Jan-Victor Björkqvist

• PhD
• PostDoc Position at Norwegian Meteorological Institute

Small lightweight wave buoys, SFYs, designed to operate near the coast, have been developed. The buoys are designed to record and transmit the full time series of surface acceleration at 52 Hz. The buoy uses the cellular network to transfer data and position (up to 80 km from the base station). This reduces costs and increases band-width. The low c...

This study presents an automatic algorithm for estimating the wind speed and direction from wave observations. The method rests upon the decades old field-validated theory that the energy of a certain part of the wave field is directly proportional to the wind speed. The wind properties were estimated using data from a small wave buoy moored in the...

Typical statistics, such as mean or percentiles, provide an excellent baseline for studying variations and changes in physical variables that have socioeconomic relevance. Nonetheless, they lack information on how often, and for how long, a certain wave height is exceeded, which might be needed for practical applications, such as planning marine op...

Small lightweight wave buoys, SFYs, designed to operate near the coast, have been developed. The buoys are designed to record and transmit the full time series of surface acceleration at 52 Hz. The buoy uses the cellular network to transfer data and position (up to 80 km from the base station). This reduces costs and increases band-width. The low c...

Typical statistics, such as mean or percentiles, provide an excellent baseline for studying variations and changes in physical variables that have socioeconomic relevance. Nonetheless, they lack information on how often, and for how long, a certain wave height is exceeded, which might be needed for practical applications, such as planning marine op...

DNORA is an open-source Python package for dynamical downscaling of the Norwegian wave hindcast (NORA3), global reanalysis ERA5 and regional forecasts (WAM4, WW3_4km) using different ocean wave models.

A better understanding of wave homogeneity, i.e. the spatial variations of the wave characteristics, and wave coherence in coastal areas and fjords is essential for the design and analysis of sea-crossing infrastructures, such as floating bridge concepts. The wave conditions in fjords that are exposed to the open sea are complex and often character...

As atmospheric models move to higher resolution and resolve smaller scales, the maximum modeled wind speed also tends to increase. Wave models tuned to coarser wind fields tend to overestimate the wave growth under strong winds. A recently developed semiempirical parameterization of the Charnock parameter, which controls the roughness length over s...

As atmospheric models move to higher resolution and resolve smaller scales, the maximum modeled wind speed also tends to increase. Wave models tuned to coarser wind fields tend to overestimate the wave growth under strong winds. A recently developed semi-empirical parameterization of the Charnock parameter, which controls the roughness length over...

Wave buoys are a popular choice for measuring sea surface waves, and there is also an increasing interest for wave information from ice-covered water bodies. Such measurements require cost-effective, easily deployable, and robust devices. We have developed LainePoiss (LP)—an ice-resistant and lightweight wave buoy. It calculates the surface elevati...

Both sea level variations and wind-generated waves affect coastal flooding risks. The correlation of these two phenomena complicates the estimates of their joint effect on the exceedance levels for the continuous water mass. In the northern Baltic Sea the seasonal occurrence of sea ice further influences the situation. We analysed this correlation...

The classic characterisation of swell as regular, almost monochromatic, wave trains does not necessarily accurately describe swell in water bodies shielded from the oceanic wave climate. In such enclosed areas the locally generated swell waves still contribute to processes at the air and seabed interfaces, and their presence can be quantified by pa...

A large part of oil spills happen near busy marine fairways. Presently, oil spill detection and monitoring are mostly done with satellite remote sensing algorithms, or with remote sensors or visual surveillance from aerial vehicles or ships. These techniques have their drawbacks and limitations. We evaluated the feasibility of using fluorometric se...

This study investigates the effect of surface currents on wind-generated waves in a complex coastal system with narrow fjords. The simulations are based on a phase-averaged wave model forced with surface currents from a high-resolution coastal ocean and fjord circulation model, and high-resolution winds from a nested atmospheric model. Wave simulat...

