| 1. |
- Wen, Yuanqiao, et al.
(författare)
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Green routing design in short seas
- 2017
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Ingår i: International Journal of Shipping and Transport Logistics. - : INDERSCIENCE ENTERPRISES LTD. - 1756-6517 .- 1756-6525. ; 9:3, s. 371-390
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Tidskriftsartikel (refereegranskat)abstract
- In recent years, with the development of shipping industry, the mass of greenhouse gases (GHG) emissions originating from ships is also increasing rapidly. To reduce the GHG emissions from ships, designing the optimised routes with higher energy use efficiency is becoming more important for ships navigating in short seas. Based on the innovative application of energy efficiency operational index (EEOI), a route optimisation model is established. To solve the model, we divide one single voyage into several voyage segments and consider the variable speed across voyage segments. Then the navigation strategy is used to find out the sailing route of the minimum EEOI value, this sailing route is called as the green route. Finally, numerical experimental results show that the EEOI values of the experimental groups which used the optimised navigation method are 4.67%-16.95% lower than that of the control group. The results demonstrate that the green route designed in this paper can effectively improve the energy use efficiency of ships.
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| 2. |
- Cai, Yongqing, et al.
(författare)
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Factors Modulating the Variability of Eddy Kinetic Energy in the Southern Ocean from Idealized Simulations
- 2024
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Ingår i: Ocean-Land-Atmosphere Research. ; 3
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Tidskriftsartikel (refereegranskat)abstract
- The Southern Ocean is characterized by high levels of eddy activity, which are crucial for the vertical exchange or transfer of matter, energy, and momentum. Previous studies have shown that the variability of eddy kinetic energy (EKE) in the Southern Ocean is primarily intrinsic. However, the factors that modulate the forced and intrinsic variability of the EKE remain unclear. In this study, we conduct a series of idealized simulations and apply ensemble analysis to investigate the impact of topography and wind-stress perturbations on the forced and intrinsic variability of the EKE and their relative contributions. The results show that while the large wind-stress perturbation obviously increases the forced variability of EKE by enhancing the Ekman response, the topography not only amplifies the forced variability by sharpening isopycnals and energizing the mean flow but also intensifies the intrinsic variability of EKE. However, EKE variabilities in both complex-topographic and flat-bottom cases are dominated by their intrinsic components, even when driven by escalated wind-stress perturbations. These findings deepen our understanding of the eddy field, its ongoing variability in the Southern Ocean, and its potential impact on the balance of heat, carbon, and freshwater.
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| 3. |
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| 4. |
- Cai, Yongqing, et al.
(författare)
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Impact of wave breaking on upper-ocean turbulence
- 2017
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Ingår i: Journal of Geophysical Research - Oceans. - 2169-9275 .- 2169-9291. ; 122:2, s. 1513-1528
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Tidskriftsartikel (refereegranskat)abstract
- Previous studies have demonstrated that surface wave breaking can impact upper-ocean turbulence through wave-breaking-induced turbulence kinetic energy (TKE) flux and momentum flux. Wave-breaking-induced momentum flux decays approximately exponentially with depth, and the decay exponent depends on both the wind speed and wave age. With increasing wave age, the decay speed of wave-breaking-induced momentum flux first decreases, reaching a minimum around a wave age of 16, and then increases. In this study, a wave-breaking-induced momentum flux parameterization was proposed based on wave age and wind-speed dependence. The new proposed parameterization was introduced into a one-dimensional (1-D) ocean model along with a wave-age-dependent wave-breaking-induced TKE flux parameterization. The simulation results showed that the wave-breaking impact on the ocean mainly affected the upper-ocean layer. Adding the wave-age impact to the wave-breaking-induced TKE flux and momentum flux improved the 1-D model performance concerning the sea temperature. Moreover, the wave-breaking-induced momentum flux had a larger impact on the simulation results than the wave-breaking-induced TKE flux.
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| 5. |
- Emmanuel, George Victor, et al.
(författare)
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Role of source terms in parameterizing wave decay in the marginal ice zones
- 2022
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Ingår i: Ocean Modelling. - : Elsevier. - 1463-5003 .- 1463-5011. ; 180
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Tidskriftsartikel (refereegranskat)abstract
- Wave decay in the marginal ice zones (MIZ) plays a crucial role in shaping the Arctic Ocean behaviours. Parameterizing wave decay in the MIZ is indispensable in climate models for better capturing the climate change in the Arctic. However, current wave decay parameterizations were developed without considering the influences of wave source terms. This study investigated the role and contributions of different source terms in shaping the MIZ wave decay based on sensitivity simulations. Simulation results show that the ice-induced damping term is the main contributor to MIZ wave decay. The wind input source term also plays an important role in the wave evolution in the MIZ. During high wind speeds (wind speed>10 m/s), wind input was found to increase the wave height by about 10% on average (relative to the wave height decayed by ice), irrespective of the sea ice concentration. Wind input contributes up to 30% in high wind speed areas with low sea ice concentration. Meanwhile, the contributions from wind input term to MIZ wave are more important when winds blow from the open water to MIZ. However, the angle between winds and waves is insignificant in shaping contributions from wind input. Low SIC and high wind speed conditions also favour the enhancement of wave spreading. In general, the contributions from nonlinear wave–wave interactions and dissipation source terms were found to play a minor role in shaping MIZ wave decay. However, the role of nonlinear wave–wave interactions can be important in shaping the wave spectrum. Thus, it is suggested to update the model wave decay parameterizations to accommodate the role played by wind input source term, in particular under high wind speed conditions.
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| 6. |
- Gröger, Matthias, et al.
