Modeling of Reynolds Stress in the Non-Logarithmic Layer Generated under Strong Winds Affected Sea Surface

The coral reef ecosystem in Cu Lao Cham, Vietnam is part of the central zone of the Cu Lao Cham -Hoi An, a biosphere reserve and it is strictly protected. However, the impacts of natural disasters - tropical cyclones (TCs) go beyond human protection. The characteristic feature of TCs is strong winds and the consequences of strong winds are high waves. High waves caused by strong TCs (i.e. level 13 or more) cause decline in coral cover in the seas around Cu Lao Cham. Based on the relationship between sea surface temperature (SST) and the maximum potential intensity (MPI) of TCs, this research determines the number of strong TCs in Cu Lao Cham in the future. Using results from a regional climate change model, the risk is that the number of strong TCs in the period 2021-2060 under the RCP4.5 scenario, will be 3.7 times greater than in the period 1980-2019 and under the RCP 8.5 scenario it will be 5.2 times greater than in the period 1980-2019. We conclude that increases in SST in the context of climate change risks will increase the number and intensity of TCs and so the risk of their mechanical impact on coral reefs will be higher leading to degradation of this internationally important site.

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Relationship between Sea Surface Drag Coefficient and Wave State

Journal of Marine Science and Engineering ◽

10.3390/jmse9111248 ◽

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.

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The Study on a New Approximate Method of Computing Electromagnetic Scattering from Multilayer Rough Sea Surfaces

Applied Mechanics and Materials ◽

10.4028/www.scientific.net/amm.533.268 ◽

2014 ◽

Vol 533 ◽

pp. 268-273

Author(s):

Jia Sheng Tian ◽

Wan Pan ◽

Jian Shi

Keyword(s):

Electromagnetic Scattering ◽

Computation Time ◽

Sea Surface ◽

Analysis Method ◽

Large Matrix ◽

Random Rough Surfaces ◽

Strong Winds ◽

Rough Sea Surface ◽

Rough Sea ◽

Good Agreement

At high sea states strong winds make the sea surface broken, and become a multilayer-rough sea surface made of a large number of foams and droplets. Similarly, if the sea surface covered by oil and other dirts will also belong to the mutilayer rough sea surfaces of various medium properties. In this paper, applying the Kirchhoff Approximation (KA) and the electromagnetic theory of stratified media, electromagnetic scattering characteristics from a multilayer rough medium surface are calculated. Firstly, a detailed analysis of electromagnetic reflection from multilayer parallel interfaces under different incident angles is carried out. Secondly, combining the preceding two results and courses, electromagnetic scattering from the multilayer random rough surfaces is studied. The computed results are in good agreement with those by using the method of moments (MOM) and reported by some experts. Finally, the random rough sea surface covered by spilling oil or droplets and foams is calculated in detail. Compared with MOM, the new approximate analysis method in the paper can avoid a large matrix inversion, and thus greatly reduce the computation time and improve the computational efficiency.

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Analisis Kondisi Atmosfer Saat Kejadian Hujan Lebat dan Angin Kencang di Probolinggo Berdasarkan Citra Satelit dan Citra Radar

Jurnal Ilmu dan Inovasi Fisika ◽

10.24198/jiif.v5i2.31333 ◽

2021 ◽

Vol 5 (2) ◽

pp. 142-156

Author(s):

Nur Habib Muzaki ◽

Keyword(s):

Temperature Anomaly ◽

Remote Sensing Data ◽

Convective Cloud ◽

Heavy Rain ◽

Sea Surface ◽

Air Masses ◽

Sea Surface Temperature Anomaly ◽

Strong Winds ◽

Rain Events ◽

Spatial Maps

The phenomenon of extreme weather, heavy rain and strong winds hit four sub-districts in Probolinggo Regency, East Java on January 3, 2020 at 17.00 WIB. Based on data from the East Java Regional Disaster Management Agency (BPBD), the incidence of heavy rain and strong winds resulted in damage to as many as 204 houses. This study uses remote sensing data in the form of C-Band Radar and Himawari-8 Satellite and Copernicus ECMWF renalysis data. The data is processed into spatial maps and graphs which are then analyzed descriptively. The results of data analysis show that the reflectivity value reaches 43 dBZ and the wind speed reaches 13.57 m / s with a rainfall of 15.83 mm / hour at 10.00 WIB. Based on the analysis of the Himawari-8 Satellite, the peak temperature of the clouds reached -73.1 oC and the atmospheric lability data showed that the atmosphere was unstable, which could indicate the possibility of heavy rain and strong winds. The value of vortices in the 1000 mb - 500 mb layer is negative and the humidity value ranges from 85% - 90% and a positive sea surface temperature anomaly value and the presence of windshields result in convergence of air masses which can support convective cloud growth as the cause of heavy rain events and strong winds in Probolinggo Regency, East Java

