scholarly journals Classification and properties of coastal wind profiles with negative gradients – an observational study

2022 ◽  
Author(s):  
Christoffer Hallgren ◽  
Johan Arnqvist ◽  
Erik Nilsson ◽  
Stefan Ivanell ◽  
Metodija Shapkalijevski ◽  
...  
Keyword(s):  
Baltic Sea ◽  
Local Minimum ◽  
Stable Stratification ◽  
Offshore Wind ◽  
The Baltic Sea ◽  
Wind Maximum ◽  
Low Level ◽  
Low Level Jets ◽  
Wind Profiles ◽  
The Baltic

Abstract. Wind profiles with a negative gradient are frequently occurring over the Baltic Sea and are important to take into consideration for offshore wind power as they affect not only the power production, but also the loads on the structure and the behavior of the wake behind the turbine. In this study, we classified non-normal profiles as wind profiles having negative shear in at least one part of the profile between 28 and 300 m: low-level jets (with a local wind maximum in the profile), profiles with a local minimum, and negative profiles. Using observations spanning over 3 years, we show that the non-normal wind profiles are common over the Baltic Sea in late spring and summer, with a peak of 40 % relative occurrence in May. Negative profiles (in the 28–300 m layer) were mostly occurring during unstable conditions, in contrast to low-level jets that primarily occurred in stable stratification. There were indications that the the zone with strong shear during low-level jets could cause a relative suppression of the variance for large turbulent eddies compared to the peak of the velocity spectra, in the layer below the jet core. Swell conditions were found to be favourable for the occurrence of negative profiles and profiles with a local minimum, as the waves fed energy into the surface layer, resulting in an increase of the wind speed from below.

scholarly journals Looking for an Offshore Low-Level Jet Champion among Recent Reanalyses: A Tight Race over the Baltic Sea

Energies ◽  
2020 ◽  
Vol 13 (14) ◽  
pp. 3670
Author(s):  
Christoffer Hallgren ◽  
Johan Arnqvist ◽  
Stefan Ivanell ◽  
Heiner Körnich ◽  
Ville Vakkari ◽  
...  
Keyword(s):  
Baltic Sea ◽  
Wind Farms ◽  
Resource Assessment ◽  
Offshore Wind ◽  
The Baltic Sea ◽  
Average Wind Speed ◽  
Low Level ◽  
Wide Range ◽  
Low Level Jets ◽  
The Baltic

With an increasing interest in offshore wind energy, focus has been directed towards large semi-enclosed basins such as the Baltic Sea as potential sites to set up wind turbines. The meteorology of this inland sea in particular is strongly affected by the surrounding land, creating mesoscale conditions that are important to take into consideration when planning for new wind farms. This paper presents a comparison between data from four state-of-the-art reanalyses (MERRA2, ERA5, UERRA, NEWA) and observations from LiDAR. The comparison is made for four sites in the Baltic Sea with wind profiles up to 300 m. The findings provide insight into the accuracy of reanalyses for wind resource assessment. In general, the reanalyses underestimate the average wind speed. The average shear is too low in NEWA, while ERA5 and UERRA predominantly overestimate the shear. MERRA2 suffers from insufficient vertical resolution, which limits its usefulness in evaluating the wind profile. It is also shown that low-level jets, a very frequent mesoscale phenomenon in the Baltic Sea during late spring, can appear in a wide range of wind speeds. The observed frequency of low-level jets is best captured by UERRA. In terms of general wind characteristics, ERA5, UERRA, and NEWA are similar, and the best choice depends on the application.

