Jet stream moved northwards 270 miles in 22 years; climate change to blame?
Climate change is forcing the jet stream higher and closer to the pole in both the Northern and Southern Hemisphere, according research published this April in the journal Geophysical Research Letters. In their paper, "Historical trends in the jet streams", researchers Cristina Archer and Ken Caldeira of Stanford's Carnegie Institution of Washington analyzed data from 1979-2001, and found that the Northern Hemisphere jet stream moved northward at approximately 125 miles per decade (270 miles during the 22-year period of the study). The jet moved higher by 5-23 meters during this period, and the wind speeds decreased by about 1 mph. Archer and Caldeira's study confirms other research showing a poleward movement of the jet stream in recent decades (Fu et al., 2006; Hu and Fu, 2007). All of these changes are consistent with the behavior of the jet stream predicted by global warming theory. For example, Lorenz and DeWeaver (2007) found poleward shifts of the jet stream by 2100 in the forecasts of 15 climate models used to formulate the "official" word on climate, the 2007 Intergovernmental Panel for Climate Change (IPCC) report. However, the authors were careful not to say how much of this shift in the jet stream was due to natural causes versus human-caused climate change. It is unknown if the jet stream has natural decades-long changes in its path that could account for the observed poleward shift.
Figure 1. The jet stream is located where the strongest winds at the top of the troposphere are found (35,000-45,000 feet high, 200-300 mb in pressure).
Archer and Caldeira note that "These changes in jet stream latitude, altitude, and strength have likely affected, and perhaps will continue to affect, the formation and evolution of storms in the mid-latitudes and of hurricanes in the sub-tropical regions." They don't specify what these changes might be. There is very little research that has been done suggesting how changes in the jet stream might affect hurricane formation and strength. One effect we may begin to see in coming decades is a reduction and/or delay in the number of hurricanes that recurve northward out to sea. Recurvature occurs when a hurricane begins to "feel" the westerly winds of the jet stream. As the jet stream continues to move northward and weaken as the globe warms, we can expect that hurricanes moving though the Caribbean will be less likely to recurve, resulting in more hurricane strikes in Mexico and Central America. Unfortunately, the quality of the Atlantic hurricane database for non-U.S. landfalls is not very good, and it will be several decades before we will be able to tell if the number of hurricane landfalls in Mexico and Central America is increasing due to a poleward shift in the jet stream.
References
Fu, Q., C. M. Johanson, J. M. Wallace, and T. Reichler (2006), Enhanced mid-latitude tropospheric warming in satellite measurements, Science, 312, 1179, doi:10.1126/science.1125566.
Hu, Y., and Q. Fu (2007), Observed poleward expansion of the Hadley circulation since 1979, Atmos. Chem. Phys. Disc., 7, 9367.9384.
Lorenz, D. J., and E. T. DeWeaver (2007), Tropopause height and zonal wind response to global warming in the IPCC scenario integrations, J. Geophys. Res., 112, D10119, doi:10.1029/2006JD008087.
Jeff Masters
Reader Comments
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Just looking at the latest satellite imagery for the ULL, it appears that the Cuba thunderstorms have been moving towards the circulation over the past couple hours. Yet to be seen if this activity does indeed get wrapped around the ULL, but if it does, that would be terrific.
Although I am careful for what I wish for....the white rabbit taught me that
Unfortunately the ULL is only pulling on the cirrus tops of the thunderstorms. Those storms over Cuba are land-based and cannot be pulled off over water for very long before dying off. Also as I already said the ULL is only pulling the cirrus tops, not the whole thunderstorm, so the whole thing can't be pulled off of Cuba anyway.
http://www.wunderground.com/radar/radblast.asp?ID=AMA
Probably either one. It would be hard to appoint someone worse than Michael Brown.
Also - Thanks to 456 for his informative blog on easterly waves!
the best thing you can do for you and your family is to prepare on your own like the government is never going to come. surfmom has set the bar high this year!
(also see patrap's preparedness website)
"Brownie, you're doing a heck of a job,"
going back to help friends after frances and Jeanne was a real eye opener. I drove up and down all the streets, looked at what worked, what didn't work, what people had that made their quality of life at a difficult time better -
/just like my brother's! :)
State environmental department spokesman Dennis Schain says the lightning struck shortly after 5 p.m. Sunday. He says one of the victims at Hammonasset Beach State Park is "very seriously" injured.
Strong thunderstorms moved through the state Sunday afternoon. Thousands of people in Connecticut lost power.
I dunno......it's possible......here's the same storms from another radar, though they're near the edge of the scanning range.
Both radars are reporting VILs of 75+ though, which means those storms are generating enormous hail (4+ inches) no matter how strong the echoes are.
Ur post is solid with me. But an upper level ridge (anticyclone) should result when a warm-core develops in the upper levels due to expansion of geopotential heights* over the disturbance relative to the surrouding enviroment.
*This expansion occurs due to expanding air within the warm-core.
Just my little addon.
Can anyone see me here? Thanks!
Clearly visible
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