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- Claremar, Björn, 1980-, et al.
(author)
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Ship Emissions and the use of current air cleaning technology : contributions to air pollution and acidification in the Baltic Sea
- 2017
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In: Earth System Dynamics. - : Copernicus GmbH. - 2190-4979 .- 2190-4987. ; 8, s. 901-919
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Journal article (peer-reviewed)abstract
- The shipping sector is a significant contributor to emissions of air pollutants in marine and coastal regions.In order to achieve sustainable shipping, primarily through new regulations and techniques, greater knowledgeof dispersion and deposition of air pollutants is required. Regional model calculations of the dispersion andconcentration of sulfur, nitrogen, and particulate matter, as well as deposition of oxidized sulfur and nitrogenfrom the international maritime sector in the Baltic Sea and the North Sea, have been made for the years 2011to 2013. The contribution from shipping is highest along shipping lanes and near large ports for concentrationand dry deposition. Sulfur is the most important pollutant coupled to shipping. The contribution of both SO2concentration and dry deposition of sulfur represented up to 80% of the total in some regions. WHO guidelinesfor annual concentrations were not trespassed for any analysed pollutant, other than PM2:5 in the Netherlands,Belgium, and central Poland. However, due to the resolution of the numerical model, 50 km50 km, there maybe higher concentrations locally close to intense shipping lanes.Wet deposition is more spread and less sensitiveto model resolution. The contribution of wet deposition of sulfur and nitrogen from shipping was up to 30%of the total wet deposition. Comparison of simulated to measured concentration at two coastal stations close toshipping lanes showed some underestimations and missed maximums, probably due to resolution of the modeland underestimated ship emissions.A change in regulation for maximum sulfur content in maritime fuel, in 2015 from 1 to 0.1 %, decreasesthe atmospheric sulfur concentration and deposition significantly. However, due to costs related to refining, thecleaning of exhausts through scrubbers has become a possible economic solution. Open-loop scrubbers meet theair quality criteria but their consequences for the marine environment are largely unknown. The resulting potentialof future acidification in the Baltic Sea, both from atmospheric deposition and from scrubber water alongthe shipping lanes, based on different assumptions about sulfur content in fuel, scrubber usage, and increasedshipping density has been assessed. The increase in deposition for different shipping and scrubber scenariosdiffers for the basins in the Baltic Sea, with highest potential of acidification in the southern basins with hightraffic. The proportion of ocean-acidifying sulfur from ships increases when taking scrubber water into accountand the major reason for increasing acidifying nitrogen from ships is increasing ship traffic. Also, with the implementationof emission control for nitrogen, the effect of scrubbers on acidification is evident. This study alsogenerates a database of shipping and scrubber scenarios for atmospheric deposition and scrubber exhaust fromthe period 2011 to 2050.
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| 2. |
- Guseva, S., et al.
(author)
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Bulk Transfer Coefficients Estimated From Eddy-Covariance Measurements Over Lakes and Reservoirs
- 2023
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In: Journal of Geophysical Research - Atmospheres. - : American Geophysical Union (AGU). - 2169-897X .- 2169-8996. ; 128:2
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Journal article (peer-reviewed)abstract
- The drag coefficient, Stanton number and Dalton number are of particular importance for estimating the surface turbulent fluxes of momentum, heat and water vapor using bulk parameterization. Although these bulk transfer coefficients have been extensively studied over the past several decades in marine and large-lake environments, there are no studies analyzing their variability for smaller lakes. Here, we evaluated these coefficients through directly measured surface fluxes using the eddy-covariance technique over more than 30 lakes and reservoirs of different sizes and depths. Our analysis showed that the transfer coefficients (adjusted to neutral atmospheric stability) were generally within the range reported in previous studies for large lakes and oceans. All transfer coefficients exhibit a substantial increase at low wind speeds (<3 m s(-1)), which was found to be associated with the presence of gusts and capillary waves (except Dalton number). Stanton number was found to be on average a factor of 1.3 higher than Dalton number, likely affecting the Bowen ratio method. At high wind speeds, the transfer coefficients remained relatively constant at values of 1.6.10(-3), 1.4.10(-3), 1.0.10(-3), respectively. We found that the variability of the transfer coefficients among the lakes could be associated with lake surface area. In flux parameterizations at lake surfaces, it is recommended to consider variations in the drag coefficient and Stanton number due to wind gustiness and capillary wave roughness while Dalton number could be considered as constant at all wind speeds. Plain Language Summary In our study, we investigate the bulk transfer coefficients, which are of particular importance for estimation the turbulent fluxes of momentum, heat and water vapor in the atmospheric surface layer, above lakes and reservoirs. The incorrect representation of the surface fluxes above inland waters can potentially lead to errors in weather and climate prediction models. For the first time we made this synthesis using a compiled data set consisting of existing eddy-covariance flux measurements over 23 lakes and 8 reservoirs. Our results revealed substantial increase of the transfer coefficients at low wind speeds, which is often not taken into account in models. The observed increase in the drag coefficient (momentum transfer coefficient) and Stanton number (heat transfer coefficient) could be associated with the presence of wind gusts and capillary waves. In flux parameterizations at lake surface, it is recommended to consider them for accurate flux representation. Although the bulk transfer coefficients were relatively constant at high wind speeds, we found that the Stanton number systematically exceeds the Dalton number (water vapor transfer coefficient), despite the fact they are typically considered to be equal. This difference may affect the Bowen ratio method and result in biased estimates of lake evaporation.
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