Wind conditions over the Baltic Sea – comparing reanalysis data sets with observations

2020 ◽  
Author(s):  
Christoffer Hallgren ◽  
Erik Sahlée ◽  
Stefan Ivanell ◽  
Heiner Körnich ◽  
Ville Vakkari
Keyword(s):  
Baltic Sea ◽  
Wind Power ◽  
Reanalysis Data ◽  
Data Sets ◽  
The Baltic Sea ◽  
Data Set ◽  
Low Level ◽  
Seasonal And Diurnal Variations ◽  
Low Level Jets ◽  
The Baltic

<p>The potential of increasing the amount of offshore wind energy production in the Baltic Sea has been of great interest for many countries and wind power companies for a long time. From a meteorological point of view, there are several special wind characteristics that are observed in this area that needs to be taken into consideration when planning for a wind farm. For example, as the Baltic Sea is a semi-enclosed basin surrounded by coastlines in all directions, phenomenon such as low-level jets occur frequently.</p><p>In order to create a climatology of the wind conditions over the Baltic Sea, with wind power applications in mind, four different state-of-the-art reanalysis data sets (MERRA2, ERA5, UERRA and NEWA) have been compared with measurements from LIDAR systems and high meteorological towers (Anholt, Finnish Utö, FINO2 and Östergarnsholm). The performance of the data sets has been analyzed in terms of stability and governing synoptic weather conditions as well as seasonal and diurnal variations. By selecting the most suitable reanalysis data set and using the observations to make corrections, a climatology for wind conditions over the Baltic Sea, focusing on the low-level jets, has then been constructed.</p>

scholarly journals A sensitivity study of the WRF model in offshore wind modeling over the Baltic Sea

2021 ◽  
pp. 101229
Author(s):  
Huidong Li ◽  
Björn Claremar ◽  
Lichuan Wu ◽  
Christoffer Hallgren ◽  
Heiner Körnich ◽  
...  
Keyword(s):  
Baltic Sea ◽  
Wrf Model ◽  
Sensitivity Study ◽  
Offshore Wind ◽  
The Baltic Sea ◽  
Wind Modeling ◽  
The Baltic

scholarly journals Bacteriohopanepolyols record stratification, nitrogen fixation and other biogeochemical perturbations in Holocene sediments of the central Baltic Sea

2013 ◽  
Vol 10 (4) ◽  
pp. 2725-2735 ◽  
Author(s):  
M. Blumenberg ◽  
C. Berndmeyer ◽  
M. Moros ◽  
M. Muschalla ◽  
O. Schmale ◽  
...  
Keyword(s):  
Baltic Sea ◽  
Water Column ◽  
Stable Stratification ◽  
The Baltic Sea ◽  
Allochthonous Input ◽  
The North ◽  
Water Column Stratification ◽  
Gotland Deep ◽  
History Of ◽  
The Baltic

Abstract. The Baltic Sea, one of the world's largest brackish-marine basins, established after deglaciation of Scandinavia about 17 000 to 15 000 yr ago. In the changeable history of the Baltic Sea, the initial freshwater system was connected to the North Sea about 8000 yr ago and the modern brackish-marine setting (Littorina Sea) was established. Today, a relatively stable stratification has developed in the water column of the deep basins due to salinity differences. Stratification is only occasionally interrupted by mixing events, and it controls nutrient availability and growth of specifically adapted microorganisms and algae. We studied bacteriohopanepolyols (BHPs), lipids of specific bacterial groups, in a sediment core from the central Baltic Sea (Gotland Deep) and found considerable differences between the distinct stages of the Baltic Sea's history. Some individual BHP structures indicate contributions from as yet unknown redoxcline-specific bacteria (bacteriohopanetetrol isomer), methanotrophic bacteria (35-aminobacteriohopanetetrol), cyanobacteria (bacteriohopanetetrol cyclitol ether isomer) and from soil bacteria (adenosylhopane) through allochthonous input after the Littorina transgression, whereas the origin of other BHPs in the core has still to be identified. Notably high BHP abundances were observed in the deposits of the brackish-marine Littorina phase, particularly in laminated sediment layers. Because these sediments record periods of stable water column stratification, bacteria specifically adapted to these conditions may account for the high portions of BHPs. An additional and/or accompanying source may be nitrogen-fixing (cyano)bacteria, which is indicated by a positive correlation of BHP abundances with Corg and δ15N.

