关键词: 中国, 热带气旋, 厄尔尼诺年, 拉尼娜年, 统计预报模式

Abstract:

China witnesses serious disasters of tropical cyclones every year. There were 459 tropical cyclones landing along the coast of China in 1951-2000, of which 15 tropical cyclones are in the maximum year, 4 tropical cyclones in the minimum year, and 9.2 tropical cyclones in the average year. According to the relationship analysis between tropical cyclones landing in China and El Nino years and La Nina years, some results are obtained as follows: (1) There are less frequencies of tropical cyclones landing in China in El Nino years; (2) the greater the intensity of El Nino event, the less the frequencies of tropical cyclones landing in China; (3) if the finish time of El Nino event appears after May 1, there are less frequencies of tropical cyclones landing in China in the following year; (4) the years of extremely high frequencies of tropical cyclones landing in China are mainly in La Nina years; (5) there are less frequencies of tropical cyclones landing in China in the following year of La Nina years; (6) the greater the intensity of tropical cyclones landing in China, the less the arising possibility in El Nino years; and (7) there are later tropical cyclones first-landing in China, and earlier tropical cyclones last-landing in China in El Nino years. The knowledge can be regarded as the formula of statistical forecast of frequencies of tropical cyclones landing in China, which is of the forecasting significance. It is demonstrated by analysis that there is the comparatively close relationship between tropical cyclones landing in China and sea surface temperature in the Pacific. In fact El Nino and La Nina events are one of the main physical factors affecting tropical cyclones landing in China via the sea-air function. Rising and maintaining of tropical cyclones needs the huge energy, and ocean surface of high temperature is its huge energy warehouse. When El Nino event appears, the energy supply decreases in the main source area of tropical cyclones, the inter-tropical convergence zone becomes weaker, and the activity of cumulus convection is affected because sea surface temperature in the tropical western Pacific reduces. Therefore there is an environmental field that tropical cyclones disadvantageously rise and develop. In this way there are less tropical cyclones landing in China. When La Nina event appears, there is quite the opposite situation.

Key words: China, tropical cyclones, El Nino year, La Nina year, formula of statistical forecast