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  • 1.
    Cai, Yongqing
    et al.
    Wuhan Univ Technol, Sch Nav, Wuhan, Peoples R China.; Hubei Key Lab Inland Shipping Technol, Wuhan, Peoples R China.; Natl Engn Res Ctr Water Transport Safety, Wuhan, Peoples R China..
    Wen, Yuanqiao
    Wuhan Univ Technol, Sch Nav, Wuhan, Peoples R China.; Hubei Key Lab Inland Shipping Technol, Wuhan, Peoples R China.; Natl Engn Res Ctr Water Transport Safety, Wuhan, Peoples R China..
    Wu, Lichuan
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, LUVAL.
    Zhou, Chunhui
    Wuhan Univ Technol, Sch Nav, Wuhan, Peoples R China.; Hubei Key Lab Inland Shipping Technol, Wuhan, Peoples R China.; Natl Engn Res Ctr Water Transport Safety, Wuhan, Peoples R China..
    Zhang, Fang
    Wuhan Univ Technol, Sch Nav, Wuhan, Peoples R China.; Hubei Key Lab Inland Shipping Technol, Wuhan, Peoples R China.; Natl Engn Res Ctr Water Transport Safety, Wuhan, Peoples R China..
    Impact of wave breaking on upper-ocean turbulence2017In: Journal of Geophysical Research - Oceans, ISSN 2169-9275, E-ISSN 2169-9291, Vol. 122, no 2, p. 1513-1528Article in journal (Refereed)
    Abstract [en]

    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.

  • 2.
    Jeworrek, Julia
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, LUVAL.
    Wu, Lichuan
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, LUVAL.
    Dieterich, Christian
    Swedish Meteorol & Hydrol Inst, S-60176 Norrkoping, Sweden.
    Rutgersson, Anna
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, LUVAL.
    Characteristics of convective snow bands along the Swedish east coast2017In: Earth System Dynamics, ISSN 2190-4979, E-ISSN 2190-4987, Vol. 8, p. 163-175Article in journal (Refereed)
    Abstract [en]

    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.

  • 3.
    Rutgersson, Anna
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, LUVAL.
    Pettersson, Heidi
    Nilsson, Erik O.
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, LUVAL.
    Bergström, Hans
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, LUVAL.
    Wallin, Marcus
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, LUVAL.
    Nilsson, Douglas
    Sahlée, Erik
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, LUVAL.
    Wu, Lichuan
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, LUVAL.
    Mårtensson, E. Monica
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, LUVAL.
    Using land-based stations for air–sea interaction studies2020In: Tellus. Series A, Dynamic meteorology and oceanography, ISSN 0280-6495, E-ISSN 1600-0870, Vol. 72, no 1Article in journal (Refereed)
  • 4.
    Wen, Yuanqiao
    et al.
    Wuhan Univ Technol, Sch Nav, Wuhan, Hubei, Peoples R China.;Hubei Key Lab Inland Shipping Technol, Wuhan, Hubei, Peoples R China..
    Geng, Xiaoqiao
    Wuhan Univ Technol, Sch Nav, Wuhan, Hubei, Peoples R China..
    Wu, Lichuan
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, LUVAL.
    Yip, Tsz Leung
    Hong Kong Polytech Univ, Dept Logist & Maritime Studies, Hong Kong, Hong Kong, Peoples R China..
    Huang, Liang
    Wuhan Univ Technol, Sch Nav, Wuhan, Hubei, Peoples R China..
    Wu, Dingyong
    Wuhan Univ Technol, Sch Nav, Wuhan, Hubei, Peoples R China..
    Green routing design in short seas2017In: International Journal of Shipping and Transport Logistics, ISSN 1756-6517, E-ISSN 1756-6525, Vol. 9, no 3, p. 371-390Article in journal (Refereed)
    Abstract [en]

    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.

  • 5.
    Wu, Lichuan
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, LUVAL.
    Impact of surface gravity waves on air-sea fluxes and upper-ocean mixing2016Licentiate thesis, comprehensive summary (Other academic)
    Abstract [en]

    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.

    List of papers
    1. The impact of waves and sea spray on modelling storm track and development
    Open this publication in new window or tab >>The impact of waves and sea spray on modelling storm track and development
    2015 (English)In: Tellus. Series A, Dynamic meteorology and oceanography, ISSN 0280-6495, E-ISSN 1600-0870, Vol. 67, article id 27967Article in journal (Refereed) Published
    Abstract [en]

    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.

    Keywords
    sea spray, wind stress, heat fluxes, storms
    National Category
    Earth and Related Environmental Sciences
    Identifiers
    urn:nbn:se:uu:diva-263091 (URN)10.3402/tellusa.v67.27967 (DOI)000361746300001 ()
    Funder
    Swedish Research Council
    Available from: 2015-09-25 Created: 2015-09-25 Last updated: 2017-12-01Bibliographically approved
    2. Upper-ocean mixing due to surface gravity waves
    Open this publication in new window or tab >>Upper-ocean mixing due to surface gravity waves
    2015 (English)In: Journal of Geophysical Research - Oceans, ISSN 2169-9275, E-ISSN 2169-9291, Vol. 120, no 12, p. 8210-8228Article in journal (Refereed) Published
    Abstract [en]

    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.

