Jul 30 2007
Tropical cyclones over the Mediterranean Sea in climate change simulations
Gaertner, M. A., D. Jacob, V. Gil, M. Dominguez, E. Padorno, E. Sanchez, and M. Castro (2007), Tropical cyclones over the Mediterranean Sea in climate change simulations [PDF, requires subscription], Geophys. Res. Lett., 34, L14711, doi:10.1029/2007GL029977.
Tropical cyclones form only under specific environmental conditions. Anthropogenic climate change might alter the geographical areas where tropical cyclones can develop. Using an ensemble of regional climate models, we find an increase in the extremes of cyclone intensity over the Mediterranean Sea under a climate change scenario. At least for the most sensitive model, the increase in intensity is clearly associated with the formation of tropical cyclones. Previous studies did not find evidence of changes in the projected areas of formation of tropical cyclones (Intergovernmental Panel on Climate Change, 2007; Walsh, 2004; Lionello et al., 2002). Those studies were based either on relatively low-resolution global climate models or on one particular regional climate model. The use of a multi-model ensemble of relatively high-resolution regional climate models has allowed us to detect for the first time a risk of tropical cyclone development over the Mediterranean Sea under future climate change conditions.
I am skepical that there will ever be any hurricanes in the Mediterranean Sea. All known tropical cyclones have developed in the tropics, where the mean flow is from east to west. The Mediterranean region, on the otherhand, has mean westerly mean flows, even in the summer months when potential tropical storms may develop. There is nothing that says a tropical storm needs to move from east to west, but since that is the mean flow in the tropics, that’s what happens. When the storms move to far north or south, they either get absorbed by the mean westerly flow or get intensified into a subtropical storm.
The Mediterranean Sea has it’s highest sea surface temperatures in the eastern region, near Israel and Egypt. Even now, these temperature are high enough, for a brief period of time during the summer, for tropical storm development. In global warming scenarios, the sea surface temperature of the Mediterranean will increase, and according to the authors, possibly result in tropical storm formation.
However, as I mentioned above, the mean flow is from west to east. The Western Mediterranean is very cool; it is not warm enough for tropical storm development. Even assuming a warming of 2C, this will not be warm enough. The only place for tropical storm development will be in the eastern part of the sea. However, since the mean flow is from west to east, there will probably not be enough time for development into hurricanes. Since these storm will not be in the tropics, they will technically be sub-tropical depressions and sub-tropical storms. It is my opinion that even under global warming scenarios sea, the meteorological conditions will not be favorable for hurricane development in the Mediterranean Sea.
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2 Responses to “Tropical cyclones over the Mediterranean Sea in climate change simulations”
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Hmm. Being Antipodean, I had never considered that in the Northern Hemisphere, “sub”-tropical meant *north* of the Tropic of Cancer. I suppose “sub-equatorial” is likewise topsy-turvy up there? Is this because north/south constraints are meaningless in the context of Earth in space, or because “supra-tropical” sounds silly?
I don’t know why, it just is.
(But probably that north/south thing.)