南印度洋热带气旋快速增强事件气候特征及其年际变率

利用美国联合台风预警中心的热带气旋最佳路径数据集、美国国家海洋和大气管理局的扩展重构海表温度数据、全球海洋数据同化系统的温度、盐度数据及美国国家环境预报中心/国家大气研究中心的再分析资料, 分析了1981—2019年南印度洋热带气旋快速增强事件的气候特征和年际变率。结果表明, 南印度洋热带气旋快速增强事件产生频率呈现单峰分布, 主要产生在每年的12月至次年4月。南印度洋热带气旋增强事件的产生位置呈带状分布, 其中3个高值中心分别位于马达加斯加岛东北海域、南印度洋中部海域和澳大利亚西北海域, 这主要是由于热带气旋热潜和垂直风切变两个大尺度环境变量决定的。年际变率方面, 厄尔尼诺-南方涛动对南印度洋热带气旋增强事件产生频率的调制作用是不对称的, 厄尔尼诺年与拉尼娜年南印度洋热带气旋快速增强事件均减少, 但使其减少的物理机制不同。厄尔尼诺年, 热带气旋快速增强事件减少主要是较高的垂直风切变造成的; 拉尼娜年, 热带气旋快速增强事件减少主要是由于热带气旋热潜的降低, 而海表温度、垂直风切变和相对湿度也存在一定贡献。

Climatic characteristics and interannual variability of tropical cyclone rapid intensification in the South Indian Ocean

Using tropical cyclone (TC) data from the Joint Typhoon Warning Center, the Extended Reconstructed Sea Surface Temperature version 5 from the National Oceanic and Atmospheric Administration, the temperature and salinity data from the Global Ocean Data Assimilation System, and the reanalysis data from the National Centers for Environmental Prediction/National Center for Atmospheric Research, we investigated climatic characteristics and interannual variability of TC rapid intensification (RI) in the South Indian Ocean (SIO) during the period of 1981~2019. The occurrence frequency of RI events in the SIO presents a single peak distribution, which ranges from October to June of the next year. The occurrence of SIO RI events is distributed in the subtropical area in a belt shape, with three high-value centers of RI events located in the northeast of Madagascar, the middle of the SIO and the northwest of Australia. The spatial distribution of SIO RI events is mainly modulated by two large-scale environmental variables: tropical cyclone heat potential (TCHP) and vertical wind shear (VWS). We also found that the influence of El Niño-Southern Oscillation on the occurrence frequency of SIO RI events is asymmetric: the occurrence frequencies of RI events during El Niño and La Niña years are both reduced. During El Niño years, the decrease of RI events is mainly due to higher VWS. During La Niña years, the decrease of RI events is mainly due to lower TCHP, and SST; VWS and RHUM also contribute to the decrease of RI events.