Abstract. We analyse changes in meteotsunami occurrence over the past century (1922–2014) in the Gulf of Finland, Baltic Sea. A major challenge for studying these short-lived and local events is the limited temporal and spatial resolution of digital sea level and meteorological data. To overcome this challenge, we examine archived paper recordings from two tide gauges, Hanko for 1922–1989 and Hamina for 1928–1989, from the summer months of May–October. We visually inspect the recordings to detect rapid sea level variations, which are then digitised and compared to air pressure observations from nearby stations. The data set is complemented with events detected from digital sea level data 1990–2014 by an automated algorithm. In total, we identify 121 potential meteotsunami events. Over 70 % of the events could be confirmed to have a rapid change in air pressure occurring shortly before or simultaneously with the sea level oscillations. The occurrence of meteotsunamis is strongly connected with lightning over the region: the number of cloud-to-ground (CG) flashes over the Gulf of Finland were on average over 10 times higher during the days when a meteotsunami was recorded compared to days with no meteotsunamis in May–October. On a monthly level, statistically significant differences between meteotsunami months and other months were found in the number of CG flashes, convective available potential energy (CAPE), and temperature. Meteotsunami occurrence over the past century shows a statistically significant increasing trend in Hamina, but not in Hanko.

中文翻译：

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过去一个世纪芬兰湾的 Meteotsunami 发生

摘要。我们分析了过去一个世纪（1922-2014 年）芬兰湾、波罗的海的气象海啸发生的变化。研究这些短期和局部事件的一个主要挑战是数字海平面和气象数据的有限时间和空间分辨率。为了克服这一挑战，我们检查了 5 月至 10 月夏季月份的两个潮汐测量仪的存档纸质记录，1922-1989 年的 Hanko 和 1928-1989 年的 Hamina。我们目视检查记录以检测海平面的快速变化，然后将其数字化并与附近站点的气压观测值进行比较。该数据集补充了通过自动算法从 1990-2014 年数字海平面数据中检测到的事件。我们总共确定了 121 个潜在的气象海啸事件。可以确认超过 70% 的事件在海平面振荡之前不久或同时发生了气压的快速变化。气象海啸的发生与该地区的闪电密切相关：在记录到气象海啸的日子里，芬兰湾上空的云对地 (CG) 闪光次数比没有记录的日子平均高出 10 倍以上。 5 月至 10 月的气象海啸。在每月水平上，meteotsunami 月份和其他月份之间在 CG 闪光次数、对流可用势能 (CAPE) 和温度方面存在统计学上的显着差异。过去一个世纪的 Meteotsunami 发生在 Hamina 显示出统计上显着的增加趋势，但在 Hanko 没有。