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Posts tagged with "hurricanes"

Sea Surface Temperature and Hurricanes

Tuesday, 4. November 2008, 16:45:02

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Is there a causal connection between warming tropical sea surface temperatures and Atlantic hurricane activity? This question has been asked several times over the last few years, especially after the record-breaking hurricane season of 2005. There seems to be a general consensus that sea surface temperatures play an important role - BUT...

Is it the local sea surface temperature in the Atlantic in isolation, or is it the sea surface temperature in the Atlantic 'relative' to the rest of the tropics, that drives variations in Atlantic hurricane activity?

If it is the relative sea surface temperature that matters, then the future is similar to the recent past, with periods of higher and lower hurricane activity relative to present-day conditions due to natural climate variability, but with little long-term trend. (All sea surface temperatures rises due to global warming).

If however the local sea surface temperature in the Atlantic in isolation causes increased hurricane activity it would (combined with rising sea levels) have dramatic implications for residents of regions impacted by Atlantic hurricanes - provided that global warming continues.

In a paper published in the journal Science Vecchi et al. discuss hurricane data observed over more than 50 years. Although differing interpretations of the observational record can imply vastly different futures for Atlantic hurricane activity due to global warming, they come to the conclusion, that so far the data can be interpreted both ways - either interpretation are statistically indistinguishable.

Whither Hurricane Activity? by Vecchi et al, Science 31 October 2008, Vol. 322. no. 5902, pp. 687 - 689 - DOI: 10.1126/science.1164396

• http://www.terradaily.com/reports/Contrasting_Hurricane_Theories_Heat_Up_999.html
• http://www.sciencemag.org/cgi/content/summary/322/5902/687





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Forgotten Hurricanes

Saturday, 4. October 2008, 14:49:42

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Hurricanes are front page news for a week or so, but a month later most of the world have forgotten that they ever occurred.

According to my local TV station (of 4 October 2008 that is) a medical team from Doctors Without Borders have found a village in Haiti completely under water after the hurricane Ike passed by about a month ago. (See a.o. USA Today of 8 September 2008).

For four weeks by now the 2400 inhabitants of the submerged village Mamont have been completely without help from the outside world, cut off as they were from greater towns. This means without drinking water and medical care.

Find the news item from MSF itself (Médecins Sans Frontières/Doctors Without Borders) of yesterday 3 October 2008 with further details here.

There is no need to stress that the situation in the area is still dramatic, and apart from the more immediate need there is also the risk of diseases spreading.



Haiti seems to suffer a seemingly disproportionate number of natural disasters like flooding. Why? Certainly not only because of the location in a hurricane prone area. In large part situations like now in Mamont are not natural disasters, but human-caused disasters. Haiti is the poorest nation in the Western Hemisphere. With oil too expensive for the impoverished nation, charcoal from burnt trees has provided 85% or more of the energy in Haiti for decades. As a result, Haiti's 8 million poor have relentlessly hunted and chopped down huge amounts of forest, leaving denuded mountain slopes that rainwater washes down unimpeded. Back in 1980, Haiti still had 25% of its forests, allowing the nation to withstand heavy rain events like 1987's Category 3 Hurricane Emily, without loss of life. But as of 2004, only 1.4% of Haiti's forests remained. It doesn't even take a tropical storm to devastate Haiti. In May of 2004, three days of heavy rains from a tropical disturbance dumped more than half a metre of rain in the mountains, triggering floods that killed over 2600 people. (Main source: NOAA)

What can be done to reduce these human-worsened natural disasters? Education and poverty eradication are critical to improving things. In addition, reforestation efforts and promotion of alternative fuels are needed.

PS: Do not expect to hear much from me for the next month or so, as I shall be away from home most of the time.



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Nargis follow-up

Saturday, 3. May 2008, 08:48:53

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At the time of writing the Severe Cyclonic Storm NARGIS is passing over Yangon (Rangoon). It stayed more or less on the course I mentioned a few days ago (See this post). Late Friday night it hit the Myanmar coast with wind-speeds around 210 km/h. Up to 7.45 million people may be affected by wind speeds of hurricane strength or above. In addition, 1.78 million people are living in coastal areas below 5 m and may therefore be affected by storm surge.