(författare)
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Coupled regional Earth system modeling in the Baltic Sea region
- 2021
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Ingår i: Earth System Dynamics. - : Copernicus GmbH. - 2190-4979 .- 2190-4987. ; 12:3, s. 939-973
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Forskningsöversikt (refereegranskat)abstract
- Nonlinear responses to externally forced climate change are known to dampen or amplify the local climate impact due to complex cross-compartmental feedback loops in the Earth system. These feedbacks are less well represented in the traditional stand-alone atmosphere and ocean models on which many of today's regional climate assessments rely (e.g., EURO-CORDEX, NOSCCA and BACC II). This has promoted the development of regional climate models for the Baltic Sea region by coupling different compartments of the Earth system into more comprehensive models. Coupled models more realistically represent feedback loops than the information imposed on the region by prescribed boundary conditions and, thus, permit more degrees of freedom. In the past, several coupled model systems have been developed for Europe and the Baltic Sea region. This article reviews recent progress on model systems that allow two-way communication between atmosphere and ocean models; models for the land surface, including the terrestrial biosphere; and wave models at the air-sea interface and hydrology models for water cycle closure. However, several processes that have mostly been realized by one-way coupling to date, such as marine biogeochemistry, nutrient cycling and atmospheric chemistry (e.g., aerosols), are not considered here. In contrast to uncoupled stand-alone models, coupled Earth system models can modify mean near-surface air temperatures locally by up to several degrees compared with their stand-alone atmospheric counterparts using prescribed surface boundary conditions. The representation of small-scale oceanic processes, such as vertical mixing and sea-ice dynamics, appears essential to accurately resolve the air-sea heat exchange over the Baltic Sea, and these parameters can only be provided by online coupled high-resolution ocean models. In addition, the coupling of wave models at the ocean-atmosphere interface allows for a more explicit formulation of small-scale to microphysical processes with local feedbacks to water temperature and large-scale processes such as oceanic upwelling. Over land, important climate feedbacks arise from dynamical terrestrial vegetation changes as well as the implementation of land-use scenarios and afforestation/deforestation that further alter surface albedo, roughness length and evapotranspiration. Furthermore, a good representation of surface temperatures and roughness length over open sea and land areas is critical for the representation of climatic extremes such as heavy precipitation, storms, or tropical nights (defined as nights where the daily minimum temperature does not fall below 20gC), and these parameters appear to be sensitive to coupling. For the present-day climate, many coupled atmosphere-ocean and atmosphere-land surface models have demonstrated the added value of single climate variables, in particular when low-quality boundary data were used in the respective stand-alone model. This makes coupled models a prospective tool for downscaling climate change scenarios from global climate models because these models often have large biases on the regional scale. However, the coupling of hydrology models to close the water cycle remains problematic, as the accuracy of precipitation provided by atmosphere models is, in most cases, insufficient to realistically simulate the runoff to the Baltic Sea without bias adjustments. Many regional stand-alone ocean and atmosphere models are tuned to suitably represent present-day climatologies rather than to accurately simulate climate change. Therefore, more research is required into how the regional climate sensitivity (e.g., the models' response to a given change in global mean temperature) is affected by coupling and how the spread is altered in multi-model and multi-scenario ensembles of coupled models compared with uncoupled ones.
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| 7. |
- Huang, Hongxun, et al.
(författare)
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Identification and detection of high NOx emitting inland ships using multi-source shore-based monitoring data
- 2024
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Ingår i: Environmental Research Letters. - : Institute of Physics Publishing (IOPP). - 1748-9326. ; 19:4
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Tidskriftsartikel (refereegranskat)abstract
- In urban areas situated along busy waterways like the Yangtze River, the diesel engines of inland navigation ships emerge as significant contributors to air pollution. Among these vessels, certain high-emission ships exhibit considerably higher levels of nitrogen oxides (NOx) emissions compared to others. To effectively identify such ships, this study employed a cost-effective ship emission monitoring sensor platform, comprising high-precision gas sensors, automatic identification system (AIS) receiver, and sensitive meteorological sensors, along the Yangtze River in Wuhan City. By combining multi-source shore-based monitoring data, we identified ship emission signals and proposed a high-emission ship detection method using inverse modelling. Using this method, we successfully detected inland high-emission ships based on two months of monitoring data. Furthermore, the relationship between different ship types, sizes, speeds, and ship NOx emission rates were investigated. The results of this study are beneficial for strengthening the regulation of high-emission vessels in inland waterways, thereby reducing the adverse impact of ship emissions on the environment and climate. It also encourages the inland shipping industry to adopt more environmentally friendly technologies and fuels, as advocated by the International Maritime Organization.
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| 8. |
- Jeworrek, Julia, et al.
(författare)
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Characteristics of convective snow bands along the Swedish east coast
- 2017
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Ingår i: Earth System Dynamics. - : Copernicus GmbH. - 2190-4979 .- 2190-4987. ; 8, s. 163-175
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Tidskriftsartikel (refereegranskat)abstract
- Convective snow bands develop in response to a cold air outbreak from the continent or the frozen sea over the open water surface of lakes or seas. The comparatively warm water body triggers shallow convection due to increased heat and moisture fluxes. Strong winds can align with this convection into wind-parallel cloud bands, which appear stationary as the wind direction remains consistent for the time period of the snow band event, delivering enduring snow precipitation at the approaching coast. The statistical analysis of a dataset from an 11-year high-resolution atmospheric regional climate model (RCA4) indicated 4 to 7 days a year of moderate to highly favourable conditions for the development of convective snow bands in the Baltic Sea region. The heaviest and most frequent lake effect snow was affecting the regions of Gavle and Vastervik (along the Swedish east coast) as well as Gdansk (along the Polish coast). However, the hourly precipitation rate is often higher in le than in the Vtervik region. Two case studies comparing five different RCA4 model setups have shown that the Rossby Centre atmospheric regional climate model RCA4 provides a superior representation of the sea surface with more accurate sea surface temperature (SST) values when coupled to the ice-ocean model NEMO as opposed to the forcing by the ERA-40 reanalysis data. The refinement of the resolution of the atmospheric model component leads, especially in the horizontal direction, to significant improvement in the representation of the mesoscale circulation process as well as the local precipitation rate and area by the model.
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| 9. |
- Li, Huidong, et al.
(författare)
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A sensitivity study of the WRF model in offshore wind modeling over the Baltic Sea
- 2021
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Ingår i: Geoscience Frontiers. - : Elsevier. - 1674-9871. ; 12:6
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Tidskriftsartikel (refereegranskat)abstract
- Accurate wind modeling is important for wind resources assessment and wind power forecasting. To improve the WRF model configuration for the offshore wind modeling over the Baltic Sea, this study performed a sensitivity study of the WRF model to multiple model configurations, including domain setup, grid resolution, sea surface temperature, land surface data, and atmosphere-wave coupling. The simulated offshore wind was evaluated against LiDAR observations under different wind directions, atmospheric stabilities, and sea status. Generally, the simulated wind profiles matched observations, despite systematic underestimations. Strengthening the forcing from the reanalysis data through reducing the number of nested domains played the largest role in improving wind modeling. Atmosphere-wave coupling further improved the simulated wind, especially under the growing and mature sea conditions. Increasing the vertical resolution, and updating the sea surface temperature and the land surface information only had a slight impact, mainly visible during very stable conditions. Increasing the horizontal resolution also only had a slight impact, most visible during unstable conditions. Our study can help to improve the wind resources assessment and wind power forecasting over the Baltic Sea.
