Impact of Surface Waves on Wind Stress under Low to Moderate Wind Conditions

2020 ◽  
Author(s):  
Sheng Chen ◽  
Fangli Qiao ◽  
Wenzheng Jiang ◽  
Jingsong Guo ◽  
Dejun Dai
Keyword(s):  
Surface Waves ◽  
Wind Stress ◽  
Climate Models ◽  
Similarity Theory ◽  
Ocean Surface Waves ◽  
China Sea ◽  
Wind Speeds ◽  
Mean Sea Surface ◽  
Wind Profiles ◽  
The Impact

<p>The impact of ocean surface waves on wind stress at the air–sea interface under low to moderate wind<br>conditions was systematically investigated based on a simple constant flux model and flux measurements<br>obtained from two coastal towers in the East China Sea and South China Sea. It is first revealed that the<br>swell-induced perturbations can reach a height of nearly 30m above the mean sea surface, and these perturbations<br>disturb the overlying airflow under low wind and strong swell conditions. The wind profiles severely<br>depart from the classical logarithmic profiles, and the deviations increase with the peak wave phase speeds. At<br>wind speeds of less than 4 m/s, an upward momentumtransfer from the wave to the atmosphere is predicted,<br>which is consistent with previous studies. A comparison between the observations and model indicates that<br>the wind stress calculated by the model is largely consistent with the observational wind stress when considering<br>the effects of surface waves, which provides a solution for accurately calculating wind stress in ocean<br>and climate models. Furthermore, the surface waves at the air–sea interface invalidate the traditional<br>Monin–Obukhov similarity theory (MOST), and this invalidity decreases as observational height increases.</p>

Impact of Surface Waves on Wind Stress under Low to Moderate Wind Conditions

2019 ◽  
Vol 49 (8) ◽  
pp. 2017-2028 ◽  
Author(s):  
Sheng Chen ◽  
Fangli Qiao ◽  
Wenzheng Jiang ◽  
Jingsong Guo ◽  
Dejun Dai
Keyword(s):  
Surface Waves ◽  
Wind Stress ◽  
Climate Models ◽  
Similarity Theory ◽  
Ocean Surface Waves ◽  
China Sea ◽  
Wind Speeds ◽  
Mean Sea Surface ◽  
Wind Profiles ◽  
The Impact

AbstractThe impact of ocean surface waves on wind stress at the air–sea interface under low to moderate wind conditions was systematically investigated based on a simple constant flux model and flux measurements obtained from two coastal towers in the East China Sea and South China Sea. It is first revealed that the swell-induced perturbations can reach a height of nearly 30 m above the mean sea surface, and these perturbations disturb the overlying airflow under low wind and strong swell conditions. The wind profiles severely depart from the classical logarithmic profiles, and the deviations increase with the peak wave phase speeds. At wind speeds of less than 4 m s−1, an upward momentum transfer from the wave to the atmosphere is predicted, which is consistent with previous studies. A comparison between the observations and model indicates that the wind stress calculated by the model is largely consistent with the observational wind stress when considering the effects of surface waves, which provides a solution for accurately calculating wind stress in ocean and climate models. Furthermore, the surface waves at the air–sea interface invalidate the traditional Monin–Obukhov similarity theory (MOST), and this invalidity decreases as observational height increases.

Coupled processes in an ocean-sea ice-wave configuration

2021 ◽  
Author(s):  
Stefanie Rynders ◽  
Yevgeny Aksenov ◽  
Andrew Coward
Keyword(s):  
Sea Ice ◽  
Surface Waves ◽  
Wave Attenuation ◽  
Computational Cost ◽  
Breaking Waves ◽  
Coupled Processes ◽  
Computational Power ◽  
Marine Systems ◽  
Ocean Surface Waves ◽  
The Impact

<p>Marginal ice zones are areas with many interactions between ocean, surface waves, sea ice and atmosphere. Increasing computational power makes it possible to perform increasingly complex simulations of marine systems, with more components of the climate system that are more interacting. We have produced a set of increasingly coupled simulations with NEMO, CICE and WW3, exchanging more and more variables. The configuration is global at 1 degree resolution. The focus is on wave attenuation in sea ice and the impact of using modelled wave height for ocean mixing due to breaking waves. The example simulations give an idea of the possible impact on the simulated state versus the still considerable computational cost.</p>

A Package of New Universal Non-Iterative Parametrizations for Stable Surface Layer Transfer Coefficients of Momentum, Heat and Moisture in Numerical Earth System Models