The storm made landfall around the mouth of the Ayeyawaddy (Irrawaddy) river, about 220 kilometres Southwest of Yangon, before hitting the country's economic hub. Meteorologists have warned of a tidal surge up to 3.5 metres due to the cyclone.

It is still too early to get an overview over damage and casualties. Myanmar has been ruled by the military since 1962 and the junta restricts media activities, so information could be slow in coming out. It is not known whether damage from the storm would affect a referendum next Saturday on a new constitution which the ruling junta says will pave the way for democratic elections in 2010. No doubt the damage will be extensive as the cyclone passed through many densely populated areas. It obviously wreaked havoc in Yangon (where the airport was closed and electricity fell out) and the Irrawaddy delta town of Bassein.

Cyclone Nargis missed neighbouring Bangladesh, where fishing crews were told to stay close to shore and not to venture into the Bay of Bengal, after fears the storm would slam into the Southeast coast.

• http://ap.google.com/article/ALeqM5greyFH3qkj9mc9oagSoulgjN4KHgD90E15LO0
• http://www.reliefweb.int/rw/RWB.NSF/db900SID/MUMA-7EAAR3?OpenDocument
• http://afp.google.com/article/ALeqM5h5kIScmy1U7oTnHZjavFOqWLKmtA
• http://www.hindu.com/thehindu/holnus/003200805031021.htm
• http://www.terradaily.com/reports/Cyclone_to_hit_Bangladesh_and_Myanmar_coast_official_999.html
• http://earthobservatory.nasa.gov/NaturalHazards/shownh.php3?img_id=14809

Ole


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Tropical Cyclone NARGIS-08

Tuesday, 29. April 2008, 19:03:58

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The tropical cyclone Nargis in the Bay of Bengal is on course towards the west coast of Myanmar. It is expected to hit the lowest central part of the country, the Ayeyarwady (or Irrawaddy) delta near the great city of Yangon (also known as Rangoon) and the low coast to the north of it. In the northern hemisphere a cyclone rotates counter-clockwise, because of the coriolis force, which means that water masses from the Bay of Bengal will be forced far over land on the right side of the cyclone, where the delta is. Further north the mountain range Arakan Yoma (also known as the Chin Hills) forms a wall towards the bay, and here Nargis is expected to release torrential rains, when the humid air is forced up over the up to 3000 m high mountain tops.

The majority of Burma's Myanmar's population lives in the Ayeyarwady valley. The upper and central portions of the Ayeyarwady delta are almost entirely under cultivation, principally for rice. The climate is monsoonal climate, with an average annual rainfall of about 1,500-2,000 mm in the north increasing to 2,500 mm in the southeast and 3,500 mm in the southwest. Over 90% of the rain falls between mid May and mid November.

Sorry at my age we sometimes have difficulties with "new" geographical names, but I do my utmost to keep to the official, politically correct, spelling.

• http://www.gdacs.org/reports.asp?eventType=TC&ID=NARGIS-08&system=asgard&alertlevel=Green&glide_no=&location=&country=&new=true
• http://www.arcbc.org.ph/wetlands/myanmar/mmr_irrdel.htm



PS of 30 April 2008
Bangladesh raises storm alert and urges swift rice harvest: http://www.alertnet.org/thenews/newsdesk/DHA224084.htm
The cyclone can also be tracked here, with up to 72 hours lead: http://tsr.mssl.ucl.ac.uk/

PS of 3 May 2008: See follow up here.

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Warmer Seas and Hurricanes

Friday, 1. February 2008, 09:40:14

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Many researchers believe warming is causing Atlantic hurricanes to get stronger, while others aren't so sure. As late as last week U.S. researchers challenged the view that as hurricanes feed on warm water global warming would lead to more powerful storms - saying global warming could reduce the number of hurricanes hitting the United States with warmer waters resulting in atmospheric instabilities that prevent storms from forming.

According to an article published yesterday, 31 January 2008, in Nature sea surface warming contributes largely to the recent increase in Atlantic hurricane activity. I am referring to Large contribution of sea surface warming to recent increase in Atlantic hurricane activity by Saunders & Lea.

