| 1. |
- Rutgersson, Anna, 1971-, et al.
(författare)
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Natural hazards and extreme events in the Baltic Sea region
- 2022
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Ingår i: Earth System Dynamics. - : Copernicus Publications. - 2190-4979 .- 2190-4987. ; 13:1, s. 251-301
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Tidskriftsartikel (refereegranskat)abstract
- A natural hazard is a naturally occurring extreme event that has a negative effect on people and society or the environment. Natural hazards may have severe implications for human life and can potentially generate economic losses and damage ecosystems. A better understanding of their major causes, probability of occurrence, and consequences enables society to be better prepared to save human lives as well as to invest in adaptation options. Natural hazards related to climate change are identified as one of the Grand Challenges in the Baltic Sea region. Here, we summarize existing knowledge about extreme events in the Baltic Sea region with a focus on the past 200 years as well as on future climate scenarios. The events considered here are the major hydro-meteorological events in the region and include wind storms, extreme waves, high and low sea levels, ice ridging, heavy precipitation, sea-effect snowfall, river floods, heat waves, ice seasons, and drought. We also address some ecological extremes and the implications of extreme events for society (phytoplankton blooms, forest fires, coastal flooding, offshore infrastructure, and shipping). Significant knowledge gaps are identified, including the response of large-scale atmospheric circulation to climate change and also concerning specific events, for example, the occurrence of marine heat waves and small-scale variability in precipitation. Suggestions for future research include the further development of high-resolution Earth system models and the potential use of methodologies for data analysis (statistical methods and machine learning). With respect to the expected impacts of climate change, changes are expected for sea level, extreme precipitation, heat waves and phytoplankton blooms (increase), and cold spells and severe ice winters (decrease). For some extremes (drying, river flooding, and extreme waves), the change depends on the area and time period studied.
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| 2. |
- Osterwalder, S., et al.
(författare)
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Critical Observations of Gaseous Elemental Mercury Air-Sea Exchange
- 2021
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Ingår i: Global Biogeochemical Cycles. - : American Geophysical Union (AGU). - 0886-6236 .- 1944-9224. ; 35:8
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Tidskriftsartikel (refereegranskat)abstract
- Air-sea exchange of gaseous elemental mercury (Hg-0) is not well constrained, even though it is a major component of the global Hg cycle. Lack of Hg-0 flux measurements to validate parameterizations of the Hg-0 transfer velocity contributes to this uncertainty. We measured the Hg-0 flux on the Baltic Sea coast using micrometeorological methods (gradient-based and relaxed eddy accumulation [REA]) and also simulated the flux with a gas exchange model. The coastal waters were typically supersaturated with Hg-0 (mean +/- 1 sigma = 13.5 +/- 3.5 ng m(-3); ca. 10% of total Hg) compared to the atmosphere (1.3 +/- 0.2 ng m(-3)). The Hg-0 flux calculated using the gas exchange model ranged from 0.1-1.3 ng m(-2) h(-1) (10th and 90th percentile) over the course of the campaign (May 10-June 20, 2017) and showed a distinct diel fluctuation. The mean coastal Hg-0 fluxes determined with the two gradient-based approaches and REA were 0.3, 0.5, and 0.6 ng m(-2) h(-1), respectively. In contrast, the mean open sea Hg-0 flux measured with REA was larger (6.3 ng m(-2) h(-1)). The open sea Hg-0 flux indicated a stronger wind speed dependence for the Hg-0 transfer velocity compared to commonly used parameterizations. Although based on a limited data set, we suggest that the wind speed dependence of the Hg-0 transfer velocity is more consistent with gases that have less water solubility than CO2 (e.g., O-2). These pioneering flux measurements using micrometeorological techniques show that more such measurements would improve our understanding of air-sea Hg exchange.
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| 3. |
- Guo Larsén, Xiaoli, et al.
(författare)
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Climate Change and Offshore Wind Energy in the Baltic Sea
- 2024
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Ingår i: Oxford Research Encyclopedia of Climate Science.
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Forskningsöversikt (refereegranskat)abstract
- Wind energy is becoming an essential part of the energy system in the Baltic Sea region (BSR). There has been a tremendous development of offshore wind energy in the early 21st century in this region, and the plan for further growth in the coming years is ambitious. The development and implementation of offshore wind energy is a complex process involving many physical and sociopolitical aspects. These aspects have their own characteristics in the BSR. Therefore, they have their unique impact and constraints on the regional development and implementation of the strategic energy technology (SET) plans. This includes implementing next-generation wind turbine technology, offshore wind farms and system integration, floating offshore wind and wind energy industrialization, wind energy operation, maintenance and installation, ecosystems, social impact and human capital agendas, and basic wind energy sciences.Climate change is an important issue to address in relation to future development. Among the questions that may arise are: How would climate change affect the wind resource, extreme wind, and several meteorological and oceanic variables relevant to the offshore wind energy sector? What does this effect imply for the development of offshore wind energy in the BSR?It is encouraging to acknowledge that there have been numerous relevant, good quality, pertinent studies on the subject of the BSR, and many more are ongoing. It is also inspiring to see that in the wind energy sector, there are already many technologies, methods, and tools that are sufficiently mature, and many of them, together with lessons learned through studies in other offshore regions, can be applied to support the urgent and extensive scale development of offshore wind in the BSR.