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Predicting the Turbulent Air-Sea Surface Fluxes, Including Spray Effects, from Weak to Strong Winds

10.21236/ada598249 ◽

2013 ◽

Author(s):

Edgar L. Andreas ◽

Larry Mahrt

Keyword(s):

Surface Fluxes ◽

Sea Surface ◽

Strong Winds

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Atmospheric Mixed Layer Convergence from Observed MJO Sea Surface Temperature Anomalies

Journal of Climate ◽

10.1175/jcli-d-19-0351.1 ◽

2020 ◽

Vol 33 (2) ◽

pp. 547-558

Author(s):

Simon P. de Szoeke ◽

Eric D. Maloney

Keyword(s):

Surface Temperature ◽

Sea Surface Temperature ◽

Mixed Layer ◽

Deep Convection ◽

Equatorial Indian Ocean ◽

Sea Surface ◽

Planetary Rotation ◽

Atmospheric Mixed Layer ◽

Strong Winds ◽

The Right

ABSTRACTThe Madden–Julian oscillation (MJO) dominates tropical weather on intraseasonal 30–90-day time scales, yet mechanisms for its generation, maintenance, and propagation remain unclear. Although surface moist static energy (MSE) flux is greatest under strong winds in the convective phase, sea surface temperature (SST) warms by ~0.3°C in the clear nonconvective phase of the MJO. Winds converging into the hydrostatic low pressure under warm air over the warm SST increase the vertically integrated MSE. We estimate column-integrated MSE convergence using a model of mixed layer (ML) winds balancing friction, planetary rotation, and hydrostatic pressure gradients. Small (0.3 K) SST anomalies associated with the MJO drive 7 W m−2 net column MSE convergence averaged over the equatorial Indian Ocean ahead of MJO deep convection. The MSE convergence is in the right phase to contribute to MJO generation and propagation. It is on the order of the total MSE tendency previously assessed from reanalysis, and greater than surface heat flux anomalies driven by intraseasonal SST fluctuations.

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Cyclonic Wave Simulations Based on WAVEWATCH-III Using a Sea Surface Drag Coefficient Derived from CFOSAT SWIM Data

Atmosphere ◽

10.3390/atmos12121610 ◽

2021 ◽

Vol 12 (12) ◽

pp. 1610

Author(s):

Weizeng Shao ◽

Tao Jiang ◽

Yu Zhang ◽

Jian Shi ◽

Weili Wang

Keyword(s):

Drag Coefficient ◽

Numerical Models ◽

Sea Surface ◽

Surface Drag ◽

Wavewatch Iii ◽

Sea Surface Roughness ◽

Typhoon Wave ◽

Strong Winds ◽

Remote Sensing Techniques ◽

High Winds

It is well known that numerical models are powerful methods for wave simulation of typhoons, where the sea surface drag coefficient is sensitive to strong winds. With the development of remote sensing techniques, typhoon data (i.e., wind and waves) have been captured by optical and microwave satellites such as the Chinese-French Oceanography SATellite (CFOSAT). In particular, wind and wave spectra data can be simultaneously measured by the Surface Wave Investigation and Monitoring (SWIM) onboard CFOSAT. In this study, existing parameterizations for the drag coefficient are implemented for typhoon wave simulations using the WAVEWATCH-III (WW3) model. In particular, a parameterization of the drag coefficient derived from sea surface roughness is adopted by considering the terms for wave steepness and wave age from the measurements from SWIM products of CFOSAT from 20 typhoons during 2019–2020 at winds up to 30 m/s. The simulated significant wave height (Hs) from the WW3 model was validated against the observations from several moored buoys active during three typhoons, i.e., Typhoon Fung-wong (2014), Chan-hom (2015), and Lekima (2019). The analysis results indicated that the proposed parameterization of the drag coefficient significantly improved the accuracy of typhoon wave estimation (a 0.49 m root mean square error (RMSE) of Hs and a 0.35 scatter index (SI)), greater than the 0.55 RMSE of Hs and >0.4 SI using other existing parameterizations. In this sense, the adopted parameterization for the drag coefficient is recommended for typhoon wave simulations using the WW3 model, especially for sea states with Hs < 7 m. Moreover, the accuracy of simulated waves was not reduced with growing winds and sea states using the proposed parameterization. However, the applicability of the proposed parameterization in hurricanes necessitates further investigation at high winds (>30 m/s).

