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Storms in the Mediterranean, a sea of uncertainty

In Barcelona (Spain), about 250 experts have recently debated about the possible future scenarios of storms in the Mediterranean. Scientists still don’t dare to assure that the frequency of these episodes will increase. At the moment, the scientific community is sailing on a sea of uncertainty. They can only assure that the impact will be important due to the excessive urbanization of the coast.

Patricia Morén | 14 september 2009

Each year there are about 14 million storms in the world. In total there are 40,000 per day, often with a disastrous impact for the population and the affected area. The scientific community still doesn’t quite know what will happen with the Mediterranean storms as it is a region of unstable weather and erratic rainfall where these episodes of adverse weather conditions are frequent. In Catalonia (Spain) for example, we find an average of 130 days of storms per year, with more than100,000 related lightning.

Photo: Juan Francisco Lladó Sabater
Will this average be maintained? "More studies are needed to know what will happen with the Mediterranean storms. At the moment we are not really sure if its frequency is increasing, but we do have proof that shows what the impacts and damages are", says Carmen Llasat, from the Department of Astronomy and Meteorology from the University of Barcelona (UB), director of the Group of Analysis of Adverse Weather Conditions (GAMA) and coordinator of the 11th Plinius Conference on Mediterranean storms.

Urbanization and new land uses

Today, the ravages of storms are not so much the result of natural phenomenon itself. Responsibility lies with the growing human densification of the coastal areas of natural risk (when storms are at sea) and recreation areas (when they come from mountains), explains Llasat.
The responsibility of the damages of the storms falls on to the increasing human densification. According to Jordi Salat, oceanographer at the Marine Science Institute, the coastal system is kind of complex because not only are the sediments of the area involved but also the animal populations and marine plants “They seem not to do anything but they protect us. This natural barrier defends us from the attacks of the sea, but trying to colonize the waterfront gives us problems”, explains the scientist. The explanation is simple: the sea will always try to return to its natural place, the same way it happens when the course of a river is changed and there are floods.

Rainfalls of certain intensity, of more than 30 litres per square metre in an hour, can cause landslides of different types, immediate or delayed in time. Therefore, if in the future storms increase, the geological risk would also increase. Currently man is occupying areas with possible landslides and suffers its consequences more “not because there are more, but because the risk areas have been urbanized, and that is independent from more or less rainfall”, says Joan Manuel Vilaplana, director of the Geodynamics and Geophysics Department of the Geology Faculty of the UB and RISKNAT.

With the urbanization of land, the change in the use of land (of forest areas into agricultural areas) can also promote landslides. "In Europe, a small place with more and more people, we have failed. It shouldn’t be allowed to build in an area unsafe to natural hazards”, claims Vilaplana. He also says that "the impact of a natural phenomenon depends on a simple equation: the severity of this phenomenon, the physic and social vulnerability of the land and the exposition grade of this vulnerable element".

This way, the impact of the storms is also uneven in the different Mediterranean basins. Llasat informs that in the northern European basins the damage is mostly material and the few fatal victims occur because of carelessness or ignorance before a storm. But in the southern basin, in the African countries the population is more exposed and therefore more vulnerable. In Algeria 600 people have died in a day because of a storm. Science invites thought.

More storms?

Damages apart, experts predict trends in storms. “Everybody talks about the climate change, but when people do, they refer to the one induced by humans as the global weather is always subject to change”, says Bruce D. Malamud, from the Division of Natural Hazards from the European Geosciences Union. According to the expert, climate change caused by the action of man will bring along more natural hazards. In reference to the storms, Malamud explains: "there will be a major tendency to heat. Therefore, there will be more storms if the temperature and the emission of greenhouse gases towards the atmosphere go on increasing because of human activity. However, we don’t know the magnitude”. Uncertainty lies in the use of different predictive models

The European data base MEDEX (MEDiterranian EXperimental), a retrospective study between the years 1957 and 2000, or the predictive models like the one of Piero Lionello, from the Materials Science Department of the University of Lecce (Italy), allow to take conclusions in this sea of uncertainty. In the western Mediterranean area a decrease in the frequency of depressions has been detected, whilst they increase in the east. This phenomenon could be related to global warming. This minor frequency of depressions will translate into less rainfalls in the Mediterranean and therefore in more episodes of drought. It is still unclear if the intensity of the rainfalls, already intense, will increase or decrease although “there are reasons to believe it will increase”, informs Agustí Jansà, delegate to the State Meteorology (AEMET) in the Balearic Islands and coordinator of the project.

Lightning to prevent floodsLightning, infallible natural indicators of the location of a storm, can also be used to predict in a quicker and better way where heavy precipitations and unexpected floods will take place. This is the goal of the European project FLASH (Flash Flood and Lightning), created in 2006 with the participation of the University of Barcelona.

Lightning works like a radio station. They emit radio waves that can travel very fast through the Mediterranean and through Europe and can monitor thousands of kilometres away. The FLASH project uses the Zeus Lightning Network, a network installed in Greece consisting of six sensors and prepared to capture the lightning signs that come from the sea. An algorithm has also been developed and a software to estimate the direction and speed of the storms.

Due to the data about lightning being updated every 15 minutes, meteorological predictions on storms and unexpected floods could be done every three hours. These predictions could be spread in (nowcasting), in stead of every 24 or 48 hours (forecasting), so that the FLASH model could do better weather predictions.


1 comment

Maria del mar 18/10/2010
cuando es mas tipico k haya tormentas en el mediterraneo?

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