LATENT AND SENSIBLE HEAT COEFFICIENTS BASED ON DRAG COEFFICIENT AFFECTED BY WAVE AGE AND SEA SPRAY

2018 ◽  
Vol 74 (5) ◽  
pp. I_1201-I_1206
Author(s):  
Hiroki OKACHI ◽  
Tomohito J. YAMADA
Keyword(s):  
Drag Coefficient ◽  
Sea Spray ◽  
Wave Age ◽  
Sensible Heat

scholarly journals Relationship between Sea Surface Drag Coefficient and Wave State

2021 ◽  
Vol 9 (11) ◽  
pp. 1248
Author(s):  
Jian Shi ◽  
Zhihao Feng ◽  
Yuan Sun ◽  
Xueyan Zhang ◽  
Wenjing Zhang ◽  
...  
Keyword(s):  
Drag Coefficient ◽  
Momentum Flux ◽  
Sea Surface ◽  
Sea Spray ◽  
Wave Age ◽  
High Wind ◽  
Surface Drag ◽  
Wave State ◽  
Wind Speeds ◽  
Strong Winds

The sea surface drag coefficient plays an important role in momentum transmission between the atmosphere and the ocean, which is affected by ocean waves. The total air–sea momentum flux consists of effective momentum flux and sea spray momentum flux. Sea spray momentum flux involves sea surface drag, which is largely affected by the ocean wave state. Under strong winds, the sea surface drag coefficient (CD) does not increase linearly with the increasing wind speed, namely, the increase of CD is inhibited by strong winds. In this study, a sea surface drag coefficient is constructed that can be applied to the calculation of the air–sea momentum flux under high wind speed. The sea surface drag coefficient also considers the influence of wave state and sea spray droplets generated by wave breaking. Specially, the wave-dependent sea spray generation function is employed to calculate sea spray momentum flux. This facilitates the analysis not only on the sensitivity of the sea spray momentum flux to wave age, but also on the effect of wave state on the effective CD (CD, eff) under strong winds. Our results indicate that wave age plays an important role in determining CD. When the wave age is >0.4, CD decreases with the wave age. However, when the wave age is ≤0.4, CD increases with the wave age at low and moderate wind speeds but tends to decrease with the wave age at high wind speeds.

The impact of ocean waves on spray stress and surface drag coefficient

2019 ◽  
Vol 29 (2) ◽  
pp. 523-535
Author(s):  
Zhanhong Wan ◽  
Luping Li ◽  
Zhigen Wu ◽  
Jiawang Chen ◽  
Xiuyang Lü
Keyword(s):  
Drag Coefficient ◽  
Momentum Flux ◽  
Sea Surface ◽  
Sea Spray ◽  
Wave Age ◽  
Surface Drag ◽  
Content Type ◽  
Flux Formula ◽  
Hurricane Prediction ◽  
Windsea Reynolds Number

Purpose The behaviors of sea surface drag coefficient should be well understood for an accurate hurricane prediction. The speed of wind has been applied to characterize the spray production; however, this could result in inaccurate spray productions compared to the experimental or field data if the influence of wave state is not considered. This paper aims to integrate a new sea spray generation function, described by windsea Reynolds number, into the spray momentum flux formula to calculate the spray momentum. Design/methodology/approach On the basis of this spray momentum, this study proposes the new formulas of spray stress and drag coefficient when the wind speed is high. Findings Results of the revised formulas show that wave status had significant effects on the spray stress and sea surface drag coefficient. Also, wave age was found to be an important parameter that affects the drag coefficient. The drag coefficient decreased with the increasing wave age. Comparison between this study’s theoretical and observation values of drag coefficient shows that the study results are close to the measured values. Research limitations/implications The research findings can enhance the understanding of the behaviors of sea surface drag for an accurate hurricane prediction. Originality/value A new sea spray generation function, described by windsea Reynolds number, is integrated into the spray momentum flux formula to calculate the spray momentum. On the basis of this spray momentum, this study proposes the new formulas of spray stress and drag coefficient when the wind speed is high.

scholarly journals On the Linear Parameterization of Drag Coefficient over Sea Surface

2004 ◽  
Vol 34 (12) ◽  
pp. 2847-2851 ◽  
Author(s):  
Changlong Guan ◽  
Lian Xie
Keyword(s):  
Wind Speed ◽  
Drag Coefficient ◽  
Linear Function ◽  
Sea Surface ◽  
Wave Steepness ◽  
Wave Age ◽  
Age Dependent ◽  
Logarithmic Law ◽  
Linear Parameterization ◽  
Charnock Relation

Abstract Combining the logarithmic law with the Charnock relation yields a drag coefficient that is a function of wind speed with the Charnock coefficient as a parameter. It is found that the function is nearly linear within the typically measured range of the drag coefficient. The slope of the linear function is dominated by the Charnock coefficient. When the Charnock relation is extended to a wave age–dependent function, the drag coefficient remains a near-linear function of wind speed after invoking the 3/2 power law. The slope of the linear function is dominated by wave steepness.

