西北太平洋热带气旋频数的气候变化及其与环境要素间的联系

使用Emanuel和Nolan完善的潜在生成指数(GPI)的计算方法,利用美国联合台风警报中心提供的热带气旋(TC)资料和欧洲中期数值天气预报中心提供的全球ERA-40再分析资料,比较了1970-2001年西北太平洋海域的TC生成频数和GPI的气候特征,分析了包含于GPI中的环境要素对西北太平洋TC频数年代际变化空间分布的影响.结果表明:GPI能近似地表述西北太平洋TC频数的季节变化和空间分布.各环境要素对TC、较弱类TC和较强类TC生成频数的影响有显著差异,相对湿度随着TC强度的增强而减弱,风速垂直切变则相反.西北太平洋TC频数年代际变化空间分布的正异常主要分布于130°E以东,(15°N,140°E)附近最大的正异常频数中心主要受绝对涡度和相对湿度正异常变化的影响；负的风速垂直切变和正的相对湿度异常变化引起了(10～15°N,160°E)附近的TC频数正异常.

The climate change of tropical cyclone frequency and its relationship with environment factors in the western North Pacific

Based on the tropical cyclone(TC)data from Joint Typhoon Warning Center and the monthly reanalysis data provided by the European Center for Medium-range Weather Forecasts, the TC genesis frequency and climatology of GPI in the western North Pacific(WNP) during the period of 1970-2001 were compared and the influence of TC frequency of the spatial distribution interannual changes by the environment factors included in the GPI was analyzed with a calculation of genesis potential index(GPI)developed by Emanuel and Nolan. The results show that GPI could describe approximately the seasonal changes and spatial distribution of the TC frequency in the WNP. Impact environmental factors have on the TC, and weaker and stronger the TC frequency has significant difference. The stronger the TC intensity is, the weaker relative humidity is, while the vertical wind shear is opposite. The positive anomaly of the spatial distribution of interannual changes of the TC frequentcy in the WNP appears primarily in the area of east 130 °E.The largest of the positive anomaly of TC frequencies center near(15 °N,140 °E) is affected by the positive anomaly of the absolute vorticity and relative humidity.The abnomal variation of the negative vertical wind shear and positive relative humidity leads to TC frequencies positive anomaly near (10-15 °N,160 °E).