    Keywords
    ocean mixing; nonbreaking waves; Langmuir circulation; Coriolis-Stokes forcing; breaking waves
    National Category
    Meteorology and Atmospheric Sciences
    Identifiers
    urn:nbn:se:uu:diva-270913 (URN)10.1002/2015JC011329 (DOI)000369153200027 ()
    Funder
    Swedish Research Council, 2012-3902
    Available from: 2016-01-05 Created: 2016-01-05 Last updated: 2017-12-01Bibliographically approved
  • 6.
    Wu, Lichuan
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, LUVAL.
    Introducing Surface Gravity Waves into Earth System Models2017Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    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.

    List of papers
    1. Surface Wave Impact When Simulating Midlatitude Storm Development
    Open this publication in new window or tab >>Surface Wave Impact When Simulating Midlatitude Storm Development
    2017 (English)In: Journal of Atmospheric and Oceanic Technology, ISSN 0739-0572, E-ISSN 1520-0426, Vol. 34, no 1, p. 233-248Article in journal, News item (Refereed) Published
    Abstract [en]

    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.

    National Category
    Meteorology and Atmospheric Sciences
    Identifiers
    urn:nbn:se:uu:diva-313154 (URN)10.1175/JTECH-D-16-0070.1 (DOI)000391826300016 ()
    Funder
    Swedish Research Council, 2012-3902
    Available from: 2017-01-17 Created: 2017-01-17 Last updated: 2017-11-29Bibliographically approved
    2. The impact of waves and sea spray on modelling storm track and development
    Open this publication in new window or tab >>The impact of waves and sea spray on modelling storm track and development
    2015 (English)In: Tellus. Series A, Dynamic meteorology and oceanography, ISSN 0280-6495, E-ISSN 1600-0870, Vol. 67, article id 27967Article in journal (Refereed) Published
    Abstract [en]

    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.

    Keywords
    sea spray, wind stress, heat fluxes, storms
    National Category
    Earth and Related Environmental Sciences
    Identifiers
    urn:nbn:se:uu:diva-263091 (URN)10.3402/tellusa.v67.27967 (DOI)000361746300001 ()
    Funder
    Swedish Research Council
    Available from: 2015-09-25 Created: 2015-09-25 Last updated: 2017-12-01Bibliographically approved
    3. Swell impact on wind stress and atmospheric mixing in a regional coupled atmosphere-wave model
    Open this publication in new window or tab >>Swell impact on wind stress and atmospheric mixing in a regional coupled atmosphere-wave model
    2016 (English)In: Journal of Geophysical Research - Oceans, ISSN 2169-9275, E-ISSN 2169-9291, Vol. 121, no 7, p. 4633-4648Article in journal (Refereed) Published
    Abstract [en]

    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.

    Keywords
    air-sea interaction; swell waves; wind stress; atmospheric mixing
    National Category
    Oceanography, Hydrology and Water Resources Meteorology and Atmospheric Sciences
    Identifiers
    urn:nbn:se:uu:diva-302007 (URN)10.1002/2015JC011576 (DOI)000383468500013 ()
    Funder
    Swedish Research Council, 2012-3902
    Available from: 2016-08-27 Created: 2016-08-27 Last updated: 2018-01-10Bibliographically approved
    4. Atmospheric boundary layer turbulence closure scheme for wind-following swell conditions
    Open this publication in new window or tab >>Atmospheric boundary layer turbulence closure scheme for wind-following swell conditions
    2017 (English)In: Journal of Atmospheric Sciences, ISSN 0022-4928, E-ISSN 1520-0469, Vol. 74, no 7, p. 2363-2382Article in journal (Refereed) Published
    Abstract [en]

    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.

    National Category
    Meteorology and Atmospheric Sciences
    Identifiers
    urn:nbn:se:uu:diva-314757 (URN)10.1175/JAS-D-16-0308.1 (DOI)000405556700015 ()
    Funder
    Swedish Research Council, 2012-3902
    Available from: 2017-02-06 Created: 2017-02-06 Last updated: 2017-10-24Bibliographically approved
    5. Upper-ocean mixing due to surface gravity waves
    Open this publication in new window or tab >>Upper-ocean mixing due to surface gravity waves
    2015 (English)In: Journal of Geophysical Research - Oceans, ISSN 2169-9275, E-ISSN 2169-9291, Vol. 120, no 12, p. 8210-8228Article in journal (Refereed) Published
    Abstract [en]

    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.