Numerical simulation study of sea spray’s effect on tropical cyclone——a case study of typhoon “Megi”

2021 ◽  
Author(s):  
Jialin Zhang ◽  
Wenqing Zhang ◽  
Haofeng Xia ◽  
Changlong Guan
Keyword(s):  
Numerical Simulation ◽  
Heat Flux ◽  
Tropical Cyclone ◽  
Latent Heat ◽  
Latent Heat Flux ◽  
Momentum Flux ◽  
Sensible Heat Flux ◽  
Sea Spray ◽  
Sensible Heat ◽  
Thermodynamic Effects

<p>Sea spray has important influence on the evolution of tropical cyclone. The influence of sea spray in the numerical simulation and prediction of tropical cyclones is not ignorable. In order to explore the kinetic and thermodynamic effects of sea spray on tropical cyclone, the drag coefficient C<sub>D </sub>and the enthalpy transfer coefficient C<sub>K</sub> with sea spray’s effects were included in the coupled ocean-atmosphere-wave-sediment transport modeling system (COAWST). The numerical results show that, the effect of sea spray can effectively improve the simulation results of tropical cyclone path. When only the kinetic effect of sea spray is considered, the momentum flux at the surface of sea is little affected, and the upward sensible heat flux and latent heat flux are slightly increased. When kinetic and thermodynamic effects of sea spray is considered at the same time, the momentum flux is slightly increased, the upward sensible heat flux is increased, and the latent heat flux is significantly increased, the intensity of tropical cyclone is significantly enhanced, mainly due to the thermodynamic effect . Considering the kinetic and thermodynamic effects of sea spray at the same time is more effective than considering the kinetic effects of sea spray in improving the intensity simulation of tropical cyclone.</p>

Impact of Sea Spray on Air–Sea Fluxes. Part II: Feedback Effects

2014 ◽  
Vol 44 (11) ◽  
pp. 2835-2853 ◽  
Author(s):  
James A. Mueller ◽  
Fabrice Veron
Keyword(s):  
Wind Speed ◽  
Drag Coefficient ◽  
Size Distribution ◽  
Water Mass ◽  
Stochastic Simulations ◽  
Sea Spray ◽  
Feedback Effects ◽  
Wind Speeds ◽  
Feedback Model ◽  
Rate Of Increase

Abstract This paper presents estimations for the transfer of momentum, heat, and water mass between the air and the sea. The results from Lagrangian stochastic simulations of sea spray drops (see Part I), along with two sea spray generation functions, are used to calculate the spray-mediated flux components of the air–sea fluxes. When the spray-mediated fluxes constitute a significant fraction of the total fluxes under certain conditions, their feedback effect on the atmosphere cannot be neglected. The authors derive a simplified feedback model to investigate such cases, finding that the spray-mediated fluxes may be especially sensitive to the size distribution of the drops. The total effective air–sea fluxes lead to drag and enthalpy coefficients that increase modestly with wind speed. The rate of increase for the drag coefficient is greatest at moderate wind speeds, while the rate of increase for the enthalpy coefficient is greatest at higher wind speeds where the spray is ubiquitous.

scholarly journals Contributions of Surface Sensible Heat Fluxes to Tropical Cyclone. Part II: The Sea Spray Processes

2015 ◽  
Vol 72 (11) ◽  
pp. 4218-4236 ◽  
Author(s):  
Zhanhong Ma ◽  
Jianfang Fei ◽  
Xiaoping Cheng ◽  
Yuqing Wang ◽  
Xiaogang Huang
Keyword(s):  
Latent Heat ◽  
Thermal Effects ◽  
Potential Temperature ◽  
Heat Fluxes ◽  
Sea Spray ◽  
Sensible Heat ◽  
Equivalent Potential ◽  
Moisture Effects ◽  
Spray Droplets ◽  
Surface Enthalpy

Abstract In Part II of this study, the roles of surface sensible heat fluxes (SHX) in tropical cyclones (TCs) are further investigated in the context of sea spray processes. Results show that the sea spray evaporation is favorable for the TC intensification through enhancing the surface latent heat fluxes (LHX). Unlike the results in Part I, the removal of SHX has led to a somewhat weaker TC by inclusion of sea spray. This is because the spray-mediated latent heat fluxes are simultaneously diminished after cutting down the SHX. Without the warming of SHX from the ocean, the surface air becomes cooler and thereby closer to saturation, which substantially hinders the evaporation of sea spray droplets. Therefore, the SHX are instrumental for sustaining the release of latent heat fluxes by sea spray evaporation. In the experiments of Part I and this study, the reduced total surface enthalpy fluxes as a result of the removal of SHX do not necessarily result in weakened TCs, while the larger LHX basically correspond to stronger TCs. This suggests that the TC intensity is largely dependent on the LHX rather than the total surface enthalpy fluxes, although the latter is generally dominated by the former. Relative roles of thermal and moisture effects in radially elevating the surface equivalent potential temperature θe are also compared. The contributions of thermal effects account for 30%–35% of the total changes in θe for mature TCs, no matter whether SHX from the ocean are included. This further implies that the SHX contribute insignificantly to the spinup of a TC.

