摘要
El Nino衰减年西北太平洋热带气旋(Tropical cyclone,TC)活动表现出多样性,给TC活动的气候预测带来挑战。采用美国联合台风预警中心的热带气旋最佳路径数据和欧洲中期预报中心提供的ERA-5再分析资料,对1970—2018年的El Nino衰减年7—10月的西北太平洋TC生成频数进行合成分析,发现其与气候态没有显著的差异,但在单个年份,存在着较大的正、负异常。为此,将El Nino衰减年分为TC生成频数偏少(负异常)和偏多(正异常)两种情形,对比两种情形的TC活动和大尺度环境要素特征。结果表明,TC生成频数偏少的情形,TC生成频数的异常减少主要发生在西北太平洋东部海域,即(15°~25°N,140°~150°E)和(5°~25°N,150°~170°E),与垂直风切变增大、对流层中层相对湿度和低层绝对涡度减少有关;TC生成频数偏多的情形,TC生成频数的异常增加主要发生在南海和菲律宾群岛附近,即(15°~25°N,110°~120°E)和(5°~25°N,120°~130°E),对流层中层相对湿度增加的贡献最大,其次是上升运动增强和绝对涡度增大;对比两种情形发现,TC生成频数偏多的情形,广东和福建沿岸的东南风异常引导气流有利于菲律宾群岛附近生成的TC登陆中国大陆。
In the El Nino decaying years,the activities of Tropical Cyclone(TC)over the Northwest Pacific show diversity,which bring challenges to the climate prediction of TC activities.In this paper,the characteristics of TC activities over the Northwest Pacific were analyzed from 1970 to 2018(from July to October)by using TC track data derived from the JTWC and ERA-5 reanalysis data provided by the ECMWF.No significant anomalies can be seen from the TC genesis frequency over the whole Northwest Pacific,but there are huge positive and negative anomalies in a single year.Therefore,according to TC genesis frequency,El Nino decaying years were divided into two conditions:less TC(negative anomalies)and more TC(positive anomalies),and the characteristics of large-scale environmental variables in the two cases are compared.Results show that in the case of less TC,the TC genesis frequency was seen abnormally reduced,which mainly occurred in the eastern region of Northwest Pacific(15°-25°N,140°-150°E and 5°-25°N,150°-170°E).The phenomena were related to the reduction of relative humidity in the middle troposphere,the increasing in vertical wind shear and the decreasing in low-level absolute vorticity.In the case of more TC,the anomalous increase of TC genesis frequency mainly occurred near the South China Sea and the Philippine Islands(15°-25°N,110°-120°E and 5°-25°N,120°-130°E).The contribution of increasing of relative humidity the middle troposphere was the largest,followed by the increasing in relative vorticity and ascending motion.By comparing the two scenarios,it is found that in the case of more TC,the anomalous of Southeast guide wind along the coast of Guangdong and Fujian is favorable for the TC generation near the Philippines Islands to land in China's Mainland.
作者
钟校尧
余锦华
欧立健
张旭煜
ZHONG Xiaoyao;YU Jinhua;OU Lijian;ZHANG Xuyu(School of Atmospheric Science,Nanjing University of Information Science&Technology,Nanjing 210044,China)
出处
《气象科学》
北大核心
2022年第2期204-212,共9页
Journal of the Meteorological Sciences
基金
国家重点研发计划项目(2018YFC1507700)
国家自然科学基金资助项目(41730961,41575083)。
