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Explosive cyclogenesis (also referred to as a weather bomb, meteorological bomb, explosive development,〔 or bombogenesis〔(【引用サイトリンク】url=http://www.wbrz.com/videos/ryan-explains-bomb-cyclogenesis/ )〕) refers in a strict sense to a rapidly deepening extratropical cyclonic low-pressure area. To enter this category, the central pressure of a depression at 60˚ latitude is required to decrease by 24 mb (hPa) or more in 24 hours. This is a predominantly maritime, cold-season (winter) event,〔 but also occurs in continental settings. They are the extra-tropical equivalent of the tropical rapid deepening. ==History== In the 1940s and 50s meteorologists at the Bergen School of Meteorology began informally calling some storms that grew over the sea "bombs" because they developed with a ferocity rarely, if ever, seen over land. By the 1970s the terms "explosive cyclogenesis" and even "meteorological bombs" were being used by MIT professor Fred Sanders (building on work from the 1950s by Tor Bergeron), who brought the term into common usage in a 1980 article in the Monthly Weather Review.〔〔 In 1980, Sanders and his colleague John Gyakum defined a "bomb" as an extratropical cyclone that deepens by at least (24 sin φ/ sin 60˚)mb in 24 hours, where φ represents latitude in degrees. This is based on the definition, standardised by Bergeron, for explosive development of a cyclone at 60˚N as deepening by 24mb in 24 hours. Sanders and Gyakum noted that an equivalent intensification is dependent on latitude: at the poles this would be a drop in pressure of 28 mb/24 hours, while at 25 degrees latitude it would be only 12 mb/24 hours. All these rates qualify for what Sanders and Gyakum called "1 bergeron".〔〔 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「Explosive cyclogenesis」の詳細全文を読む スポンサード リンク
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