Swell dominates the global sea state and therefore significantly contributes to processes at the air and seabed interfaces. Nonetheless, smaller enclosed seas are detached from the global swell climate. We present swell statistics for the Baltic Sea using 20 years of swell partitioned model data. The swell significant wave height was mostly under 2...

Wave buoys are a popular choice for measuring sea surface waves, and there is also an increasing interest for wave information from ice-covered water bodies. Such measurements require cost-effective, easily deployable, and robust devices. We have developed LainePoiss (LP)-an ice-resistant and lightweight wave buoy. It calculates the surface elevati...

Currents in the Baltic Sea are generally weak, but during strong winds they can grow high enough to affect the surface wave propagation and evolution. To evaluate the significance of wave-current interactions in the Baltic Sea, we conducted a study using the wave model WAM, comparing a run without surface currents to one with current forcing from a...

Both sea level variations and wind-generated waves affect coastal flooding risks. The correlation of these two phenomena complicates the estimates of their joint effect on the exceedance levels for the continuous water mass. In the northern Baltic Sea the seasonal occurrence of sea ice further influences the situation. We analysed this correlation...

This paper presents how to account for the lack of sampling variability in model data when they are combined with wave measurements. We addressed the dissimilarities between the types of data by either (i) low-pass filtering the observations or (ii) adding synthetic sampling variability to the model. Measurement–model times series combined with the...

This paper investigates the performance of three different wave model source term packages in narrow fetch geometries. The packages are used to model the sea state in a complex coastal system with narrow fjords on the west coast of Norway. The modelling system is based on the Simulating WAves Nearshore (SWAN) wave model that is forced with winds fr...

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 t...

This paper presents how to account for the lack of sampling variability in model data when they are combined with wave measurements. We addressed the dissimilarities between the types of data by either: i) low-pass filtering the observations or ii) adding synthetic sampling variability to the model. Measurement–model times series combined with thes...

Abstract. 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...

Waves are important for both the leisure and safety of the human population. Open-sea waves have been studied since the 1940’s and their central properties are known. The wave field is described by the so called wave spectrum, which is a decomposition of the wave energy with respect to the wave frequency. In practice, the wave field is still often...

Sea surface waves are important for marine safety and coastal engineering, but mapping the wave properties at complex shorelines, such as coastal archipelagos, is challenging. The wave spectrum, E(f), contains a majority of the information about the wave field, and its properties have been studied for decades. Nevertheless, any systematic research...

The rear face of the wave spectrum is described by an equilibrium and a saturation subrange. Although accurate information about these ranges are highly relevant for wave modeling and many practical applications, there have been inconsistencies between results originating from temporal and spatial measurements. These discrepancies have been explain...

The seasonal ice cover has significant effect on the wave climate of the Baltic Sea. We used the third-generation wave model WAM to simulate the Baltic Sea wave field during four ice seasons (2009–2012). We used data from two different sources: daily ice charts compiled by FMI's Ice Service and modeled daily mean ice concentration from SMHI's NEMO-...

WAM, SWAN and WAVEWATCH III ® were implemented to the Finnish archipelago with a 0.1 nmi grid. A comparison with coastal wave buoy observations showed that the models agreed on the significant wave height, with biases and root-mean-square-errors (RMSE) differing at most 0.06 m. In a general sense, WAM propagated most long wave energy into the archi...

Sea surface waves are important for marine safety and coastal constructions, but mapping the wave properties at complex shorelines, such as coastal archipelagos, is challenging. The wave spectrum, E(f), contains a majority of the information about the wave field, and its properties have been studied for decades. Nevertheless, any systematic researc...

The general objective of EXWE was to give better estimates of probabilities of extreme geophysical events that affect the design principles of nuclear power plants (NPPs) and may pose external threats to the plants. Extreme incidents in weather, sea level events and space weather, as well as atmospheric dispersion were considered. Various observati...

In this study, a third-generation wave model is used to examine the wave power resource for the Baltic Sea region at an unprecedented one-kilometer-scale resolution for the years 1998 to 2013. Special focus is given to the evaluation and description of wave field characteristics for the Swedish Exclusive Economic Zone (SEEZ). It is carried out to p...

