Estimating sea spray volume with a laser altimeter

2011 ◽  
pp. 110421064116041
Author(s):  
A. Toffoli ◽  
A. V. Babanin ◽  
M. A. Donelan ◽  
B. K. Haus ◽  
D. Jeong
Keyword(s):  
Sea Spray ◽  
Laser Altimeter ◽  
Spray Volume

scholarly journals A Wind–Wave-Dependent Sea Spray Volume Flux Model Based on Field Experiments

2021 ◽  
Vol 9 (11) ◽  
pp. 1168
Author(s):  
Xingkun Xu ◽  
Joey J. Voermans ◽  
Hongyu Ma ◽  
Changlong Guan ◽  
Alexander V. Babanin
Keyword(s):  
Field Experiments ◽  
Wind Wave ◽  
Weather Forecasting ◽  
Sea Spray ◽  
Volume Flux ◽  
Laser Altimeter ◽  
Flux Model ◽  
Spray Volume ◽  
Wave Properties

Sea spray can contribute significantly to the exchanges of heat and momentum across the air–sea interface. However, while critical, sea spray physics are typically not included in operational atmospheric and oceanic models due to large uncertainties in their parameterizations. In large part, this is because of the scarcity of in-situ sea spray observations which prevent rigorous validation of existing sea spray models. Moreover, while sea spray is critically produced through the fundamental interactions between wind and waves, traditionally, sea spray models are parameterized in terms of wind properties only. In this study, we present novel in-situ observations of sea spray derived from a laser altimeter through the adoption of the Beer–Lambert law. Observations of sea spray cover a broad range of wind and wave properties and are used to develop a wind–wave-dependent sea spray volume flux model. Improved performance of the model is observed when wave properties are included, in contrast to a parameterization based on wind properties alone. The novel in-situ sea spray observations and the predictive model derived here are consistent with the classic spray model in both trend and magnitude. Our model and novel observations provide opportunities to improve the prediction of air–sea fluxes in operational weather forecasting models.

Estimating Sea Spray Volume with a Laser Altimeter

2011 ◽  
Vol 28 (9) ◽  
pp. 1177-1183 ◽  
Author(s):  
A. Toffoli ◽  
A. V. Babanin ◽  
M. A. Donelan ◽  
B. K. Haus ◽  
D. Jeong
Keyword(s):  
Laser Radiation ◽  
Water Surface ◽  
Sea Spray ◽  
Average Intensity ◽  
Laser Altimeter ◽  
Indirect Measure ◽  
Simple Regression Model ◽  
Spray Droplets ◽  
Laser Altimeters ◽  
Spray Volume

Abstract Down-looking laser altimeters are commonly used to measure the sea surface elevation. However, because the laser radiation is attenuated by spray droplets suspended along the transmission path, it is presumed that altimeters may also provide an indirect measure of the sea spray volume. Here, this conjecture is discussed by means of laboratory experiments, which have been conducted in a wind-wave flume. A large number of wind conditions were considered between equivalent 10-m wind speeds of 20 and 60 m s−1 in order to generate different spray volumes above the water surface. The facility was equipped with a laser and side-looking camera system to estimate the spray volume as well as a nearby down-looking laser altimeter. Results confirm that there is a robust degradation of the laser intensity for increasing wind speed and hence the amount of spray droplets above the water surface. A simple regression model to extract spray volume from the average intensity of the laser radiation is presented, demonstrating the promise of laser altimeters for making in situ spray observations. Additional observations will be required to calibrate the altimeters for applications in the open ocean marine environment.

The estimation of sea spray at wind speeds ranging from light to extreme

2021 ◽  
Author(s):  
Xingkun Xu ◽  
Joey Voermans ◽  
Alexander Babanin ◽  
Hongyu Ma ◽  
Changlong Guan
Keyword(s):  
Laser Beam ◽  
Beam Intensity ◽  
Sea Spray ◽  
Wave Steepness ◽  
Volume Flux ◽  
Laser Beam Intensity ◽  
Infrared Laser Beam ◽  
Flux Model ◽  
The Mean ◽  
Spray Volume