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Synchrony of trend shifts in Sahel summer rainfall and global oceanic evaporation, 1950–2012

Hydrology and Earth System Sciences Discussions ◽

10.5194/hessd-12-11269-2015 ◽

2015 ◽

Vol 12 (11) ◽

pp. 11269-11289

Author(s):

A. Diawara ◽

Y. Tachibana ◽

K. Oshima ◽

H. Nishikawa ◽

Y. Ando

Keyword(s):

Moisture Transport ◽

Summer Rainfall ◽

Sea Surface ◽

Positive Trend ◽

Atmospheric Moisture ◽

Opposite Trend ◽

Increasing Trend ◽

Strong Winds ◽

Subtropical Oceans ◽

Atmospheric Moisture Transport

Abstract. Between 1950 and 2012, summer (rainy season) rainfall in the Sahel changed from a multi-decadal decreasing trend to an increasing trend (positive trend shift) in the mid-1980s. We found that this trend shift was synchronous with similar trend shifts in global oceanic evaporation and in land precipitation in all continents except the Americas. The trend shift in oceanic evaporation occurred mainly in the Southern Hemisphere (SH) and the subtropical oceans of the Northern Hemisphere (NH). Because increased oceanic evaporation strengthens the atmospheric moisture transport toward land areas, the synchrony of oceanic evaporation and land precipitation is reasonable. Surface scalar winds over the SH oceans also displayed a positive trend shift. Sea surface temperature (SST) displayed a trend shift in the mid-1980s that was negative (increasing, then decreasing) in the SH and positive in the NH. Although SST had opposite trend shifts in both hemispheres, the trend shift in evaporation was positive in both hemispheres. We infer that because strong winds promote evaporative cooling, the trend shift in SH winds strengthened the trend shifts of both SST and evaporation in the SH. Because high SST promotes evaporation, the trend shift in NH SST strengthened the NH trend shift in evaporation. Thus differing oceanic roles in the SH and NH generated the positive trend shift in evaporation; however, the details of moisture transport toward the Sahel are still unclear.

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Nature's Carnot Engine: The Hurricane

Innovations in Engineering Education: Mechanical Engineering Education, Mechanical Engineering Technology Department Heads ◽

10.1115/imece2006-13359 ◽

2006 ◽

Author(s):

Maurice Bluestein

Keyword(s):

Constant Temperature ◽

Heat Engine ◽

Sea Surface ◽

Carnot Cycle ◽

Surface Boundary ◽

Surface Boundary Layer ◽

Conventional View ◽

Frictional Dissipation ◽

Strong Winds ◽

Temperature Work

The typical curriculum in a thermodynamics course includes the Carnot cycle, a series of processes that constitute the most efficient heat engine between two constant temperature reservoirs. The conventional view of this cycle is that it is an ideal that cannot be achieved in practice. The spate of hurricanes that battered the U.S. in 2005 has given rise to extensive thermodynamic analysis of these storms with the finding that they in fact replicate the Carnot cycle. Heat energy fuels the storm through evaporation of the warm ocean waters at constant temperature. Work is produced by adiabatic expansion upward of the saturated air, resulting in strong winds. Energy is then released by radiation to space at the approximately constant temperature of the upper atmosphere. Adiabatic compression follows as the air descends back to sea level. Unlike the textbook Carnot engine, the work output of the hurricane is returned to the cycle by frictional dissipation due to the wind at the sea surface boundary layer. This paper will describe the hurricane in thermodynamic terms so as to appreciate its great power and efficiency. It may be a worthwhile topic to include in a thermodynamics course.

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