The Influence of wave state and sea spray on drag coefficient from low to high wind speeds

2016 ◽  
Vol 15 (1) ◽  
pp. 41-49 ◽  
Author(s):  
Jian Shi ◽  
Zhong Zhong ◽  
Xunqiang Li ◽  
Guorong Jiang ◽  
Wenhua Zeng ◽  
...  
Keyword(s):  
Drag Coefficient ◽  
Sea Spray ◽  
High Wind ◽  
Wave State ◽  
Wind Speeds

Investigation of sea spray effect on the vertical momentum transport using an Eulerian multi-fluid-type model

2021 ◽  
Author(s):  
Yevgenii Rastigejev ◽  
Sergey A. Suslov
Keyword(s):  
Drag Coefficient ◽  
Reference Values ◽  
Volume Fraction ◽  
Momentum Transport ◽  
Sea Spray ◽  
Type Model ◽  
Wind Condition ◽  
Free Atmosphere ◽  
Turbulence Suppression ◽  
Spray Volume

AbstractThe Eulerian multi-fluid mathematical model is developed to describe the marine atmospheric boundary layer laden with sea spray under high wind condition of a hurricane. The model considers spray and air as separate continuous interacting turbulent media and employs the multi-fluid E – ε closure. Each phase is described by its own set of coupled conservation equations and characterized by its own velocity. Such an approach enables us to accurately quantify the interaction between spray and air and pinpoint the effect of spray on the vertical momentum transport much more precisely than could be done with traditional mixture-type approaches. The model consistently quantifies the effect of spray inertia and the suppression of air turbulence due to two different mechanisms: the turbulence attenuation, which results from the inability of spray droplets to fully follow turbulent fluctuations, and the vertical transport of spray against the gravity by turbulent eddies. The results of numerical and asymptotic analyses show that the turbulence suppression by spray overpowers its inertia several meters above wave crests resulting in a noticeable wind acceleration and the corresponding reduction of the drag coefficient from the reference values for a spray-free atmosphere. This occurs at a much lower than predicted previously spray volume fraction values ~ 10−5. The falloff of the drag coefficient from its reference values is stronger pronounced at higher altitudes. The drag coefficient reaches its maximum at spray volume fraction values ~ 10−4 that is several times smaller than predicted by mixture-type models.

scholarly journals Boundary layer characteristics associated with sea breeze circulation over Cochin

MAUSAM ◽  
2021 ◽  
Vol 58 (1) ◽  
pp. 75-86
Author(s):  
HAMZA V ◽  
C. A. BABU
Keyword(s):  
Boundary Layer ◽  
Heat Flux ◽  
Drag Coefficient ◽  
Momentum Flux ◽  
Sensible Heat Flux ◽  
Sea Breeze ◽  
Surface Fluxes ◽  
Land Breeze ◽  
Sensible Heat ◽  
Breeze Circulation

Features of sea and land breezes, surface fluxes and drag coefficient over Cochin are studied using more than 300 daily observations of air temperature, wind speed and direction data. The duration and intensity of sea breeze circulation vary with the rain or cloud as it reduces the differential heating. Onset of sea breeze is early in summer season for the near equatorial station compared to winter season. Cessation is almost same for all seasons and is around 1900 hours. The sea breeze circulation is almost westerly and land breeze circulation is almost easterly in all the seasons. It is found that in most of the cases, the temperature and wind speed decreases at the time of onset of sea breeze and turning of wind direction with height becomes counter clockwise (backing) during the transition period from land breeze to sea breeze. In all seasons, the momentum flux is directed downward. High values of momentum flux were found during the presence of sea breeze in pre-monsoon season. Average sensible heat flux is directed upward during the entire period and during nighttime it is almost zero in the winter and monsoon seasons. The intensity of momentum flux decreases during onset and cessation of sea breeze for all the cases. The cold air advection associated with the sea breeze results in the decrease of sensible heat flux at the time of onset of sea breeze. Averaged surface momentum and sensible flux patterns resemble closely to the instantaneous pattern for all the seasons. Generally, sea breeze is stronger than land breeze in all the seasons. Accordingly, the drag coefficient power relationship with wind is different for sea breeze and land breeze circulations.Key words – Sea breeze circulation, Monsoon boundary layer, Surface fluxes, Drag coefficient, Diurnal variation.

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