Meteotsunamis in the northern Baltic Sea and their relation to synoptic patterns

Pellikka, Havu; Šepić, Jadranka; Lehtonen, Ilari; Vilibić, Ivica (2022) Meteotsunamis in the northern Baltic Sea and their relation to synoptic patterns. Weather and Climate Extremes, 38 . ISSN 22120947

PDF - Published Version - article Available under License Creative Commons Attribution Non-commercial No Derivatives. Download (20MB)

Abstract

Low-tidal coastal regions, such as the Baltic Sea, are known to be particularly vulnerable to exceptional high-frequency sea level oscillations such as meteotsunamis. Possibilities of studying sub-hourly sea level variations have recently improved, owing to advancement in temporal resolution of tide gauge observations. In this work, we study high-frequency (period <6 h) sea level oscillations – strongest of which we consider to be meteotsunamis – on the coast of Finland, in the northern Baltic Sea, using quality-checked 1-min observations collected between 2004 and 2015 at 13 tide gauge stations. The intensity of the oscillations varies substantially between stations due to local coastal morphologies. The most intense oscillations predominantly occur in late summer and autumn, although the seasonality may differ between sub-regions. Measured atmospheric data and reanalysis products related to the strongest events reveal two distinct types of atmospheric processes and governing synoptic patterns that are mostly associated with warmer and colder period of year. Consequently, meteotsunamis are classified as summer-type or winter-type events. Most of the summer-type events are caused by surface atmospheric pressure jumps associated with mesoscale convective systems, which are advancing northward over the sea and are embedded into a mid-troposphere jet overtopping an inflow of warm low-troposphere air. At the surface, weak air pressure gradients due to a high-pressure area to the east and a low-pressure area to the west of the Baltic are usually found during summer-type events. The winter-type events, on the contrary, are mostly related to cold fronts and strong northerly-northwesterly-westerly winds at the surface layer. Contrary to summer-type events, surface atmospheric pressure jumps are not necessarily detected during the strongest winter-type events. Deep lows and extratropical cyclones are commonly centered to the north of the Baltic Sea and, at the mid-troposphere level, there is a pronounced westerly jet stream. A hypothesis about the generation mechanism of intense high-frequency sea level oscillations is given: Proudman resonance appears to be the main driver of summer-type events, whereas the main driver of winter-type events is less clear.

Item Type:	Article
Uncontrolled Keywords:	sea level variations; sea level extremes; Baltic Sea; meteotsunami; high-frequency sea level oscillations
Subjects:	NATURAL SCIENCES > Geophysics
Divisions:	Division for Marine and Enviromental Research
Projects:	Project title Project leader Project code Project type Procjena doprinosa oscilacija razine mora perioda kraćeg od jednog sata ukupnim ekstremima razine mora u promjenjivim klimatskim uvjetima Jadranka Šepić 853045 Znanstveno-istraživački projekti Snaga i varijabilnost ekstremnih razina Jadranskog mora u sadašnjoj i budućoj klimi Jadranka Šepić IP-2019-04-5875 Znanstveno-istraživački projekti
Depositing User:	Lorena Palameta
Date Deposited:	27 Nov 2023 14:13
URI:	http://fulir.irb.hr/id/eprint/8229
DOI:	10.1016/j.wace.2022.100527

Actions (login required)

View Item