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| 10. |
- Lin, Ting, et al.
(författare)
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Impact of sea spray-mediated heat fluxes on polar low development
- 2024
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Ingår i: Quarterly Journal of the Royal Meteorological Society. ; n/a:n/a
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Tidskriftsartikel (refereegranskat)abstract
- Abstract Sea spray, originating from wave breaking under high wind conditions, can significantly affect turbulent heat fluxes at the air–sea interface. Even though polar lows (PLs) can become extreme weather features with gale-force wind, the impact of sea spray on their development has rarely been investigated and is not considered in operational forecast models. In this study, the impact of sea spray on the development of two PLs over the Barents Sea is studied based on sensitivity experiments with an atmosphere–wave coupled model, where the spray-mediated heat fluxes are parameterized. The results show that the impact of sea-spray-mediated heat fluxes on PL development is sensitive to the surface wind speed. In the case of the stronger PL, the higher surface wind speed results in significantly higher spray-mediated heat fluxes. Consequently, these spray-mediated heat fluxes intensify the convection and diabatic heating of the PL, resulting in its intensification. In comparison, the case with a weaker PL experiences less sea spray production and lower spray-mediated heat fluxes due to its weaker surface wind speeds. Overall, we find that spray-mediated sensible heat fluxes play an important role in the development of PLs, while the latent heat fluxes induced by sea spray have a relatively minor impact.
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| 11. |
- Olsson, Taru, et al.
(författare)
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Statistics of sea-effect snowfall along the Finnish coastline based on regional climate model data
- 2020
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Ingår i: Advances in Science and Research. - : COPERNICUS GESELLSCHAFT MBH. - 1992-0628 .- 1992-0636. ; 17, s. 87-104
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Tidskriftsartikel (refereegranskat)abstract
- The formation of convective sea-effect snowfall (i.e., snow bands) is triggered by cold air outbreaks over a relatively warm and open sea. Snow bands can produce intense snowfall which can last for several days over the sea and potentially move towards the coast depending on wind direction. We defined the meteorological conditions which statistically favor the formation of snow bands over the north-eastern Baltic Sea of the Finnish coastline and investigated the spatio-temporal characteristics of these snow bands. A set of criteria, which have been previously shown to be able to detect the days favoring sea-effect snowfall for Swedish coastal area, were refined for Finland based on four case study simulations, utilizing a convection-permitting numerical weather prediction (NWP) model (HARMONIE-AROME). The main modification of the detection criteria concerned the threshold for 10 m wind speed: the generally assumed threshold value of 10 ms 1 was decreased to 7 ms(-1). The refined criteria were then applied to regional climate model (RCA4) data, for an 11-year time period (2000-2010). When only considering cases in Finland with onshore wind direction, we found on average 3 d yr(-1) with favorable conditions for coastal sea-effect snowfall. The heaviest convective snowfall events were detected most frequently over the southern coastline. Statistics of the favorable days indicated that the lower 10 m wind speed threshold improved the representation of the frequency of snow bands. For most of the favorable snow band days, the location and order of magnitude of precipitation were closely captured, when compared to gridded observational data for land areas and weather radar reflectivity images. Lightning were observed during one third of the favorable days over the Baltic Sea area.
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| 12. |
- Peng, Xin, et al.
(författare)
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A sampling method for calculating regional ship emission inventories
- 2020
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Ingår i: Transportation Research Part D. - : Elsevier BV. - 1361-9209 .- 1879-2340. ; 89
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Tidskriftsartikel (refereegranskat)abstract
- In this study, we propose a sampling method for calculating ship exhaust emission inventories, which reduces the uncertainties induced by missing ship static data in traditional methods. The stratified random sampling method is utilized to take sample ships based on the ship density, ship type, and main engine power. The exhaust emissions from sample ship are calculated using an activity-based method with 1Â s temporal resolution AIS (Automatic Identification System) data. Then the regional ship exhaust emissions are estimated based on the sampling relationship. Sensitivity experiments show that the relative error of the proposed method decreases quickly with the sampling ratio (the ratio between the number of sampled ships and total ships) and it is less than 3.5% when the sampling ratio is higher than 10%. The method is used to estimate the inventories of ship exhaust emissions in the Yangtze river, which can improve the computational accuracy of ship emissions.
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| 13. |
- Peng, Xin, et al.
(författare)
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Optimal site selection for the remote-monitoring sulfur content of ship fuels in ports
- 2022
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Ingår i: Ocean and Coastal Management. - : Elsevier. - 0964-5691 .- 1873-524X. ; 225
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Tidskriftsartikel (refereegranskat)abstract
- The remote monitoring method based on air-quality monitoring sensors is a common way to monitor the FSC (fuel sulfur content) of oils for ships. Considering the influences of geographical environments, atmospheric conditions, regional ship traffic flow, emission characteristics of ships, and height of monitoring sensors on the monitor station chosen, a new method was proposed to optimize the site selection for monitoring the FSC of fuel oils used by ships in waters of the port. SO2 numeric simulation and observation from sensors were integrated to estimate the FSCs. The proposed method was utilized to recommend the sites of the fixed sniffing monitoring stations in Yantian port, Shenzhen, China from June and July 2018. The results showed that the experimental stations could monitor FSCs, and the relative difference between the estimated and actual FSCs of ships was 16.34%. The proposed method for recommending sites of FSC monitoring sensors contributed to intelligently supervising air pollutants emitted from ships and fuel oils of ships in the emission control areas of China.
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| 14. |
- Peng, Xin, et al.
(författare)
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Remote detection sulfur content in fuel oil used by ships in emission control areas : A case study of the Yantian model in Shenzhen
- 2021
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Ingår i: Ocean Engineering. - : Elsevier. - 0029-8018 .- 1873-5258. ; 237
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Tidskriftsartikel (refereegranskat)abstract
- A method is proposed for remotely detecting sulfur content in fuel oil used by ships in emission control areas (ECAs) based on the direct collection of SO2 emission data from the plume of the ship and numerical simulation models. Assuming a ship in the ECA uses fuel oil with compliance fuel sulfur content (FSC), activity-based ship emission assessment model is firstly utilized to calculate the SO2 concentration emitted from the ship. Numerical simulation models are then used to estimate the theoretical SO2 diffusion concentration at the location of the monitoring equipment. The observed SO2 concentration at the same time can then be integrated to estimate the FSC of the ship. A sample of eleven ships was selected to verify the proposed method in Yantian port, Shenzhen, China in June 2018. The result illustrates that the method can remotely detect ships using fuel oil with the FSC greater than 0.146%m/m in the ECAs, the relative error is 46%.