scholarly journals Baltic Offshore Wind Energy Development—Poland’s Public Policy Tools Analysis and the Geostrategic Implications

Energies ◽  
2021 ◽  
Vol 14 (16) ◽  
pp. 4883
Author(s):  
Kamila Pronińska ◽  
Krzysztof Księżopolski
Keyword(s):  
Public Policy ◽  
Wind Energy ◽  
Baltic Sea ◽  
Wind Power ◽  
Offshore Wind ◽  
Policy Tools ◽  
Offshore Wind Energy ◽  
The Baltic Sea ◽  
Offshore Wind Power ◽  
The Baltic

A key question for European energy transition is which forms of renewable energy technologies will play a central role in this process. The recent dynamic growth in offshore wind power together with the vast wind energy potential of the European seas, including the Baltic Sea, make this technology an increasingly attractive and viable option. Considering the high installation and connection costs, government support is considered essential for the development of offshore wind power. The aim of this article is to analyze Poland’s public policy tools, which govern offshore wind farm development, and to present them from a wider geostrategic perspective. Authors identify, classify, and evaluate individual public policy tools with the use of multi-criteria and multi-dimensional methods while explaining their impact on offshore wind development in Poland. The analysis of the individual tools has shown that the currently applied tools give a high probability of achieving public policy objectives. The characteristics of the applied tools prove that vital decisions on offshore wind energy have been made concerning the need for decarbonization but also regarding wider geostrategic calculations. Given the changing security dynamics in the Baltic Sea region, we highlight potential geostrategic risks to the implementation of offshore wind projects.

scholarly journals Estimates of the aerosol indirect effect over the Baltic Sea region derived from 12 years of MODIS observations

2017 ◽  
Vol 17 (4) ◽  
pp. 3133-3143 ◽  
Author(s):  
Giulia Saponaro ◽  
Pekka Kolmonen ◽  
Larisa Sogacheva ◽  
Edith Rodriguez ◽  
Timo Virtanen ◽  
...  
Keyword(s):  
Baltic Sea ◽  
Eastern Europe ◽  
Cloud Fraction ◽  
Effective Radius ◽  
The Baltic Sea ◽  
Low Level ◽  
Central Eastern Europe ◽  
Cloud Properties ◽  
Baltic Sea Region ◽  
The Baltic

Abstract. Retrieved from the Moderate Resolution Imaging Spectroradiometer (MODIS) on-board the Aqua satellite, 12 years (2003–2014) of aerosol and cloud properties were used to statistically quantify aerosol–cloud interaction (ACI) over the Baltic Sea region, including the relatively clean Fennoscandia and the more polluted central–eastern Europe. These areas allowed us to study the effects of different aerosol types and concentrations on macro- and microphysical properties of clouds: cloud effective radius (CER), cloud fraction (CF), cloud optical thickness (COT), cloud liquid water path (LWP) and cloud-top height (CTH). Aerosol properties used are aerosol optical depth (AOD), Ångström exponent (AE) and aerosol index (AI). The study was limited to low-level water clouds in the summer. The vertical distributions of the relationships between cloud properties and aerosols show an effect of aerosols on low-level water clouds. CF, COT, LWP and CTH tend to increase with aerosol loading, indicating changes in the cloud structure, while the effective radius of cloud droplets decreases. The ACI is larger at relatively low cloud-top levels, between 900 and 700 hPa. Most of the studied cloud variables were unaffected by the lower-tropospheric stability (LTS), except for the cloud fraction. The spatial distribution of aerosol and cloud parameters and ACI, here defined as the change in CER as a function of aerosol concentration for a fixed LWP, shows positive and statistically significant ACI over the Baltic Sea and Fennoscandia, with the former having the largest values. Small negative ACI values are observed in central–eastern Europe, suggesting that large aerosol concentrations saturate the ACI.

Sign in / Sign up

Export Citation Format

Share Document