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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TTAA00 KNHC DDHHMM
TROPICAL WEATHER OUTLOOK
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
500 PM PDT FRI JUN 6 2008
FOR THE EASTERN NORTH PACIFIC...EAST OF 140 DEGREES WEST LONGITUDE..
1. AN AREA OF SHOWERS AND THUNDERSTORMS EXTENDS FROM THE GULF OF
TEHUANTEPEC SOUTHWARD FOR SEVERAL HUNDRED MILES OVER THE EASTERN
PACIFIC. THERE ARE NO SIGNS OF ORGANIZATION AND DEVELOPMENT...IF
ANY...SHOULD BE SLOW TO OCCUR.
TROPICAL CYCLONE FORMATION IS NOT EXPECTED DURING THE NEXT 48 HOURS.
DDR, glad to hear that. I had a "trace" half hour ago. But I do expect some decent showers late tonight, and tomorow. I long to hear the water pouring into the tanks.......
Thanks 456. Eagerly looking forward to that " bulf " of rain LOL
lol
SPC Storm Reports
Hi Taz. How you do ?
We look to be getting some rains, you and I, if the dry air allows this wave to hold on overnight. What is your take on the situation ?
hurricanes in the gulf is not welcome this year or will be looking at $6 gas or more
hi pot
Lightning Strikes - in the last hour
Yellow strokes are Intra or Inter-Cloud (IC)
Red strokes are Cloud-To-Ground (CG)
The humidity has gone from 69% at 6:oo, to 97% !! now according to piarco.
Pressure is up by 1 , to 1014 and rising, strangely enough.
where the commets i posted be for???
Well I am not really looking at the shear now. Unless we have a July like 2005, which I think is unlikely, I will start paying attention to shear in August, and what degree each storm is facing in its path and at that time.
lol. one after the other after the other after the other.
A strong tropical wave is moving over the island.
Weather: Tonight: Cloudy with showers and isolated thunderstorms.
Tomorrow: Cloudy to overcast with moderate to heavy showers, scattered thunderstorms and occasional gusty winds.
pottery,it drizzled twice then stoped,it looks like south trinidad will get the most rain tonight.
Its the confusion brought about by rain falling on my head.
Sorry about that.
There must be an awful lot of energy being created and things could change really fast there I think.
This is not the ITCZ is it ? Cant have jumped that far north overnight??
...ITCZ...
ITCZ AXIS IS CENTERED ALONG 4N8W 5N14W 4N19W 6N25W 4N32W INTO NE
BRAZIL NEAR 2N51W. CLUSTERS OF SCATTERED MODERATE/ISOLATED
STRONG CONVECTION ARE FROM 1N TO INLAND OVER SW AFRICA BETWEEN
THE PRIME MERIDIAN AND 11W AND WITHIN 120 NM OF LINE FROM 5N31W
5N44W TO 10N54W. SCATTERED CLUSTERS OF SIMILAR CONVECTION ARE
FROM 1N-8N BETWEEN 11W-21W.
The convection around 8N, 32W is another Twave
TROPICAL WAVE IS SLIGHTLY TILTED TO THE NE FROM 3N27W TO 12N25W
MOVING W NEAR 10 KT. THE WAVE CONTINUES TO BE ILL-DEFINED AND
WAS RELOCATED BASED ON THE MIMIC-TPW ANIMATION ALONG THE PEAK
MOISTURE CURVATURE. HOWEVER...SATELLITE IMAGERY SHOWS NO DEEP
CONVECTION WITH BROKEN/OVERCAST LOW/MID CLOUDS WITH ISOLATED
SHOWERS WITHIN 120 NM EITHER SIDE OF THE WAVE AXIS.
Meanwhile,the dry air over the Trop. Atl all the way to Africa is retreating fast. And a very large body of wet air is at 10 n just about to exit Africa. Looking good for the next feature there.
Viewing: 751 - 801
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