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| 15. |
- Qiao, Wenli, et al.
(författare)
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Momentum Flux Balance at the Air-Sea Interface
- 2021
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Ingår i: Journal of Geophysical Research - Oceans. - : American Geophysical Union (AGU). - 2169-9275 .- 2169-9291. ; 126:2
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Tidskriftsartikel (refereegranskat)abstract
- Abstract Ocean waves can spatiotemporally redistribute the momentum flux at the air-sea interface, which varies with the sea state. Traditional atmosphere-ocean coupled systems assume the ocean-side stress (τoc) to be identical to the air-side stress (τa); consequently, the role of ocean waves is neglected. In this study, the wave impacts on the air-sea momentum flux are investigated based on 1-year high-resolution model simulations in the Baltic Sea using an atmosphere-wave coupled model (Uppsala University-Coupled Model, UU-CM). The simulation results show that τoc can differ significantly from τa in both direction and magnitude. The direction difference between τoc and τa (DD(τoc, τa)) and the normalized momentum flux () decrease with increasing inverse wave age. In general, and DD(τoc, τa) are pronounced under wind-following swell and wind-crossing swell conditions, respectively. The occurrence frequencies of large and DD(τoc, τa) are higher nearer the coast; statistically, both decrease significantly with increasing water depth because of the joint effect of dissipation processes. Based on four selected areas, we find that alongshore winds (winds blowing parallel to the coastline) are favorable for large angular differences between τoc and τa (DD(τoc, τa) > 5°). However, onshore winds predominate at . The τa in the wave model is generally less than that obtained from the atmospheric model under low-moderate wind conditions if the wave model feeds only the Charnock coefficient (roughness length) back to the atmospheric model in coupled systems.
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| 16. |
- Rutgersson, Anna, 1971-, et al.
(författare)
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Using land-based stations for air–sea interaction studies
- 2020
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Ingår i: Tellus. Series A, Dynamic meteorology and oceanography. - : Informa UK Limited. - 0280-6495 .- 1600-0870. ; 72:1, s. 1-23
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Tidskriftsartikel (refereegranskat)abstract
- In situ measurements representing the marine atmosphere and air-sea interaction are taken at ships, buoys, stationary moorings and land-based towers, where each observation platform has structural restrictions. Air-sea fluxes are often small, and due to the limitations of the sensors, several corrections are applied. Land-based towers are convenient for long-term observations, but one critical aspect is the representativeness of marine conditions. Hence, a careful analysis of the sites and the data is necessary. Based on the concept of flux footprint, we suggest defining flux data from land-based marine micrometeorological sites in categories depending on the type of land influence:1. CAT1: Marine data representing open sea,2. CAT2: Disturbed wave field resulting in physical properties different from open sea conditions and heterogeneity of water properties in the footprint region, and3. CAT3: Mixed land-sea footprint, very heterogeneous conditions and possible active carbon production/consumption.Characterization of data would be beneficial for combined analyses using several sites in coastal and marginal seas and evaluation/comparison of properties and dynamics. Aerosol fluxes are a useful contribution to characterizing a marine micrometeorological field station; for most conditions, they change sign between land and sea sectors. Measured fluxes from the land-based marine station Ostergarnsholm are used as an example of a land-based marine site to evaluate the categories and to present an example of differences between open sea and coastal conditions. At the Ostergarnsholm site the surface drag is larger for CAT2 and CAT3 than for CAT1 when wind speed is below 10m/s. The heat and humidity fluxes show a distinctive distinguished seasonal cycle; latent heat flux is larger for CAT2 and CAT3 compared to CAT1. The flux of carbon dioxide is large from the coastal and land-sea sectors, showing a large seasonal cycle and significant variability (compared to the open sea sector). Aerosol fluxes are partly dominated by sea spray emissions comparable to those observed at other open sea conditions.
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| 17. |
- Shao, Mingming, et al.
(författare)
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Atmospheric Fronts Shaping the (Sub)Mesoscale SST-Wind Coupling Over the Southern Ocean : Observational Case
- 2024
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Ingår i: Journal of Geophysical Research: Atmospheres. - : John Wiley & Sons. ; 129:8
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Tidskriftsartikel (refereegranskat)abstract
- Surface wind divergence is largely modulated by the sea surface temperature (SST) gradient through vertical momentum mixing and pressure adjustment. Here, the two mechanisms affecting the coupling strength between SST gradient and surface wind divergence are examined during an atmospheric front passage in the Southern Ocean. This event is also recorded by an uncrewed surface vehicle (USV). The reanalysis product (ERA5) revealed that downward momentum mixing is the dominant mechanism on the daily time scale. The coupling strength during the day when the atmospheric front passed over declined by 75%, compared to the adjacent days. This implies that the atmospheric front can partially attenuate the SST gradient effect on the surface wind divergence. Furthermore, a decade-long statistic also showed a decreasing trend of SST-wind coupling when the atmospheric fronts occur more. Additionally, after removing the mesoscale weather variation, the USV observations showed a remarkable SST imprint on the atmospheric boundary layer in the oceanic submesoscale regime, which denotes the scale below the deformation radius (∌16 km). The submesoscale air-sea interaction processes also displayed decreased air-sea coupling strength during atmospheric front passage. This is possible as the vertical velocity induced by the atmospheric front can compensate for the daily averaged uprising vertical velocity due to surface wind convergence. This analysis indicates that the atmospheric front can diminish the coupling between the SST gradient and surface wind divergence, which contrasts the existing statistical results showing that atmospheric fronts tend to enhance such coupling.
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| 18. |
- 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. - 1463-5003 .- 1463-5011.
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Tidskriftsartikel (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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| 19. |
- Wu, Lichuan, et al.