    Keywords
    ocean mixing; nonbreaking waves; Langmuir circulation; Coriolis-Stokes forcing; breaking waves
    National Category
    Meteorology and Atmospheric Sciences
    Identifiers
    urn:nbn:se:uu:diva-270913 (URN)10.1002/2015JC011329 (DOI)000369153200027 ()
    Funder
    Swedish Research Council, 2012-3902
    Available from: 2016-01-05 Created: 2016-01-05 Last updated: 2017-12-01Bibliographically approved
  • 7.
    Wu, Lichuan
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, LUVAL.
    Breivik, Øyvind
    Norwegian Meteorological Institute; Geophysical Institute, University of Bergen.
    Rutgersson, Anna
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, LUVAL.
    Ocean‐Wave‐Atmosphere Interaction Processes in a Fully Coupled Modeling System2019In: Journal of Advances in Modeling Earth Systems, ISSN 1942-2466, Vol. 11, no 11, p. 3852-3874Article in journal (Refereed)
    Abstract [en]

    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.

  • 8.
    Wu, Lichuan
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, LUVAL.
    Hristov, Tihomir
    The Johns Hopkins University, Baltimore, Department of Mechanical Engineering, Maryland.
    Rutgersson, Anna
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, LUVAL.
    Vertical Profiles of Wave-Coherent Momentum Flux and Velocity Variances in the Marine Atmospheric Boundary Laye2018In: Journal of Physical Oceanography, ISSN 0022-3670, E-ISSN 1520-0485, Vol. 48, no 3, p. 625-641Article in journal (Refereed)
    Abstract [en]

    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.

  • 9.
    Wu, Lichuan
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, LUVAL.
    Rutgersson, Anna
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, LUVAL.
    Nilsson, Erik
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, LUVAL.
    Atmospheric boundary layer turbulence closure scheme for wind-following swell conditions2017In: Journal of Atmospheric Sciences, ISSN 0022-4928, E-ISSN 1520-0469, Vol. 74, no 7, p. 2363-2382Article in journal (Refereed)
    Abstract [en]

    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.

  • 10.
    Wu, Lichuan
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, LUVAL.
    Rutgersson, Anna
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, LUVAL.
    Sahlee, Erik
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, LUVAL.
    Larsen, Xiaoli
    Danish Tech Univ, Wind Energy Dept, Resource Assessment Modeling Sect, Riso Campus, Roskilde, Denmark.
    Swell impact on wind stress and atmospheric mixing in a regional coupled atmosphere-wave model2016In: Journal of Geophysical Research - Oceans, ISSN 2169-9275, E-ISSN 2169-9291, Vol. 121, no 7, p. 4633-4648Article in journal (Refereed)
    Abstract [en]

    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.

  • 11.
    Wu, Lichuan
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, LUVAL.
    Rutgersson, Anna
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, LUVAL.
    Sahlée, Erik
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, LUVAL.
    Upper-ocean mixing due to surface gravity waves2015In: Journal of Geophysical Research - Oceans, ISSN 2169-9275, E-ISSN 2169-9291, Vol. 120, no 12, p. 8210-8228Article in journal (Refereed)
    Abstract [en]

    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.

  • 12.
    Wu, Lichuan
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, LUVAL.
    Rutgersson, Anna
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, LUVAL.
    Sahlée, Erik
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, LUVAL.
    Larsén, Xiaoli Guo
    The impact of waves and sea spray on modelling storm track and development2015In: Tellus. Series A, Dynamic meteorology and oceanography, ISSN 0280-6495, E-ISSN 1600-0870, Vol. 67, article id 27967Article in journal (Refereed)
    Abstract [en]

    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.

  • 13.
    Wu, Lichuan
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, LUVAL.
    Sproson, David
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, LUVAL.
    Sahleé, Erik
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, LUVAL.
    Rutgersson, Anna
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, LUVAL.
    Surface Wave Impact When Simulating Midlatitude Storm Development2017In: Journal of Atmospheric and Oceanic Technology, ISSN 0739-0572, E-ISSN 1520-0426, Vol. 34, no 1, p. 233-248Article in journal (Refereed)
    Abstract [en]

    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.

  • 14.
    Wu, Lichuan
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, LUVAL.
    Staneva, Joanna
    Helmholtz Zentrum Geesthacht, Inst Coastal Res, Geesthacht, Germany.
    Breivik, Oyvind
    Norwegian Meteorol Inst, Oslo, Norway;Univ Bergen, Geophys Inst, Bergen, Norway.
    Rutgersson, Anna
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, LUVAL.
    Nurser, A. J. George
    Natl Oceanog Ctr, Southampton, Hants, England.
    Clementi, Emanuela
    EuroMediterranean Ctr Climate Change CMCC, Bologna, Italy.
    Madec, Gurvan
    CNRS, LOcean IPSL, Paris, France.
    Wave effects on coastal upwelling and water level2019In: Ocean Modelling, ISSN 1463-5003, E-ISSN 1463-5011, Vol. 140, article id UNSP 101405Article in journal (Refereed)
    Abstract [en]

    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.

  • 15.
    Wu, Lichuan
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, LUVAL.
    Wen, Yuanqiao
    Zhou, Chunhui
    Xiao, Changshi
    Zhang, Jinfeng
    Modeling the Vulnerability of Waterway Networks2014In: Journal of waterway, port, coastal, and ocean engineering, ISSN 0733-950X, E-ISSN 1943-5460, Vol. 140, no 4, p. 04014012-Article in journal (Refereed)
    Abstract [en]

    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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