Relationship between Sea Surface Drag Coefficient and Wave State

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...

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Main Authors: Jian Shi, Zhihao Feng, Yuan Sun, Xueyan Zhang, Wenjing Zhang, Yi Yu
Format: Article
Language:English
Published: MDPI AG 2021-11-01
Series:Journal of Marine Science and Engineering
Subjects:
Online Access:https://www.mdpi.com/2077-1312/9/11/1248
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author Jian Shi
Zhihao Feng
Yuan Sun
Xueyan Zhang
Wenjing Zhang
Yi Yu
author_facet Jian Shi
Zhihao Feng
Yuan Sun
Xueyan Zhang
Wenjing Zhang
Yi Yu
author_sort Jian Shi
collection DOAJ
description 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 (<inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mrow><msub><mi>C</mi><mi>D</mi></msub></mrow></semantics></math></inline-formula>) does not increase linearly with the increasing wind speed, namely, the increase of <inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mrow><msub><mi>C</mi><mi>D</mi></msub></mrow></semantics></math></inline-formula> 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 <inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mrow><msub><mi>C</mi><mi>D</mi></msub></mrow></semantics></math></inline-formula> (<inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mrow><msub><mi>C</mi><mrow><mi>D</mi><mo>,</mo><mo> </mo><mi>e</mi><mi>f</mi><mi>f</mi></mrow></msub></mrow></semantics></math></inline-formula>) under strong winds. Our results indicate that wave age plays an important role in determining <inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mrow><msub><mi>C</mi><mi>D</mi></msub></mrow></semantics></math></inline-formula>. When the wave age is >0.4, <inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mrow><msub><mi>C</mi><mi>D</mi></msub></mrow></semantics></math></inline-formula> decreases with the wave age. However, when the wave age is ≤0.4, <inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mrow><msub><mi>C</mi><mi>D</mi></msub></mrow></semantics></math></inline-formula> increases with the wave age at low and moderate wind speeds but tends to decrease with the wave age at high wind speeds.
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spelling doaj.art-f048596a2e5549599deb96edf145eecc2023-11-22T23:53:57ZengMDPI AGJournal of Marine Science and Engineering2077-13122021-11-01911124810.3390/jmse9111248Relationship between Sea Surface Drag Coefficient and Wave StateJian Shi0Zhihao Feng1Yuan Sun2Xueyan Zhang3Wenjing Zhang4Yi Yu5College of Meteorology and Oceanography, National University of Defense Technology, Changsha 410073, ChinaCollege of Meteorology and Oceanography, National University of Defense Technology, Changsha 410073, ChinaCollege of Meteorology and Oceanography, National University of Defense Technology, Changsha 410073, ChinaCollege of Meteorology and Oceanography, National University of Defense Technology, Changsha 410073, ChinaCollege of Meteorology and Oceanography, National University of Defense Technology, Changsha 410073, ChinaCollege of Meteorology and Oceanography, National University of Defense Technology, Changsha 410073, ChinaThe 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 (<inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mrow><msub><mi>C</mi><mi>D</mi></msub></mrow></semantics></math></inline-formula>) does not increase linearly with the increasing wind speed, namely, the increase of <inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mrow><msub><mi>C</mi><mi>D</mi></msub></mrow></semantics></math></inline-formula> 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 <inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mrow><msub><mi>C</mi><mi>D</mi></msub></mrow></semantics></math></inline-formula> (<inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mrow><msub><mi>C</mi><mrow><mi>D</mi><mo>,</mo><mo> </mo><mi>e</mi><mi>f</mi><mi>f</mi></mrow></msub></mrow></semantics></math></inline-formula>) under strong winds. Our results indicate that wave age plays an important role in determining <inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mrow><msub><mi>C</mi><mi>D</mi></msub></mrow></semantics></math></inline-formula>. When the wave age is >0.4, <inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mrow><msub><mi>C</mi><mi>D</mi></msub></mrow></semantics></math></inline-formula> decreases with the wave age. However, when the wave age is ≤0.4, <inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mrow><msub><mi>C</mi><mi>D</mi></msub></mrow></semantics></math></inline-formula> increases with the wave age at low and moderate wind speeds but tends to decrease with the wave age at high wind speeds.https://www.mdpi.com/2077-1312/9/11/1248sea surface drag coefficientwave statewave agesea spray droplets
spellingShingle Jian Shi
Zhihao Feng
Yuan Sun
Xueyan Zhang
Wenjing Zhang
Yi Yu
Relationship between Sea Surface Drag Coefficient and Wave State
Journal of Marine Science and Engineering
sea surface drag coefficient
wave state
wave age
sea spray droplets
title Relationship between Sea Surface Drag Coefficient and Wave State
title_full Relationship between Sea Surface Drag Coefficient and Wave State
title_fullStr Relationship between Sea Surface Drag Coefficient and Wave State
title_full_unstemmed Relationship between Sea Surface Drag Coefficient and Wave State
title_short Relationship between Sea Surface Drag Coefficient and Wave State
title_sort relationship between sea surface drag coefficient and wave state
topic sea surface drag coefficient
wave state
wave age
sea spray droplets
url https://www.mdpi.com/2077-1312/9/11/1248
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AT wenjingzhang relationshipbetweenseasurfacedragcoefficientandwavestate
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