(författare)
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Atmospheric boundary layer turbulence closure scheme for wind-following swell conditions
- 2017
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Ingår i: Journal of the Atmospheric Sciences. - 0022-4928 .- 1520-0469. ; 74:7, s. 2363-2382
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Tidskriftsartikel (refereegranskat)abstract
- Over the ocean, atmospheric boundary layer turbulence can be altered by underlying waves. Under swell conditions, the impact of waves on the atmosphere is more complicated compared to that under wind-wave conditions. Based on large-eddy simulation (LES), the wind-following swell impact on the atmospheric boundary layer is investigated through three terms: swell-induced surface momentum flux, the vertical profile of swell-induced momentum flux, and the swell impact on atmospheric mixing. The swell-induced surface momentum flux displays a decreasing trend with increasing atmospheric convection. The swell-induced momentum flux decays approximately exponentially with height. Compared with atmospheric convection, the decay coefficient is more sensitive to wave age. Atmospheric mixing is enhanced under swell conditions relative to a flat stationary surface. The swell impact on the atmospheric boundary layer is incorporated into a turbulence closure parameterization through the three terms. The modified turbulence closure parameterization is introduced into a single-column atmospheric model to simulate LES cases. Adding only the swell impact on the atmospheric mixing has a limited influence on wind profiles. Adding both the impact of swell on the atmospheric mixing and the profile of swell-induced momentum flux significantly improves the agreement between the 1D atmospheric simulation results and the LES results, to some extent simulating the wave-induced low-level wind jet. It is concluded that the swell impact should be included in atmospheric numerical models.
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| 20. |
- Wu, Lichuan
(författare)
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Effect of atmosphere-wave-ocean/ice interactions on a polar low simulation over the Barents Sea
- 2021
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Ingår i: Atmospheric research. - : Elsevier. - 0169-8095 .- 1873-2895. ; 248
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Tidskriftsartikel (refereegranskat)abstract
- The impact of atmosphere-wave-ocean/ice interactions on the development of a hurricane-like polar low (PL) over the Barents Sea during 18–21 December 2002 is investigated using a fully coupled atmosphere-wave-ocean/ice model with five model settings. The atmosphere-wave-ocean/ice interactions have a marginal influence on the PL development when the baroclinic instability is a dominating factor. However, they do have an influence on the PL development when the role of baroclinic instability vanishes. The atmosphere-wave interactions have a limited influence on the PL intensity but they extend the size of the anticyclonic loop of the PL track. In contrast, the atmosphere-ocean interactions reduce the size of the track loop since the ice coverage is increased due to the atmosphere-ocean coupling which limits the northward movement of the PL. Besides, the increase of the ice coverage reduces the PL precipitation, in contrast, the wave coupling processes increase the PL precipitation. The atmosphere-ocean coupling processes enhance the PL intensity in term of the minimum sea level pressure which differs from previous studies that the atmosphere-ocean coupling has a negative feedback on the development of cyclones. The positive feedback from atmosphere-ocean coupling is more significant when the wave coupling processes are added into the model. The feedback from atmosphere-ocean coupling processes are determined by two processes: (1) heat flux induced sea surface cooling which has a negative feedback on the PL development, and (2) the strong wind-induced sea surface warming caused by the upper-ocean mixing when the temperature inversion exists in the ocean close to the ice edge. In this PL case, the wave coupling processes enhance the upper-ocean mixing and bring warm water to the surface in the area with ocean temperature inversions. Besides, the atmosphere-ocean coupling processes enhance the thermal wind of the PL and alter the vertical structure of the PL.
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| 21. |
- Wu, Lichuan, et al.
(författare)
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Impact of Air-Wave-Sea Coupling on the Simulation of Offshore Wind and Wave Energy Potentials
- 2020
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Ingår i: Atmosphere. - : MDPI. - 2073-4433. ; 11:4
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Tidskriftsartikel (refereegranskat)abstract
- Offshore wind and wave energy potentials are commonly simulated by atmosphere and wave stand-alone models, in which the Atmosphere Wave Ocean (AWO) dynamical coupling processes are neglected. Based on four experiments (simulated by UU-CM, Uppsala University-Coupled model) with four different coupling configurations between atmosphere, waves, and ocean, we found that the simulations of the wind power density (WPD) and wave potential energy (WPE) are sensitive to the AWO interaction processes over the North and Baltic Seas; in particular, to the atmosphere ocean coupling processes. Adding all coupling processes can change more than 25% of the WPE but only less than 5% of the WPD in four chosen coastal areas. The impact of the AWO coupling processes on the WPE and WPD changes significantly with the distance off the shoreline, and the influences vary with regions. From the simulations used in this study, we conclude that the AWO coupling processes should be considered in the simulation of WPE and WPD.
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| 22. |
- Wu, Lichuan
(författare)
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Impact of surface gravity waves on air-sea fluxes and upper-ocean mixing
- 2016
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Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Surface gravity waves play a vital role in the air-sea interaction. They can alter the turbulence ofthe bottom atmospheric layer as well as the upper-ocean layer. Accordingly, they can affect themomentum flux, heat fluxes, as well as the upper-ocean mixing. In most numerical models, waveinfluences are not considered or not fully considered. The wave influences on the atmosphereand the ocean are important for weather forecasts and climate studies. Here, different aspects ofwave impact on the atmosphere and the ocean are introduced into numerical models.In the first study, a wave-state-dependent sea spray generation function and Charnock co-efficient were applied to a wind stress parameterization under high wind speeds. The newlyproposed wind stress parameterization and a sea spray influenced heat flux parameterizationwere applied to an atmosphere-wave coupled model to study their influence on the simulationof mid-latitude storms. The new wind stress parameterization reduces wind speed simulationerror during high wind speed ranges and intensifies the storms. Adding the sea spray impacton heat fluxes improves the model performance concerning the air temperature. Adding the seaspray impact both on the wind stress and heat fluxes results in best model performance in allexperiments for wind speed, and air temperature.In the second study, the influence of surface waves on upper-ocean mixing was parameter-ized into a 1D k − ε ocean turbulence model though four processes (wave breaking, Stokes driftinteraction with the Coriolis force, Langmuir circulation, and stirring by non-breaking waves)based mainly on existing investigations. Considering all the effects of surface gravity waves,rather than just one effect, significantly improves model performance. The non-breaking-wave-induced mixing and Langmuir turbulence are the most important terms when considering theimpact of waves on upper-ocean mixing. Sensitivity experiments demonstrate that vertical pro-files of the Stokes drift calculated from 2D wave spectrum improve the model performancesignificantly compared with other methods of calculating the vertical profiles of the Stokes drift.Introducing the wave influences in modelling systems, the results verified against measure-ments. Concluding from these studies for the further model development, the wave influencesshould be taken into account to improve the model performance.
