Locally calibrated wave hindcasts in the Estonian coastal sea in 1966–2011

Ü Suursaar

doi:10.3176/earth.2013.05

Abstract

Wave parameters were studied in four differently exposed fetch-limited Estonian coastal sea locations: the Harilaid Peninsula facing W-NW, Letipea N-NE, Matsi SW and Koiguste SE. Based on high-quality measurements of waves with the bottom-mounted Recording Doppler Current Profiler in 2006-2011, a model for significant wave height was calibrated separately for those locations. Using wind forcing data from Estonian coastal meteorological stations, a set of hindcasts was obtained over the period of 1966-2011. The wave heights showed some quasi-periodic cycles with a high stage in 1980-1995, and probably also from 2007; a prevailing overall decrease in the mean wave height; an increase in high wave events at the windward coasts of West Estonia but a decrease at the northern and southeastern coasts. The spatially contrasting results for differently exposed coasts reflect the corresponding variations in local wind, which are probably caused by changes in large-scale atmospheric pressure patterns above Northern Europe and a poleward shift of cyclones' trajectories. Although featuring outstanding calibration results, the long-term wave hindcast may be impacted by possible inhomogeneities in the older wind data.

Highlights

Data on surface waves and their long-term regimes – wave climates – are increasingly needed both in environmental investigations and engineering applications
Using wind forcing data from Estonian coastal meteorological stations, a set of hindcasts was obtained over the period of 1966–2011
The Estonian coastal sea is covered in a few Baltic Sea hindcasts (Jönsson et al 2002; Tuomi et al 2011)

Summary

Introduction

Data on surface waves and their long-term regimes – wave climates – are increasingly needed both in environmental investigations and engineering applications. According to numerous studies (Jaagus et al 2008; Suursaar & Kullas 2009; Keevallik 2011; Lehmann et al 2011), the wind climate above the Baltic Sea has experienced some seasonally contrasting and important changes over the last 50–100 years. These changes should be somehow reflected in the wave climate. Several modelling studies have addressed the wave climate in the northeastern (NE) section of the Baltic Sea and in the Estonian coastal sea in the last ten years. Depending on the data source and analysis method, these studies use three principally different approaches, each having its strengths and limitations

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