近20 a影响我国台风活动变化趋势

利用最新定义的气旋活动指数CAI(Cyclone Activity Index)分析影响我国台风活动近20 a的变化趋势及其可能原因。分析发现,影响我国的台风频数自1996年以来显著减少,主要表现为南方沿海地区热带气旋影响减小,三亚和海口更呈显著下降的趋势(通过信度为0.05的统计检验),而东南方沿海地区热带气旋影响明显增加,厦门、福州、温州、杭州和上海夏季(6—10月)受到影响的程度显著上升(福州、温州和杭州通过信度为0.05的统计,上海和厦门通过信度为0.1的统计检验)。进一步分析表明,热带气旋活动的这些变化与台风盛行路径和强度的变化有密切关系。

Variation trend of typhoon activity influencing China during the past 20 years

Previous studies indicated that Tropical Cyclone (TC) intensity, frequency, locations of genesis and prevailing tracks over the western North Pacific might change under the background of global warming. Since TCs are one of the major natural disasters in China, the changes of TC activity may lead to significant loss of life and damage. In this study, the newly defined TC activity index Cyclone Activity Index (CAI) is used to examine the variations of TC influencing China''s coastal regions and its possible mechanisms. Results show that although no significant trend was seen in the landfall typhoon frequency over the past 50 years, a remarkable reduction was revealed in the frequency of typhoons affecting China after 1996. It is suggested that the southern (southeastern) coastal areas suffer from less (more) TC effects. The value of CAI increases in Xiamen, Fuzhou, Wenzhou, Hangzhou and Shanghai in summer (June-October) (the former three cities are significant at the 95% confidence level, while the latter two are significant at the 90% confidence test), on the contrary, a significant decreasing of CAI was presented in Sanya and Haikou (significant at the 95% confidence test). Further analysis indicates that these variations are closely associated with the changes in the TC prevailing tracks and intensity.