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| 23. |
- Wu, Lichuan
(författare)
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Introducing Surface Gravity Waves into Earth System Models
- 2017
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Surface gravity waves alter the turbulence of the bottom atmosphere and the upper ocean. Accordingly, they can affect momentum flux, heat fluxes, gas exchange and atmospheric mixing. However, in most state-of-the-art Earth System Models (ESMs), surface wave influences are not fully considered or even included. Here, applying surface wave influences into ESMs is investigated from different aspects.Tuning parameterisations for including instantaneous wave influences has difficulties to capture wave influences. Increasing the horizontal resolution of models intensifies storm simulations for both atmosphere-wave coupled (considering the influence of instantaneous wave-induced stress) and stand-alone atmospheric models. However, coupled models are more sensitive to the horizontal resolution than stand-alone atmospheric models.Under high winds, wave states have a big impact on the sea spray generation. Introducing a wave-state-dependent sea spray generation function and Charnock coefficient into a wind stress parameterisation improves the model performance concerning wind speed (intensifies storms). Adding sea spray impact on heat fluxes improves the simulation results of air temperature. Adding sea spray impact both on the wind stress and heat fluxes results in better model performance on wind speed and air temperature while compared to adding only one wave influence.Swell impact on atmospheric turbulence closure schemes should be taken into account through three terms: the atmospheric mixing length scale, the swell-induced momentum flux at the surface, and the profile of swell-induced momentum flux. Introducing the swell impact on the three terms into turbulence closure schemes shows a better performance than introducing only one of the influences.Considering all surface wave impacts on the upper-ocean turbulence (wave breaking, Stokes drift interaction with the Coriolis force, Langmuir circulation, and stirring by non-breaking waves), rather than just one effect, significantly improves model performance. The non-breaking-wave-induced mixing and Langmuir circulation are the most important terms when considering the impact of waves on upper-ocean mixing.Accurate climate simulations from ESMs are very important references for social and biological systems to adapt the climate change. Comparing simulation results with measurements shows that adding surface wave influences improves model performance. Thus, an accurate description of all important wave impact processes should be correctly represented in ESMs, which are important tools to describe climate and weather. Reducing the uncertainties of simulation results from ESMs through introducing surface gravity wave influences is necessary.
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| 24. |
- Wu, Lichuan, et al.
(författare)
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Modeling the Vulnerability of Waterway Networks
- 2014
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Ingår i: Journal of waterway, port, coastal, and ocean engineering. - 0733-950X .- 1943-5460. ; 140:4, s. 04014012-
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Tidskriftsartikel (refereegranskat)abstract
- In some areas, rivers and canals interweave into a network, making inland waterway transportation feasible. Significant losses will occur if a vulnerable waterway (where vulnerability is defined in terms of susceptibility to interference and difficulty in restoring the initial state) that is vital to a network is blocked. System vulnerabilities combined with hazard factors trigger disasters; therefore, reducing the vulnerability of a network system is a useful means of reducing major losses. In this paper, a model to calculate vulnerability based on inherent characteristics of waterways such as channel connectivity, transportation efficiency, and economic cost is developed. Three influence factors-importance, efficiency contribution, and loss-are used to build a vulnerability assessment model in which the relative vulnerabilities of various waterways can be assessed and the most vulnerable waterway can be found. Using this model, a simple waterway network is tested to identify vulnerable waterways. (C) 2014 American Society of Civil Engineers.
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| 25. |
- Wu, Lichuan, et al.
(författare)
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Ocean‐Wave‐Atmosphere Interaction Processes in a Fully Coupled Modeling System
- 2019
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Ingår i: Journal of Advances in Modeling Earth Systems. - 1942-2466. ; 11:11, s. 3852-3874
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Tidskriftsartikel (refereegranskat)abstract
- A high‐resolution coupled ocean‐wave‐atmosphere model (Uppsala University Coupled model, UU‐CM) of the Baltic Sea and the North Sea with improved representation of ocean‐wave‐atmosphere interaction processes is presented. In the UU‐CM model, the stress on the air‐sea interface is estimated as a balance of four stress terms, that is, the air‐side stress, ocean‐side stress, wave‐supported stress (absorption of momentum by the wave field), and the momentum flux from waves to currents (breaking waves). The vector differences between these four stress terms are considered in the coupled system. The turbulent kinetic energy flux induced by wave breaking, the Stokes‐Coriolis force and the Stokes drift material advection terms are added to the ocean circulation model component. Based on two‐month‐long (January and July) simulations, we find that the ocean‐wave‐atmosphere coupling has a significant influence on coastal areas. The coupled system captures the influence of surface currents and local systems such as coastal upwelling and their impact on the atmosphere. The wave‐current interaction enhances the upper ocean mixing and reduces the sea surface temperature in July significantly. However, the pattern of the wave‐current processes influences on the ocean current and waves are complex due to the stress differences in both magnitude and direction.
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| 26. |
- Wu, Lichuan, et al.
(författare)
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Surface Wave Impact When Simulating Midlatitude Storm Development
- 2017
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Ingår i: Journal of Atmospheric and Oceanic Technology. - 0739-0572 .- 1520-0426. ; 34:1, s. 233-248
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Tidskriftsartikel (refereegranskat)abstract
- Surface gravity waves, present at the air–sea interface, can affect the momentum flux and heat fluxes by modifying turbulence in the lower layers of the atmosphere. How to incorporate wave impacts into model parameterizations is still an open issue. In this study, the influence of a dynamic roughness length (considering instantaneous wave-induced stress), horizontal resolution, and the coupling time resolution between waves and the atmosphere on storm simulations are investigated using sensitivity experiments. Based on the sim- ulations of six midlatitude storms using both an atmosphere–wave coupled model and an atmospheric stand- alone model, the impacts are investigated. Adding the wave-induced stress weakens the storm intensity. Applying a roughness length tuned to an average friction velocity is not enough to capture the simulation results from ‘‘true’’ wave-related roughness length. High-horizontal-resolution models intensify the simula- tion of storms, which is valid for both coupled and uncoupled models. Compared with the atmospheric stand- alone model, the coupled model (considering the influence of dynamic roughness length) is more sensitive to the model horizontal resolution. During reasonable ranges, the coupling time resolution does not have a significant impact on the storm intensity based on the limited experiments used in this study. It is concluded that the dynamic wave influence (instantaneous wave influence) and the model resolution should be taken into account during the development of forecast and climate models.
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| 27. |
- Wu, Lichuan, et al.