2021 ◽  
Author(s):  
Vladimir Gryanik ◽  
Christof Luepkes ◽  
Andrey Grachev ◽  
Dmitry Sidorenko
Keyword(s):  
Climate Models ◽  
Similarity Theory ◽  
Weather Prediction ◽  
Climate Projections ◽  
Transfer Coefficients ◽  
Near Surface ◽  
Stability Functions ◽  
Stable Surface Layer ◽  
Heat And Moisture ◽  
The Impact

<p><span>Results of weather forecast, present-day climate simulations and future climate projections depend among other factors on the interaction between the atmosphere and the underlying sea-ice, the land and the ocean. In numerical weather prediction and climate models some of these interactions are accounted for by transport coefficients describing turbulent exchange of momentum, heat and moisture. Currently used transfer coefficients have, however, large uncertainties in flow regimes being typical for cold nights and seasons, but especially in the polar regions. Furthermore, their determination is numerically complex. It is obvious that progress could be achieved when the transfer coefficients would be given by simple mathematical formulae in frames of an economic computational scheme. Such a new universal, so-called non-iterative parametrization scheme is derived for a package of transfer coefficients.</span></p><p><span>The derivation is based on the Monin-Obukhov similarity theory, which is over the years well accepted in the scientific community. The newly derived non-iterative scheme provides a basis for a cheap systematic study of the impact of near-surface turbulence and of the related transports of momentum, heat and moisture in NWP and climate models. </span></p><p><span>We show that often used transfer coefficients like those of Louis et al. (1982) or of Cheng and Brutsaert (2005) can be applied at large stability only with some caution, keeping in mind that at large stability they significantly overestimate the transfer coefficient compared with most comprehensive measurements. The latter are best reproduced by Gryanik et al. (2020) functions, which are part of the package. We show that the new scheme is flexible, thus, new stability functions can be added to the package, if required. </span></p><p> </p><p> <span>Gryanik, V.M., Lüpkes, C., Grachev, A., Sidorenko, D. (2020) New Modified and Extended Stability Functions for the Stable Boundary Layer based on SHEBA and Parametrizations of Bulk Transfer Coefficients for Climate Models, J. Atmos. Sci., 77, 2687-2716</span></p><p><br><br></p>

scholarly journals Effects of Topside Structures and Wind Profile on Wind Tunnel Testing of FPSO Vessel Models

2020 ◽  
Vol 8 (6) ◽  
pp. 422
Author(s):  
Seungho Lee ◽  
Sanghun Lee ◽  
Soon-Duck Kwon
Keyword(s):  
Wind Tunnel ◽  
Operating Mode ◽  
Wind Loads ◽  
Wind Tunnel Testing ◽  
Wind Speeds ◽  
Medium Level ◽  
Wind Profiles ◽  
The Impact ◽  
Gantry Cranes ◽  
Tunnel Testing

This study examined the effects of wind loads on a floating production storage and offloading (FPSO) vessel, focusing in particular on the impact of the turbulent wind profiles, the level of details of the topside structures, and the operation modes of the gantry cranes. A series of wind tunnel tests were performed on the FPSO vessel model, developed with a scale of 1:200. It was observed that the wind loads measured using a low-detail model were often greater than those measured using a high-detail model. The measured wind loads corresponding to the Norwegian Maritime Directorate (NMD) profile with an exponent of 0.14, were approximately 19% greater than those corresponding to the Frøya profile in the entire range of wind directions, because of the slightly higher mean wind speeds of the NMD profile. The wind forces increased by up to 8.6% when the cranes were at operating mode compared to when they were at parking mode. In view of the observations made regarding the detail level of the tested models, a medium-level detail FPSO model can be considered adequate for the wind tunnel testing if a high-detail model is not available.

Wind-turning over the atmospheric boundary layer in observations and models

2020 ◽  
Author(s):  
Gunilla Svensson ◽  
Jenny Lindvall ◽  
Joakim Pyykkö
Keyword(s):  
Boundary Layer ◽  
Wind Speed ◽  
Climate Models ◽  
Similarity Theory ◽  
Rossby Number ◽  
Surface Drag ◽  
Turning Angle ◽  
Wind Speeds ◽  
The Vertical Distribution ◽  
Clear Increase