The researchers claim that 0.5°C increase in sea surface temperature is associated with a 40 percent increase in hurricane frequency and activity. They showed that ocean warming is directly linked to the frequency, strength and duration of hurricanes. The authors looked at storms that formed in the tropical North Atlantic, Caribbean Sea and Gulf of Mexico - a region that produced nearly 90 percent of the hurricanes that struck the United States between 1950 and 2005. The results refer to increase in hurricane activity relative to the fifty year (1950-2000) average between 1996 and 2005.

In the period 1950-2000 there were around six hurricanes per year on average, roughly half of which were intense hurricanes. But for the 10 years from 1996 to 2005, the tally rose to about eight hurricanes per year, about four of which were intense ones. After stripping out the role of wind in hurricane generation, the researchers calculate that an increase of 0.5 degrees Celsius was responsible for about 40 percent of the rise in hurricane activity.

The paper could be a major contribution to scientists struggling to understand impacts from global warming.

• http://www.nature.com/nature/journal/v451/n7178/abs/nature06422.html
• http://www.scientificblogging.com/news_releases/study_links_north_atlantic_sea_surface_temperature_and_hurricane_activity_0
• http://www.terradaily.com/reports/Warmer_seas_boosted_hurricane_frequency_by_40_percent_study_999.html
• http://www.eurekalert.org/pub_releases/2008-01/ucl-iha012808.php
• http://www.guardian.co.uk/feedarticle?id=7268579
• http://www.sciencedaily.com/releases/2008/01/080130130647.htm
• http://physicsworld.com/cws/article/news/32646;jsessionid=301BEAC2887974FB134045748FF44F28




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Powerful Atlantic Hurricanes

Saturday, 1. December 2007, 10:50:48

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After the record-breaking hurricane season in 2005 it was suspected that global warming is leading to stronger and more frequent tropical storms (hurricanes, typhoons, and cyclones). Satellites have only given us sufficient data over the last twenty years or so, but nevertheless recently documented trends in the existing records of hurricane intensity and their relationship to increasing sea surface temperatures suggest that hurricane intensity may be increasing due to global warming. It seems however that the Atlantic is more vulnerable to climate change than the Pacific and the Indian Ocean.

According to a paper published on 29 November 2007 in the Bulletin of the American Meteorological Society warmer ocean water is only part of the story. Wind and precipitation over the ocean also play their role. The atmosphere and the ocean interact with each other in a distinct way creating a special basin wide north south circulation pattern, called Meridional Mode (meaning along longitudinal meridians and thus north/south and south/north directed).

In a study published in February 2007, Kossin and his co-authors created a record of hurricane data that accounted for the significant improvement in storm detection that followed the advent of weather satellites. An analysis of this recalibrated data showed that hurricanes have become stronger and more frequent in the Atlantic Ocean over the last two decades. The increasing trend, however, is harder to identify in the world's other oceans. The other oceanic basins have their own modes of ocean-atmosphere variability.

Because higher sea surface temperatures in the Atlantic act in concert with the Atlantic Meridional Mode, Vimont and Kossin suggest that Atlantic hurricanes will be more sensitive to climate changes than storms in other ocean basins.

• http://ams.allenpress.com/perlserv/?request=get-abstract&doi=10.1175%2FBAMS-88-11-1767
• http://www.news.wisc.edu/14493
• http://www.physorg.com/news115574276.html
• http://www.sciencedaily.com/releases/2007/11/071129183753.htm
• http://www.terradaily.com/reports/Recipe_For_A_Storm_The_Ingredients_For_More_Powerful_Atlantic_Hurricanes_999.html
• http://www.agu.org/pubs/crossref/2007/2007GL029683.shtml
• http://www.aos.wisc.edu/~dvimont/Research/


Meridional: In meteorology, a flow, average, or functional variation taken in a direction that is parallel to a line of longitude; along a meridian; northerly or southerly; as opposed to zonal.

Meridian: An imaginary great circle on the earth's surface passing through the North and South geographic poles. All points on the same meridian have the same longitude.




climate change, oceanography, hurricanes

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