Thursday, May 1, 2008

Jet Streams Are Shifting And May Alter Paths Of Storms And Hurricanes

Jet Streams Are Shifting And May Alter Paths Of Storms And Hurricanes

ScienceDaily (Apr. 17, 2008) The Earth's jet streams, the high-altitude bands of fast winds that strongly influence the paths of storms and other weather systems, are shifting--possibly in response to global warming. Scientists at the Carnegie Institution determined that over a 23-year span from 1979 to 2001 the jet streams in both hemispheres have risen in altitude and shifted toward the poles. The jet stream in the northern hemisphere has also weakened. These changes fit the predictions of global warming models and have implications for the frequency and intensity of future storms, including hurricanes.

Cristina Archer and Ken Caldeira of the Carnegie Institution's Department of Global Ecology tracked changes in the average position and strength of jet streams using records compiled by the European Centre for Medium-Range Weather Forecasts, the National Centers for Environmental Protection, and the National Center for Atmospheric Research. The data included outputs from weather prediction models, conventional observations from weather balloons and surface instruments, and remote observations from satellites.

Jet streams twist and turn in a wide swath that changes from day to day. The poleward shift in their average location discovered by the researchers is small, about 19 kilometers (12 miles) per decade in the northern hemisphere, but if the trend continues the impact could be significant. "The jet streams are the driving factor for weather in half of the globe," says Archer. "So, as you can imagine, changes in the jets have the potential to affect large populations and major climate systems."

Storm paths in North America are likely to shift northward as a result of the jet stream changes. Hurricanes, whose development tends to be inhibited by jet streams, may become more powerful and more frequent as the jet streams move away from the sub-tropical zones where hurricanes are born.

The observed changes are consistent with numerous other signals of global warming found in previous studies, such as the widening of the tropical belt, the cooling of the stratosphere, and the poleward shift of storm tracks. This is the first study to use observation-based datasets to examine trends in all the jet stream parameters, however.

"At this point we can't say for sure that this is the result of global warming, but I think it is," says Caldeira. "I would bet that the trend in the jet streams' positions will continue. It is something I'd put my money on."

The results are published in the April 18 Geophysical Research Letters.

Weather Note

Here are three vidoes from the April 28th twister that struck Virginia...
As they say pictures can tell the story....


Fatigue Study - 27 April 2008

A new study has been released by the Centre for Occupational and Health Psychology, at Cardiff University, entitled "Fatigue and health in a seafaring population", by Emma J. K. Wadsworth, Paul H. Allen, Rachel L. McNamara and Andrew P. Smith.

Background Occupational fatigue is relatively common within the general population and has been linked to reduced performance, injury and longer term ill-health. Despite growing acknowledgement of this problem in the maritime sector, little research has been conducted into the risk factors, prevalence and consequences of seafarers' fatigue.

Aims To examine the prevalence of fatigue among seafarers, identify potential risk factors and assess possible links with poor performance and ill-health.

Methods Cross-sectional questionnaire survey of seafarers working in the offshore oil support, short-sea and deep-sea shipping industries. A number of tools were used including the fatigue subscale of the profile of fatigue-related symptoms, the Cognitive Failures Questionnaire, the General Health Questionnaire and the SF36 General Health scale.

Results In all, 1855 questionnaires were completed giving an overall response rate of 20%. Fatigue symptoms were associated with a range of occupational and environmental factors, many unique to seafaring. Reporting a greater number of risk factors was associated with greater fatigue [e.g. OR = 2.53 (1.90–3.35) for those with three or four risk factors and OR = 9.54 (6.95–13.09) for those with five or more risk factors]. There was also a strong link between fatigue and poorer cognitive and health outcomes, with fatigue the most important of a number of risk factors, accounting for 10–14% of the variance.

Conclusions Seafarers' fatigue could impact on safety within the industry and may be linked to longer term individual ill-health. It can only be addressed by considering how multiple factors combine to contribute to fatigue.