(författare)
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Swell impact on wind stress and atmospheric mixing in a regional coupled atmosphere-wave model
- 2016
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Ingår i: Journal of Geophysical Research - Oceans. - 2169-9275 .- 2169-9291. ; 121:7, s. 4633-4648
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Tidskriftsartikel (refereegranskat)abstract
- Over the ocean, the atmospheric turbulence can be significantly affected by swell waves. Change in the atmospheric turbulence affects the wind stress and atmospheric mixing over swell waves. In this study, the influence of swell on atmospheric mixing and wind stress is introduced into an atmosphere-wave-coupled regional climate model, separately and combined. The swell influence on atmospheric mixing is introduced into the atmospheric mixing length formula by adding a swell-induced contribution to the mixing. The swell influence on the wind stress under wind-following swell, moderate-range wind, and near-neutral and unstable stratification conditions is introduced by changing the roughness length. Five year simulation results indicate that adding the swell influence on atmospheric mixing has limited influence, only slightly increasing the near-surface wind speed; in contrast, adding the swell influence on wind stress reduces the near-surface wind speed. Introducing the wave influence roughness length has a larger influence than does adding the swell influence on mixing. Compared with measurements, adding the swell influence on both atmospheric mixing and wind stress gives the best model performance for the wind speed. The influence varies with wave characteristics for different sea basins. Swell occurs infrequently in the studied area, and one could expect more influence in high-swell-frequency areas (i.e., low-latitude ocean). We conclude that the influence of swell on atmospheric mixing and wind stress should be considered when developing climate models.
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| 28. |
- Wu, Lichuan, et al.
(författare)
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The impact of waves and sea spray on modelling storm track and development
- 2015
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Ingår i: Tellus. Series A, Dynamic meteorology and oceanography. - : Stockholm University Press. - 0280-6495 .- 1600-0870. ; 67
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Tidskriftsartikel (refereegranskat)abstract
- In high wind speed conditions, sea spray generated by intensely breaking waves greatly influences the wind stress and heat fluxes. Measurements indicate that the drag coefficient decreases at high wind speeds. The sea spray generation function (SSGF), an important term of wind stress parameterisation at high wind speeds, is usually treated as a function of wind speed/friction velocity. In this study, we introduce a wave-state-dependent SSGF and wave-age-dependent Charnock number into a high wind speed–wind stress parameterisation. The newly proposed wind stress parameterisation and sea spray heat flux parameterisation were applied to an atmosphere–wave coupled model to study the mid-latitude storm development of six storm cases. Compared with measurements from the FINO1 platform in the North Sea, the new wind stress parameterisation can reduce wind speed simulation errors in the high wind speed range. Considering only sea spray impact on wind stress (and not on heat fluxes) will intensify the storms (in terms of minimum sea level pressure and maximum wind speed), but has little effect on the storm tracks. Considering the impact of sea spray on heat fluxes only (not on wind stress) can improve the model performance regarding air temperature, but it has little effect on the storm intensity and storm track performance. If the impact of sea spray on both the wind stress and heat fluxes is taken into account, the model performs best in all experiments for minimum sea level pressure, maximum wind speed and air temperature.
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| 29. |
- Wu, Lichuan, et al.
(författare)
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The Redistribution of Air-€“Sea Momentum and Turbulent Kinetic Energy Fluxes by Ocean Surface Gravity Waves
- 2022
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Ingår i: Journal of Physical Oceanography. - : American Meteorological Society. ; 52:7, s. 1483-1496
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Tidskriftsartikel (refereegranskat)abstract
- The momentum flux to the ocean interior is commonly assumed to be identical to the momentum flux lost from the atmosphere in traditional atmosphere, ocean, and coupled models. However, ocean surface gravity waves (hereafter waves) can alter the magnitude and direction of the ocean-side stress (tau(oc)) from the air-side stress (tau(a)). This is rarely considered in coupled climate and forecast models. Based on a 30-yr wave hindcast, the redistribution of the global wind stress and turbulent kinetic energy (TKE) flux by waves was investigated. Waves play a more important role in the windy oceans in middle and high latitudes than that in the oceans in the tropics (i.e., the central portion of the Pacific and Atlantic Oceans). On average, the relative difference between tau(oc) and tau(a), gamma(tau), can be up to 6% in middle and high latitudes. The frequency of occurrence of gamma(tau) > 9% can be up to 10% in the windy extratropics. The directional difference between tau(oc) and tau(a) exceeds 3.5 degrees in the middle and high latitudes 10% of the time. The difference between tau(oc) and tau(a) becomes more significant closer to the coasts of the continents due to strong wind gradients. The friction velocity-based approach overestimates (underestimates) the breaking-induced TKE flux in the tropics (middle and high latitudes). The findings presented in the current study show that coupled climate and Earth system models would clearly benefit from the inclusion of a wave model. Significance StatementThe purpose of this study is to investigate the redistribution of the global wind stress and turbulent kinetic energy flux due to surface waves based on a 30-yr wave hindcast. The mean relative difference of the magnitude between the air-side and ocean-side stress is up to 6% with a 90th percentile of more than 9% in the windy extratropics. Due to strong wind gradients, the redistributive role of waves in the stress becomes more significant closer to coasts. The results indicate that we should consider the redistributive role of waves in the momentum and energy fluxes in climate and Earth system models since they are the key elements in the predictability of weather forecasting models and climate models.
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| 30. |
- Wu, Lichuan, et al.
(författare)
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Upper-ocean mixing due to surface gravity waves
- 2015
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Ingår i: Journal of Geophysical Research - Oceans. - 2169-9275 .- 2169-9291. ; 120:12, s. 8210-8228
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Tidskriftsartikel (refereegranskat)abstract
- Surface gravity waves play an important role in the lower layer of the atmosphere and the upper layer of the ocean. Surface waves effect upper-ocean mixing mainly through four processes: wave breaking, Stokes drift interaction with the Coriolis force, Langmuir circulation, and stirring by nonbreaking waves. We introduce the impact of these four processes into a 1-D ocean turbulence model. The parameterizations used are based mainly on existing investigations. Comparison of simulation results and measurements demonstrates that considering all the effects of waves, rather than just one effect, significantly improves model performance. The nonbreaking-wave-induced mixing and Langmuir turbulence are the most important terms when considering the impact of waves on upper-ocean mixing. Under high-wave conditions, the turbulent mixing induced by nonbreaking waves can be of the same order of magnitude as the viscosity induced by other terms at the surface. Nonbreaking waves contribute very little to shear production and their impact is negligible in the models. Sensitivity experiments demonstrate that the vertical profile of the Stokes drift calculated from the 2-D wave spectrum improves model performance significantly compared with other methods of introducing wave effects.
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| 31. |
- Wu, Lichuan, et al.