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| 4. |
- Wu, Lichuan, et al.
(författare)
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A review of surface swell waves and their role in air-sea interactions
- 2024
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Ingår i: Ocean Modelling. - : Elsevier. - 1463-5003 .- 1463-5011. ; 190
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Forskningsöversikt (refereegranskat)abstract
- Swell waves, characterized by the long wavelength components generated by distant weather systems or storms, exert a significant influence on various air-sea interaction processes, thereby impacting weather and climate systems. Over recent decades, substantial progress has been achieved in comprehending the dynamics of swell waves and their implications for air-sea interactions. This paper presents a comprehensive review of advancements and key findings concerning surface swell waves and their interactions with the atmosphere. It encompasses a range of topics, including wave growth theory, the effects of swell waves on air-sea momentum, heat, and mass fluxes, as well as their influence on atmospheric turbulence and mixed layer processes. The most important characteristics of the swell impact (where it differs from wind sea conditions) are the wave-induced upward component of the surface stress leading to alteration of total surface stress, generation of a low-level wind maxima or changed wind profile and change of scale and behaviour of turbulence properties (turbulence kinetic energy and integral length scale). Furthermore, the paper explores the modelling of swell dissipation, the integration of swell influences in weather and climate models, and the broader climatic implications of surface swell waves. Despite notable advances in understanding swell processes, persistent knowledge gaps remain, underscoring the need for further research efforts, which are outlined in the paper.
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| 5. |
- Molinder, Jennie, et al.
(författare)
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Probabilistic Forecasting of Wind Turbine Icing Related Production Losses Using Quantile Regression Forests
- 2021
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Ingår i: Energies. - BASEL, SWITZERLAND : MDPI. - 1996-1073. ; 14:1
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Tidskriftsartikel (refereegranskat)abstract
- A probabilistic machine learning method is applied to icing related production loss forecasts for wind energy in cold climates. The employed method, called quantile regression forests, is based on the random forest regression algorithm. Based on the performed tests on data from four Swedish wind parks available for two winter seasons, it has been shown to produce valuable probabilistic forecasts. Even with the limited amount of training and test data that were used in the study, the estimated forecast uncertainty adds more value to the forecast when compared to a deterministic forecast and a previously published probabilistic forecast method. It is also shown that the output from a physical icing model provides useful information to the machine learning method, as its usage results in an increased forecast skill when compared to only using Numerical Weather Prediction data. A potential additional benefit in machine learning for some stations was also found when using information in the training from other stations that are also affected by icing. This increases the amount of data, which is otherwise a challenge when developing forecasting methods for wind energy in cold climates.
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| 6. |
- Gutiérrez Loza, Lucia, et al.
(författare)
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On physical mechanisms enhancing air-sea CO2 exchange
- 2022
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Ingår i: Biogeosciences. - : European Geosciences Union (EGU). - 1726-4170 .- 1726-4189. ; 19:24, s. 5645-5665
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Tidskriftsartikel (refereegranskat)abstract
- Reducing uncertainties in the air–sea CO2 flux calculations is one of the major challenges when addressing the oceanic contribution in the global carbon balance. In traditional models, the air–sea CO2 flux is estimated using expressions of the gas transfer velocity as a function of wind speed. However, other mechanisms affecting the variability in the flux at local and regional scales are still poorly understood. The uncertainties associated with the flux estimates become particularly large in heterogeneous environments such as coastal and marginal seas. Here, we investigated the air–sea CO2 exchange at a coastal site in the central Baltic Sea using nine years of eddy covariance measurements. Based on these observations we were able to capture the temporal variability of the air–sea CO2 flux and other parameters relevant for the gas exchange. Our results show that a wind-based model with similar pattern to those developed for larger basins and open sea condition can, on average, be a good approximation for k. However, in order to reduce the uncertainty associated to these averages and produce reliable short-term k estimates, additional physical processes must be considered. Using a normalized gas transfer velocity, we identified conditions associated to enhanced exchange (large k values). During high and intermediate wind speeds (above 6–8 m s−1),conditions on both sides of the air–water interface were found to be relevant for the gas exchange. Our findings further suggest that at such relatively high wind speeds, sea spray is an efficient mechanisms for air–sea CO2 exchange. During low wind speeds (<6 m s−1), water-side convection was found to be a relevant control mechanism. The effect of both sea spray and water-side convection on the gas exchange showed a clear seasonality with positive fluxes (winter conditions) being the most affected.