<p>As an attempt to find a way of evaluating the surface drag in global models, we have derived a climatology of the boundary-layer wind-turning angle over land (Lindvall and Svensson, 2019). It is based on radiosonde observations from 800 stations in the Integrated Global Radiosonde Archive (IGRA). The climatology and how the wind turning depend on a suite of parameters is analyzed. Results from previous studies indicating the importance of the planetary boundary layer (PBL) stratification for the angle of wind turning are confirmed. A clear increase in the wind-turning angle with wind speed, particularly for stratified conditions, is also evident. According to Rossby number similarity theory, the crossisobaric angle for a neutral and barotropic boundary layer decreases with the surface Rossby number, Ro. The IGRA observations indicate that this dependence on Ro might partly be linked to the dependence of the stratification on the wind speed, a dependence that seems to prevail even for the high wind speeds, a criterium that traditionally is used to approximate a neutral PBL. The vertical distribution of the turning of the wind is analyzed using the high resolution Stratospheric Processes And their Role in Climate (SPARC) data. For unstable cases, there is a maximum in the directional wind shear around the PBL top, whereas for the most stable class of cases there is a maximum near the surface. The midlatitude cross-isobaric mass transport is estimated using the IGRA data. The wind-turning angles from reanalysis fields and climate models are also presented, they generally underestimate the turning angle.</p>

scholarly journals The Influence of Swell on the Atmospheric Boundary Layer under Nonneutral Conditions

2018 ◽  
Vol 48 (4) ◽  
pp. 925-936 ◽  
Author(s):  
Zhongshui Zou ◽  
Dongliang Zhao ◽  
Jun A. Zhang ◽  
Shuiqing Li ◽  
Yinhe Cheng ◽  
...  
Keyword(s):  
Boundary Layer ◽  
Similarity Theory ◽  
Complex Problem ◽  
Wind Speeds ◽  
Stable Conditions ◽  
Turbulent Closure ◽  
Low Wind Speeds ◽  
Wind Profiles ◽  
Neutral Conditions ◽  
Wave Boundary

AbstractThe anomalous phenomena induced by the prevailing swell at low wind speeds prevent a complete understanding of air–sea interaction processes. Many studies have considered this complex problem, but most have focused on near-neutral conditions. In this study, the influence of the swell on the atmospheric boundary under nonneutral conditions was addressed by extending the turbulent closure models of Makin and Kudryavtsev and the Monin–Obukhov similarity theory (MOST; Monin and Yaglom) to the existence of swell and nonneutral conditions. It was shown that wind profiles derived from these models were consistent with each other and both departed from the traditional MOST. At low wind speeds, a supergeostrophic jet appeared on the upper edge of the wave boundary layer, which was also reported in earlier studies. Under nonneutral conditions, the influence of buoyancy was significant. The slope of the wind profile increased under stable conditions and became smoother under unstable conditions. Considering the effects of buoyancy and swell, the wind stress derived from the model agreed quantitatively with the observations.

scholarly journals ENSO in the Mid-Holocene according to CSM and HadCM3

2014 ◽  
Vol 27 (3) ◽  
pp. 1223-1242 ◽  
Author(s):  
William H. G. Roberts ◽  
David S. Battisti ◽  
Alexander W. Tudhope
Keyword(s):  
Wind Stress ◽  
Climate Models ◽  
Southern Oscillation ◽  
Spatiotemporal Variability ◽  
Bjerknes Feedback ◽  
Climate System Model ◽  
Ocean Atmosphere ◽  
The Mean ◽  
The Impact ◽  
Mean State

Abstract The offline linearized ocean–atmosphere model (LOAM), which was developed to quantify the impact of the climatological mean state on the variability of the El Niño–Southern Oscillation (ENSO), is used to illuminate why ENSO changed between the modern-day and early/mid-Holocene simulations in two climate modeling studies using the NCAR Climate System Model (CSM) and the Hadley Centre Coupled Model, version 3 (HadCM3). LOAM reproduces the spatiotemporal variability simulated by the climate models and shows both the reduction in the variance of ENSO and the changes in the spatial structure of the variance during the early/mid-Holocene. The mean state changes that are important in each model are different and, in both cases, are also different from those hypothesized to be important in the original papers describing these simulations. In the CSM simulations, the ENSO mode is stabilized by the mean cooling of the SST. This reduces atmospheric heating anomalies that in turn give smaller wind stress anomalies, thus weakening the Bjerknes feedback. Within the ocean, a change in the thermocline structure alters the spatial pattern of the variance, shifting the peak variance farther east, but does not reduce the overall amount of ENSO variance. In HadCM3, the ENSO mode is stabilized by a combination of a weaker thermocline and weakened horizontal surface currents. Both of these reduce the Bjerknes feedback by reducing the ocean’s SST response to wind stress forcing. This study demonstrates the importance of considering the combined effect of a mean state change on the coupled ocean–atmosphere system: conflicting and erroneous results are obtained for both models if only one model component is considered in isolation.

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