题目：北半球中高纬度极端热浪事件频率变化的机制分析

报告摘要：

近年来，北半球夏季极端热浪事件频发。中高纬度地区是高强度-长持续时间复合型极端热浪事件高频发生的关键区域。1980年来，北半球中高纬度的高强度-长持续时间复合型极端热浪事件的频率显著增加。本研究通过对热浪事件天气尺度物理过程的分析，找出了触发和维持该类极端热浪事件的关键天气系统和环境要素。并进一步分析了大气环流模态和土壤湿度等动力和热力学因素的改变，如何通过影响事件期间地表的太阳辐射和陆气相互作用，同时影响热浪事件的强度和持续时间。分析结果表明，更强和维持时间更长的高压系统，以及更低的背景土壤湿度是导致1980年以来北半球中高纬度高强度-长持续时间复合型极端热浪事件频率快速增多的主要动力和热力学因素。

个人简介：王雨晴，复旦大学大气与海洋科学系博士后。2023年博士毕业于中国科学院南海海洋研究所。研究兴趣：极端天气事件、海气相互作用、大气动力学等。

题目：The variability and predictability of tropical cyclone genesis frequency in the North Atlantic and Northwest Pacific

报告摘要：

The variability and predictability of tropical cyclone genesis frequency (TCGF) in the North Atlantic and Northwest Pacific are studied using a 100-member ensemble of climate simulations by a 60-km atmospheric general circulation model that is forced with observed sea surface temperatures (SSTs). The ensemble-mean results well capture the interannual-to-decadal variability of hurricane frequency in best track data since 1970 in the North Atlantic. A genesis potential index averaged over the main development region accounts for more than 80% of the SST-forced variations in hurricane frequency, with potential intensity and vertical wind shear being the dominant factors. The hurricane frequency also exhibits strong internal variability, and in practice, a 20-member ensemble is sufficient to capture the SST-forced variability. We further investigated the TCGF at both basin-wide and sub-basin scales in the Northwest Pacific. The sub-basin regions include the South China Sea (SCS) and the four quadrants of the open ocean. The ensemble-mean results well reproduce the observed year-to-year variability of TCGF in the southeast (SE), northeast (NE) and northwest (NW) quadrants, but show limited skill in the SCS and southwest (SW) quadrant. Both empirical and theoretical analyses suggest that ensembles of ~10, 20, 35 and 15 members can capture the SST-forced TCGF variability in the SE, NE and NW quadrants and the entire basin, respectively. In the SW quadrant and SCS, TCGF contains excessive noise, particularly in the observations, and thus shows low predictability.

个人简介：李朔，复旦大学大气与海洋科学系博士后。2023年5月博士毕业于北卡罗莱纳大学教堂山分校。2023年8月进入复旦大学从事博士后研究工作。研究兴趣：热带气旋，气候动力学，热带海气相互作用，大气海洋数值模拟等。