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| 7. |
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| 8. |
- Nilsson, Erik Olof, 1983-
(författare)
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Fluxes and Mixing Processes in the Marine Atmospheric Boundary Layer
- 2013
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Atmospheric models are strongly dependent on the turbulent exchange of momentum, sensible heat and moisture (latent heat) at the surface. Oceans cover about 70% of the Earth’s surface and understanding the processes that control air-sea exchange is of great importance in order to predict weather and climate. In the atmosphere, for instance, hurricane development, cyclone intensity and track depend on these processes.Ocean waves constitute an obvious example of air-sea interaction and can cause the air-flow over sea to depend on surface conditions in uniquely different ways compared to boundary layers over land. When waves are generated by wind they are called wind sea or growing sea, and when they leave their generation area or propagate faster than the generating wind they are called swell. The air-sea exchange is mediated by turbulent eddies occurring on many different scales. Field measurements and high-resolution turbulence resolving numerical simulations have here been used to study these processes.The standard method to measure turbulent fluxes is the eddy covariance method. A spatial separation is often used between instruments when measuring scalar flux; this causes an error which was investigated for the first time over sea. The error is typically smaller over ocean than over land, possibly indicating changes in turbulence structure over sea.Established and extended analysis methods to determine the dominant scales of momentum transfer was used to interpret how reduced drag and sometimes net upward momentum flux can persist in the boundary layer indirectly affected by swell. A changed turbulence structure with increased turbulence length scales and more effective mixing was found for swell.A study, using a coupled wave-atmosphere regional climate model, gave a first indication on what impact wave mixing have on atmosphere and wave parameters. Near surface wind speed and wind gradients was affected especially for shallow boundary layers, which typically increased in height from the introduced wave-mixing. A large impact may be expected in regions of the world with predominant swell. The impact of swell waves on air-sea exchange and mixing should be taken into account to develop more reliable coupled Earth system models.
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| 9. |
- Mahrt, Larry, et al.
(författare)
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The sea surface heat flux at a coastal site
- 2022
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Ingår i: Journal of Physical Oceanography. - : American Meteorological Society. - 0022-3670 .- 1520-0485. ; 52:12, s. 3297-3307
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Tidskriftsartikel (refereegranskat)abstract
- We analyze approximately four years of heat-flux measurements at two levels, profiles of air temperature, and multiple measurements of the water temperature collected at a coastal zone site. Our analysis considers underestimation of the sea-surface flux due to vertical divergence of the heat flux between the surface and the lowest flux level. We examine simple relationships of the heat flux to the wind speed and stratification and the potential influence of fetch and temperature advection. The fetch ranges from about 4 km to near 400 km. For a given wind-direction sector, the transfer coefficient varies only slowly with increasing instability, but decreases significantly with increasing stability. The intention here is not to recommend a new parameterization but rather to establish relationships that underly the bulk formula that could lead to assessments of uncertainty and improvement of the bulk formula.
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| 10. |
- Nilsson, Erik, 1983-, et al.
(författare)
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Assessment of Extreme and Metocean Conditions in the Swedish Exclusive Economic Zone for Wave Energy
- 2020
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Ingår i: Atmosphere. - : MDPI AG. - 2073-4433. ; 11:3
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Tidskriftsartikel (refereegranskat)abstract
- Here, accessibility to near-shore and offshore marine sites is evaluated based on wave and ice conditions. High-resolution third-generation wave model results are used to examine the operation and maintenance conditions for renewable energy sources with a focus on wave energy. Special focus is given to the wave field and ice characteristics for areas within the Swedish Exclusive Economic Zone including analysis of return levels for extreme values for significant wave height, which provides guidance for dimensioning wave energy converters. It is shown that the number of weather windows and accessibility are influenced by distance from the coast and sea-ice conditions. The longest waiting periods for the closest weather window that is available for Operation and Maintenance (O&M) is in ice-free conditions shown to be strongly correlated with the fetch conditions. The sheltered Baltic Sea is shown to have very high accessibility if marine infrastructure and vessels are designed for access limits of significant wave height up to 3 m. In the northern basins, the waiting periods increase significantly, if and when the ice-conditions are found to be critical for the O&M activity considered. The ice-conditions are examined based on compiled operational sea-ice data over a climatic time period of 34 years. The results are location specific for the Swedish Exclusive Economic Zone, but the analysis methods are transferable and applicable to many other parts of the world, to facilitate assessment of the most promising areas in different regions.
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