題目：北半球中高緯度極端熱浪事件頻率變化的機製分析

報告摘要：

近年來，北半球夏季極端熱浪事件頻發。中高緯度地區是高強度-長持續時間復合型極端熱浪事件高頻發生的關鍵區域🛝。1980年來，北半球中高緯度的高強度-長持續時間復合型極端熱浪事件的頻率顯著增加🎹。本研究通過對熱浪事件天氣尺度物理過程的分析，找出了觸發和維持該類極端熱浪事件的關鍵天氣系統和環境要素🧜🏿‍♀️。並進一步分析了大氣環流模態和土壤濕度等動力和熱力學因素的改變，如何通過影響事件期間地表的太陽輻射和陸氣相互作用，同時影響熱浪事件的強度和持續時間。分析結果表明，更強和維持時間更長的高壓系統，以及更低的背景土壤濕度是導致1980年以來北半球中高緯度高強度-長持續時間復合型極端熱浪事件頻率快速增多的主要動力和熱力學因素。

個人簡介🍜：王雨晴，沐鸣2博士後。2023年博士畢業於中國科學院南海海洋研究所。研究興趣🏄🏻‍♀️：極端天氣事件、海氣相互作用、大氣動力學等。

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

報告摘要：

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.

個人簡介：李朔，沐鸣2博士後。2023年5月博士畢業於北卡羅萊納大學教堂山分校🥑。2023年8月進入沐鸣2平台從事博士後研究工作🧯。研究興趣：熱帶氣旋，氣候動力學🤸🏻‍♀️，熱帶海氣相互作用🙊，大氣海洋數值模擬等💗。