入境宁波的热带气旋活动特征的气候统计及其年代际变化

Characteristics of Tropical Cyclone Landfall in Ningbo: Climatological Statistics and Decadal Variability

本文利用中国气象局热带气旋(TC)资料中心最佳路径数据集,对入境宁波的TC进行统计,从1949到2014年共有71个TC入境宁波,通过合成分析和显著性检验发现:TC源地强东风引导气流的存在和西风带的南北位置是影响TC路径的重要原因。在1990s中后期以来的全球变暖减缓阶段,入境宁波的TC频数在9~10月份显著增多。1990s中后期之后,整个太平洋海表面温度(SST)呈现出太平洋年代际涛动(PDO)的负位相和赤道太平洋的类拉尼娜型海温分布,Walker环流增强,调制了西太副高的加强和西伸,使得西北太平洋TC移动路径偏西,登陆我国海岸线中段的TC频数增多,造成了在9~10月份入境宁波的TC频数增多。就TC生成而言,1990s年代中期之后西北太平洋TC源地西部垂直风切变的减弱和相对湿度的增加可能造成了TC生成的增加,而较东位置则与之相反。

Based on the Best Track Dataset from China Meteorological Administration during 1949-2014, there were 71 tropical cyclones (TCs) during the period landfall in Ningbo. According to composited analysis and t-test, the area which TC genesis with strong east-wind and the location of westerlies play an important role in TC moving. During the autumn season (September and October) of global warming hiatus epoch after the mid-to-end of 1990s, the TC number of moving to Ningbo was increased significantly. The reason may be associated with the Pacific decadal oscillation became into its negative phase. Since the sea surface temperature showing a La Nina-like pattern, which enhanced Walker Circulation and further modulated western Pacific subtropical high (WPSH), the WPSH extended westward and intensified, causing TC moving favorite to western region and favorite landing at Chinese mainland. The genesis of TC over the western North Pacific also appears interdecadal shift indicated by genesis potential index of TC. The decreasing of vertical wind shear and increasing of relative humidity play a dominant role in TC genesis increasing.