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Mediterranean tropical-like cyclones (sometimes called "medicanes", a portmanteau of the words Mediterranean and hurricane) are rare meteorological phenomena observed in the Mediterranean Sea. Due to the dry nature of the Mediterranean region, formation of tropical-like cyclones is infrequent, with only 100 recorded tropical-like storms between 1948 and 2014. No agency, however, is officially responsible for monitoring the formation and development of medicanes. Tropical-like cyclogenesis typically occurs within two separate regions of the sea. The first region, encompassing areas of the western Mediterranean, is more conducive for development than the other, the Ionian Sea to the east. The rough mountainous geography of the region raises additional difficulties despite being favorable for the development of severe weather and convective activity in general, and only with abnormal meteorological circumstances can medicanes form. Numerous studies have been conducted on the impact of global warming on Mediterranean tropical-like cyclone formation, generally concluding that fewer yet more intense storms would form. The development of tropical-like cyclones in the Mediterranean Sea can usually only occur under somewhat unusual circumstances. Low wind shear and atmospheric instability induced by incursions of cold air are often required. A majority of medicanes are also accompanied by upper-level troughs, providing energy required for intensifying atmospheric convection—thunderstorms—and heavy precipitation. The baroclinic properties of the Mediterranean region, with high temperature gradients, also provides necessary instability for the formation of tropical-like cyclones. Another factor, rising cool air, provides necessary moisture as well. Warm sea surface temperatures (SSTs) are mostly unnecessary, however, as most medicanes' energy is derived from warmer air temperatures. When these favorable circumstances coincide, the genesis of warm-core Mediterranean tropical-like cyclones, often from within existing cut-off cold-core lows, is possible in a conducive environment for formation. Several notable and damaging medicanes are known to have occurred. In September 1969, a north African Mediterranean tropical-like cyclone produced flooding that killed nearly 600 individuals, left 250,000 homeless, and crippled local economies. A medicane in September 1996 that developed in the Balearic Islands region spawned six tornadoes and inundated parts of the islands. Several medicanes have also been subject to extensive study, such as those of January 1982, January 1995, September 2006, and November 2011. The January 1995 storm is one of the best-studied Mediterranean tropical-like cyclones, with its close resemblance to tropical cyclones elsewhere and availability of observations. The medicane of September 2006, meanwhile, is well-studied due to availability of existing observations and data. In November 2011, the NOAA's Satellite Analysis Branch monitored a possible medicane, named Rolf by the Free University of Berlin (FU Berlin), though it ceased doing so the following month. No agency is officially responsible for monitoring the basin. == Climatology == Mediterranean tropical cyclones are not considered to be formally classified tropical cyclones and their region of formation is not officially monitored by any agency,. Although the Satellite Analysis Branch released information related to a medicane in November 2011 while it was active, it ceased doing so on 16 December 2011.〔 The Mediterranean Sea, however, lies within the Greek area of responsibility, while France's Météo-France National serves as a "preparation service" for the areas as well. A majority of Mediterranean tropical cyclones form over two separate regions. The first, more conducive for development than the other, encompasses an area of the western Mediterranean bordered by the Balearic Islands, southern France, and the shorelines of the islands of Corsica and Sardinia. The second identified region of development, in the Ionian Sea between Sicily and Greece and stretching south to Libya, is less favorable for tropical cyclogenesis. An additional two regions, in the Aegean and Adriatic seas, produce fewer medicanes, while activity is minimal in the Levantine region. The geographical distribution of Mediterranean tropical cyclones is markedly different from that of other cyclones, with the formation of regular cyclones centering on the Pyrenees and Atlas mountain ranges, the Gulf of Genoa, and the island of Cyprus in the Ionian Sea.〔Cavicchia et al. 2013, p. 7〕 Although meteorological factors are most advantageous in the Adriatic and Aegean seas, the closed nature of the region's geography, bordered by land, allows little time for further evolution.〔Cavicchia et al. 2013, p. 18〕 The geography of mountain ranges bordering the Mediterranean are conducive for severe weather and thunderstorms, with the sloped nature of mountainous regions permitting the development of convective activity.〔Homar et al. 2003, p. 1470〕 Although the geography of the Mediterranean region, as well as its dry air, typically prevent the formation of tropical cyclones, when certain meteorological circumstances arise, difficulties influenced by the region's geography are overcome.〔Emanuel 2005, p. 220〕 The occurrence of tropical cyclones in the Mediterranean Sea is generally extremely rare, with an average of 1.57 forming annually and merely 99 recorded occurrences of tropical-like storms discovered between 1948 and 2011 in a modern study, with no definitive trend in activity in that period.〔Cavicchia et al. 2013, p. 6〕 Few medicanes form during the summer season, though activity typically rises in autumn, peaks in January, and gradually decreases from February to May.〔 In the western Mediterranean region of development, approximately 0.75 such systems form each year, compared to 0.32 in the Ionian Sea region.〔Cavicchia et al. 2013, p. 8〕 Studies have evaluated that global warming can result in higher observed intensities of tropical cyclones as a result of deviations in the surface energy flux and atmospheric composition, which both heavily influence the development of medicanes as well. In tropical and subtropical areas, sea surface temperatures (SSTs) rose 0.2 °C (0.36 °F) within a 50-year period, and in the North Atlantic and Western Pacific tropical cyclone basins, the potential destructiveness and energy of storms nearly doubled within the same duration, evidencing a clear correlation between global warming and tropical cyclone intensities.〔Tous & Romero 2013, p. 9〕 Within a similarly recent 20-year period,〔Tous & Romero 2013, p. 10〕 SSTs in the Mediterranean Sea increased by 0.6 to 1 °C (1.08 to 1.8 °F),〔 though no observable increase in medicane activity has been noted as of August 2013.〔 In 2006, a computer-driven atmospheric model evaluated the future frequency of Mediterranean cyclones between 2071 and 2100, projecting a decrease in autumn, winter, and spring cyclonic activity coinciding with a dramatic increase in formation near Cyprus, with both scenarios attributed to elevated temperatures as a result of global warming.〔Anagnostopoulou et al. 2006, p. 13〕 Other studies, however, have been inconclusive, forecasting both increases and decreases in duration, number, and intensity.〔Gaertner et al. 2007, p. 4〕 Three independent studies, using different methodologies and data, evaluated that while medicane activity would likely decline with a rate depending on the climate scenario considered, a higher percentage of those that formed would be of greater strength.〔Cavicchia et al 2014, p. 7493〕〔Romero & Emanuel 2013, p. 6000〕〔Walsh et al 2014, p. 1059〕 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Mediterranean tropical-like cyclone」の詳細全文を読む スポンサード リンク
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