(författare)
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Vertical Profiles of Wave-Coherent Momentum Flux and Velocity Variances in the Marine Atmospheric Boundary Laye
- 2018
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Ingår i: Journal of Physical Oceanography. - 0022-3670 .- 1520-0485. ; 48:3, s. 625-641
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Tidskriftsartikel (refereegranskat)abstract
- The wave-coherent momentum flux and velocity variances are investigated using a theoretical model and open-ocean measurements. The spectrum-integrated wave-coherent (SIWC) momentum flux and velocity variances decay roughly exponentially with height. The exponential decay coefficients of the SIWC momentum flux and velocity variances decrease with increasing peak wavenumber. The phases of the wave-coherent horizontal (vertical) velocity fluctuations are approximately 180° (90°) under waves with wind-wave angle |α1| < 90°. In general, the ratio of the SIWC momentum flux to the total momentum flux under swell conditions is higher than that under wind-wave conditions at the same height. At a height of 9.9 m, the SIWC vertical (horizontal) velocity variances can exceed 30% (10%) of the total vertical (horizontal) velocity variances at high wave ages. The impact of SIWC momentum flux on wind profiles is determined mainly by the surface SIWC momentum flux ratio, the decay coefficient of the SIWC momentum flux, and the sea surface roughness length, with the first two factors being dominant. The results of this study suggest a methodology for parameterizing the SIWC momentum flux and the total momentum flux over the ocean. These results are important for simulating the marine atmospheric boundary layer and should be used in model development.
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| 32. |
- Wu, Lichuan, et al.
(författare)
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Wave effects on coastal upwelling and water level
- 2019
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Ingår i: Ocean Modelling. - : Elsevier BV. - 1463-5003 .- 1463-5011. ; 140
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Tidskriftsartikel (refereegranskat)abstract
- Traditional atmosphere, ocean and wave models are run independently of each other. This means that the energy and momentum fluxes do not fully account for the impact of the oceanic wave field at the air-sea interface. In this study, the Stokes drift impact on mass and tracer advection, the Stokes-Coriolis forcing, and the sea-state-dependent momentum and energy fluxes are introduced into an ocean circulation model and tested for a domain covering the Baltic Sea and the North Sea. Sensitivity experiments are designed to investigate the influence on the simulation of storms and Baltic Sea upwelling. Inclusion of wave effects improves the model performance compared with the stand-alone circulation model in terms of sea level height, temperature and circulation. The direct sea-state-dependent momentum and turbulent kinetic energy fluxes prove to be of higher importance than the Stokes drift related effects investigated in this study (i.e., Stokes-Coriolis forcing and Stokes drift advection on tracers and on mass). The latter affects the mass and tracer advection but largely balances the influence of the Stokes-Coriolis forcing. The upwelling frequency changes by > 10% along the Swedish coast when wave effects are included. In general, the strong (weak) upwelling probability is reduced (increased) when adding the wave effects. From the results, we conclude that inclusion of wave effects can be important for regional, high-resolution ocean models even on short time scales, suggesting that they should be introduced in operational ocean circulation models. However, care should be taken when introducing the Stokes-Coriolis forcing as it should be balanced by the Stokes drift in mass and tracer advection.
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| 33. |
- Wu, Lichuan, et al.
(författare)
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Wind Profile in the Wave Boundary Layer and Its Application in a Coupled Atmosphere-Wave Model
- 2022
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Ingår i: Journal of Geophysical Research - Oceans. - : American Geophysical Union (AGU). - 2169-9275 .- 2169-9291. ; 127:2
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Tidskriftsartikel (refereegranskat)abstract
- Current models cannot capture well the impacts of wind waves on the atmospheric boundary layer. Here, we proposed a new turbulence closure model to estimate the wind stress in the wave boundary layer from viscous stress, shear-induced turbulent stress, wind-sea induced stress, and swell-induced upward stress separately. The misalignment between the wind stress and wind is also considered in the model. Single-column simulations indicate that (a) the swell-induced upward momentum flux increases the surface wind and changes the wind direction, (b) the misalignment between the upward momentum flux and wind has a more significant impact on the wind profile than that from the downward momentum flux, and (c) the impact of swell-induced upward momentum flux decreases with atmospheric convection. The proposed closure scheme was implemented into an atmosphere-wave coupled model. A month-long simulation over the ocean off California shows that the surface wind can be altered up to 5% by ocean surface gravity waves.Plain Language SummaryAir-sea interactions are important for weather and climate predictions since they control the momentum and energy transfer between the atmosphere and the ocean. In current models, the momentum flux in the atmospheric boundary layer is estimated by turbulence closure models, which were developed heavily based on measurements over land. However, those turbulence closure models often fail to capture the momentum flux and wind profile in the marine atmospheric boundary layer due to wave impacts. In this study, we developed a new turbulence closure model that can capture the impacts of swell-induced upward momentum flux and the misalignment angle between the stress and wind as well as the swell-induced low-level wind jet. A month-long simulation indicates that considering the wave, impacts can alter the surface wind up to 5%. Thus, it is necessary to implement those wave impacts into ocean, weather, and climate models.
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| 34. |
- Zhang, Shuping, et al.
(författare)
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Mapping coastal upwelling in the Baltic Sea from 2002 to 2020 using remote sensing data
- 2022
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Ingår i: International Journal of Applied Earth Observation and Geoinformation. - : Elsevier. - 1569-8432 .- 1872-826X. ; 114
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Tidskriftsartikel (refereegranskat)abstract
- Coastal upwelling (CU) is an elementary phenomenon in coastal waters. CU brings up deep, often cold, saline water rich of nutrients and carbon, and plays a vital role in local air-sea exchange of gases and heat, marine ecosystem maintenance, and ocean physical dynamics. In this study, regional CU in the Baltic Sea was mapped on the daily MODIS SST from 2002 to 2020, using a method modified developed by Lehmann et al. (2012). Based on the individual CU event detected, the spatiotemporal distribution of CU in the Baltic Sea was depicted, the CU-wind relationship and potential CU drivers in the Baltic Sea on different temporal scale were analyzed. The results found that: 1) The modified approach can effectively delineate the CUs formed by upwelled cold water; 2) The 19 zones delineated with frequent CU occurrences aligned well with previous study and the overall CU occurrence spatial heterogeneity was casted by the different directional relationship between the local coastline and wind; 3) The occurrences of the CU detected in this study showed strong seasonality and primarily driven by SST seasonality and then intensified by local wind in fall; 4) The interannual difference of CU occurrences were affected by heatwaves and its monthly timing. The CUs detected in this study have a high potential for facilitating investigations with respect to oceanic modeling, air-sea exchange of heat and greenhouse gases, and physical dynamics in the Baltic Sea.
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