Tools for estimating probabilities of flooding hazards caused by the simultaneous effect of sea level and waves are needed for the secure planning of densely populated coastal areas that are strongly vulnerable to climate change. In this paper we present a method for combining location-specific probability distributions of three different component...

Tools for estimating probabilities of flooding hazards caused by the simultaneous effect of sea level and waves are needed for the secure planning of densely populated coastal areas that are strongly vulnerable to climate change. In this paper we present a method for combining location-specific probability distributions of three different component...

The Stokes drift is an important component in the surface drift. We used the wave model WAM to evaluate the mean values and exceedance probabilities of the surface Stokes drift in the Baltic Sea. As there is no direct way to verify the accuracy of the modelled Stokes drift, we compared the bulk parameters calculated by the wave model against buoy m...

A significant wave height of 7 m has been measured five times by the northern Baltic Proper wave buoy in the Baltic Sea, exceeding 8 m twice (2004 and 2017). We classified these storms into two groups by duration and wave steepness. Interestingly, the two highest events exhibited opposite properties, with the 2017 event being the longest storm on r...

The seasonal ice cover in the Baltic Sea causes measurement gaps by forcing an early recovery of the instruments. We study the impact of these gaps on exceedance value estimates by restricting the model hindcast to only times that coincide with buoy measurements. The comparison reveals that including the time not captured by the wave buoy can affec...

We present ice-free and ice-included statistics for the Baltic Sea using a wave hindcast validated against data from 13 wave measurement sites. In the hindcast 84% of wave events with a significant wave height over 7 m occurred between November and January. The effect of the ice cover is largest in the Bay of Bothnia, where the mean significant wav...

Wave reflection at a steep shore radically affects the proper building height and must therefore be taken into account in coastal planning. The reflection of the waves can be partially mitigated by building e.g. wave damping chambers. While there is a great deal of laboratory data available even for irregular waves, field data verifying the effecti...

In order to more fully understand the specific hydrodynamic relationship between young, wind-generated gravity-capillary waves and longer gravity waves, a laboratory experiment was devised to observe changes in short wave spectral behavior over the phase of a long wave. This study endeavors to expand on the body of laboratory wave modulation data a...

The heterogeneous coastline of the Gulf of Finland can result in widely varying wave conditions in a small geographical area. It is therefore challenging to obtain comprehensive information about the wave spectrum, which is needed to accurately quantify, e.g. the wave-bottom interactions. In this study, we implemented the wave model WAM to the coas...

In this study we describe a previously unreported error in the vertical displacement time series made with GPS-based Datawell DWR-G4 wave buoys and introduce a simple method to correct the resulting wave spectra. The artefact in the time series is found to resemble a sawtooth wave, which produces an erroneous trend following an f−2 power law in fre...

The coastal area off Helsinki in the Gulf of Finland has both a complex shoreline and bathymetry which makes modelling the wave field especially challenging. Experience has shown, that these types of areas generally benefits from the use of a high-resolution model grid. Even though the coastal area is very sensitive to the resolution, this is not n...

The Archipelago Sea, located between the Baltic Proper and the Gulf of Bothnia, has countless small islands. The southern edge of the Archipelago Sea is also characterized with shoals that cause wave refraction and depth-induced wave breaking. To assist safe and efficient shipping in this area wave forecasts, with resolution high enough to solve th...

The Archipelago Sea, located in the Baltic Sea between the Gulf of Bothnia and the Baltic Proper, comprises thousands of small islands and shoals. The sheltering effects, depth-induced wave breaking and refraction make the modelling of waves challenging in this area. Ten different high-resolution grids were generated based on coastal nautical chart...

The coastal areas of Finland are covered with islands and shoals of variable sizes. The total amount of islands is over 73 000. Ca. 40 000 of the islands are located in the south-western extremity of Finland in the Archipelago Sea. The size of the islands varies from a few meters to several kilometres in diameter. The bathymetry is complex; there a...