PGR News from the Pacific

Posted 4:25 PM by Tevita

Global warming 'induces fewer, but meaner, cyclones'

From : Sci Dev. Net

Adverse wind conditions may reduce the frequency of tropical cyclones due to global warming — but those forming will be stronger, researchers say.

The findings are contrary to the widely held theory that global warming will increase the frequency of tropical cyclones, known as hurricanes in the Atlantic Ocean.

A team led by David Nolan from the University of Miami in the United States developed new computer-based models to predict the impact of warmer ocean temperatures and wind conditions on tropical cyclones.

The models showed that, as expected, the frequency of tropical storms increased with warmer ocean temperatures. But when 'wind shear' — the change in wind direction and speed with height — was studied they found that, as water temperature increased, the shear helped suppress formation of hurricanes to a greater extent.

"We expected to find that when oceans warm, hurricanes would form more quickly, even in the presence of adverse wind conditions we call wind shear," says Nolan. "Instead we found the opposite: adverse wind shear did more damage to developing storms when sea surface temperature was increasing."

Ocean temperatures and wind shear are considered the two most important factors for predicting hurricanes, both in regular weather prediction studies and climate change studies.

Nolan says the new models are complementary to existing ones, which are able to simulate global weather but do not simulate hurricanes accurately. In contrast, the new models are able to simulate hurricanes in small localities.

The study was published in Geophysical Research Letters (July 2008). The researchers hope their model will lead to a better understanding of the relationship between climate and global hurricane activity.

In a separate study, reported in the August issue of the same journal, Brazilian and Indian scientists noted a decrease in easterly wind shear in the tropics, favouring the formation of strong cyclones.

The study notes that, for the first time in recorded history, a category five tropical hurricane formed in June 2007 together with two more severe tropical storms over the northern Indian Ocean.

Tropical cyclones in the Bay of Bengal region usually occur in the non-monsoon months. But the researchers suggest that if the weakening trend continues, there could be more severe cyclones, even during the summer monsoon months of June to September.

References
Geophysical Research Letters, doi 10.1029/2008GL034147 (2008)

Geophysical Research Letters, doi 10.1029/2008GL034729 (2008)



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Net Adverse wind conditions may reduce the frequency of tropical cyclones due to global warming — but those forming will be stronger, researchers say. The findings are contrary to the widely held theory that global warming will increase the frequency of tropical cyclones, known as hurricanes in the Atlantic Ocean. A team led by David Nolan from the University of Miami in the United States developed new computer-based models to predict the impact of warmer ocean temperatures and wind conditions on tropical cyclones. The models showed that, as expected, the frequency of tropical storms increased with warmer ocean temperatures. But when 'wind shear' — the change in wind direction and speed with height — was studied they found that, as water temperature increased, the shear helped suppress formation of hurricanes to a greater extent. "We expected to find that when oceans warm, hurricanes would form more quickly, even in the presence of adverse wind conditions we call wind shear," says Nolan. "Instead we found the opposite: adverse wind shear did more damage to developing storms when sea surface temperature was increasing." Ocean temperatures and wind shear are considered the two most important factors for predicting hurricanes, both in regular weather prediction studies and climate change studies. Nolan says the new models are complementary to existing ones, which are able to simulate global weather but do not simulate hurricanes accurately. In contrast, the new models are able to simulate hurricanes in small localities. The study was published in Geophysical Research Letters (July 2008). The researchers hope their model will lead to a better understanding of the relationship between climate and global hurricane activity. In a separate study, reported in the August issue of the same journal, Brazilian and Indian scientists noted a decrease in easterly wind shear in the tropics, favouring the formation of strong cyclones. The study notes that, for the first time in recorded history, a category five tropical hurricane formed in June 2007 together with two more severe tropical storms over the northern Indian Ocean. Tropical cyclones in the Bay of Bengal region usually occur in the non-monsoon months. But the researchers suggest that if the weakening trend continues, there could be more severe cyclones, even during the summer monsoon months of June to September. References Geophysical Research Letters, doi 10.1029/2008GL034147 (2008) Geophysical Research Letters, doi 10.1029/2008GL034729 (2008) * Comments: Post a Comment	Archive October 2002 November 2002 December 2002 January 2003 February 2003 March 2003 April 2003 May 2003 June 2003 July 2003 August 2003 September 2003 October 2003 November 2003 December 2003 January 2004 February 2004 March 2004 April 2004 May 2004 June 2004 July 2004 August 2004 September 2004 October 2004 November 2004 December 2004 January 2005 February 2005 March 2005 April 2005 May 2005 June 2005 July 2005 August 2005 September 2005 October 2005 November 2005 December 2005 January 2006 February 2006 March 2006 April 2006 May 2006 June 2006 July 2006 August 2006 September 2006 October 2006 November 2006 December 2006 January 2007 February 2007 March 2007 April 2007 May 2007 June 2007 July 2007 August 2007 September 2007 October 2007 November 2007 December 2007 January 2008 February 2008 March 2008 April 2008 May 2008 June 2008 July 2008 August 2008 September 2008 October 2008 November 2008 December 2008 January 2009 February 2009 March 2009 April 2009 May 2009 June 2009 July 2009 August 2009 September 2009 October 2009 November 2009 January 2010 RSS Feed Alternative feed Contact Tevita Something new: Agrobiodiversity Weblog: For discussions of conservation and sustainable use of the genetic resources of crops, livestock and their wild relatives. 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