2.  

Government recognition that we've been seeding storms for over 20 years now -

 

 

Yeah, the old "it's too complicated to understand, so there's definitely absolute nothing going on" excuse. What if it's actually even worse than we thought because of our limited knowledge? Why do the skeptics never bring up that concern?

[bluewave]

https://www.pik-potsdam.de/news/press-releases/winter-cold-extremes-linked-to-high-altitude-polar-vortex-weakening

Some regions like Western Siberia even show a downward temperature trend in winter. In stark contrast, the Arctic has been warming rapidly. Paradoxically, both phenomena are likely linked: When sea-ice North of Scandinavia and Russia melts, the uncovered ocean releases more warmth into the atmosphere and this can impact the atmosphere up to about 30 kilometers height in the stratosphere disturbing the polar vortex. Weak states of the high-altitude wind circling the Arctic then favors the occurrence of cold spells in the mid-latitudes. Previous work by Kretschmer and colleagues identified this causal pathway in observational data and it is further supported by several climate computer simulation studies.

“Our latest findings not only confirm the link between a weak polar vortex and severe winter weather, but also calculated how much of the observed cooling in regions like Russia and Scandinavia is linked to the weakening vortex. It turns out to be most,” says co-author Judah Cohen from Atmospheric and Environmental Research/Massachusetts Institute of Technology (US). “Several types of weather extremes are on the rise with climate change, and our study adds evidence that this can also include cold spells, which is an unpleasant surprise for these regions.” The effect is stronger over Asia and Europe than over the US. “Circulation patterns drive our weather”   “It is very important to understand how global warming affects circulation patterns in the atmosphere,” says co-author Dim Coumou from Vrije Universiteit Amsterdam, Netherlands. “Jet Stream changes can lead to more abrupt and surprising disturbances to which society has to adapt. The uncertainties are quite large, but global warming provides a clear risk given its potential to disturb circulation patterns driving our weather – including potentially disastrous extremes.”

[chubbs]

On 9/24/2017 at 3:36 PM, bluewave said:

https://www.pik-potsdam.de/news/press-releases/winter-cold-extremes-linked-to-high-altitude-polar-vortex-weakening

Some regions like Western Siberia even show a downward temperature trend in winter. In stark contrast, the Arctic has been warming rapidly. Paradoxically, both phenomena are likely linked: When sea-ice North of Scandinavia and Russia melts, the uncovered ocean releases more warmth into the atmosphere and this can impact the atmosphere up to about 30 kilometers height in the stratosphere disturbing the polar vortex. Weak states of the high-altitude wind circling the Arctic then favors the occurrence of cold spells in the mid-latitudes. Previous work by Kretschmer and colleagues identified this causal pathway in observational data and it is further supported by several climate computer simulation studies.

“Our latest findings not only confirm the link between a weak polar vortex and severe winter weather, but also calculated how much of the observed cooling in regions like Russia and Scandinavia is linked to the weakening vortex. It turns out to be most,” says co-author Judah Cohen from Atmospheric and Environmental Research/Massachusetts Institute of Technology (US). “Several types of weather extremes are on the rise with climate change, and our study adds evidence that this can also include cold spells, which is an unpleasant surprise for these regions.” The effect is stronger over Asia and Europe than over the US. “Circulation patterns drive our weather”   “It is very important to understand how global warming affects circulation patterns in the atmosphere,” says co-author Dim Coumou from Vrije Universiteit Amsterdam, Netherlands. “Jet Stream changes can lead to more abrupt and surprising disturbances to which society has to adapt. The uncertainties are quite large, but global warming provides a clear risk given its potential to disturb circulation patterns driving our weather – including potentially disastrous extremes.”

Starting off like many recent cool seasons