<p>As one of typical elements in the air-sea boundary layer, sea spray is expected to mediate energy flux exchange in the air and ocean boundary layers, and therefore it is of crucial importance to the meteorology, oceanology, and regional climatology. In addition, the spray is also considered as one of the missing physical mechanisms in atmospheric and oceanic numerical models. Hence, it is necessary to accurately predict how much sea spray is produced at the air-sea boundary layer. Though spray has been studied for a number of decades, large uncertainties still linger. For instance, uncertainties in qualifying how much spray is produced on the sea surface reach 10<sup>6</sup> times. This is because of the rarity of spray observations in the field, especially under strong wind condition.</p><p>To give a reliable spray production model, scientists tried to employ laser-based facilities in the field to observe sea spray by interpreting infrared laser-beam intensity into sea spray volume flux over the water surface. Hence, in the current study, we collected datasets in the field measured by laser-based facilities on the North-West Shelf of the coast of Western Australia, thereafter, further analyzed, and calibrated them through a series of academic, statistical, and physical analysis to ensure the data quality. After that, assuming the existence of spray drops in the air-sea layer would attenuate the infrared laser-beam intensity, the weakening extends of laser-beam intensity is used to estimate the volume flux of sea spray above the ocean surface at winds speed ranging from light to extreme during the passage of Tropical Cyclone Olwyn (2015). It should be noted that our observations of sea spray volume flux are within the ranges of existing models and are consistent with the model proposed by Andreas (1992) in both trend and magnitude.</p><p>Using the field observations of the sea spray volume flux, a sea spray volume flux model can be constructed. Given that sea spray droplets are generated at the ocean surface through breaking waves and wind shear, the sea spray volume flux is expected to be dominated by the properties of the local wind and wave field. For physical consistency across the wide range of scales observed in the field and laboratory, non-dimensional parameters (i.e., non-dimensional wind speed and the mean wave steepness) were adopted to construct the model. Consequently, a power-law non-dimensional spray volumetric flux model is suggested based on the estimation of the spray volume flux. It should be noted that one sensitive test was conducted to substantiate the inclusion of wave breaking process, here simply included with the mean wave steepness, improves spray volume flux parameterization.</p>

The Andrea Wave Characteristics of a Measured North Sea Rogue Wave

2013 ◽  
Vol 135 (3) ◽  
Author(s):  
Anne Karin Magnusson ◽  
Mark A. Donelan
Keyword(s):  
North Sea ◽  
Rogue Wave ◽  
Order Theory ◽  
Second Order ◽  
Exceedance Probability ◽  
Sea Spray ◽  
Average Intensity ◽  
Laser Altimeter ◽  
The North ◽  
The One

Wave profiles have been measured with a system of four Optech lasers mounted on a bridge at the oil production site Ekofisk in the central North Sea since 2003, operated by ConocoPhillips. A double rogue wave was measured on Nov. 9, 2007 in a storm crossing the North Sea and named Andrea following a forecasting procedure between the Norwegian Meteorological Institute and ConocoPhillips. This wave, named here the “Andrea wave,” is comparable in height and characteristics to the well known Newyear wave (or Draupner wave) measured in 1995 by Statoil. Front steepness is higher. That the same profile is measured by all four lasers is a good indication that the shape of the wave has been captured correctly, but one may still ask if this crest is that of blue, green, or white water. That is, how much of the height is related to presence of foam or sea spray? We attempt to answer this using the information of intensity of the return signals, which has been related to wave breaking and sea spray in recent studies by Toffoli et al. (2011, “Estimating Sea Spray with a Laser Altimeter,” J. Atmos. Oceanic Technol., 28(9), pp. 1177–1183). Measurements of the average intensity of the return signal do not indicate presence of sea spray in the incoming part of the wave, but high intensity of return after the passage of the crest indicates presence of sea spray or foam on the parts of the waves exposed to winds. Cameras following the sea surface at measuring position with information on the return signal as given here would most probably increase our understanding of what is measured. Exceedance probability of crests and heights show a deviation from the second order distribution as given by Forristall (2000, “Wave Crests Distributions: Observations and Second-Order Theory,” J. Phys. Oceanogr. 30(8), pp. 1931–1943) for the one percent highest waves in an apparently stable 3 h period including the Andrea wave. The deviation already starts at crest/Hs factors around 1.0.

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.

Bulk Contributions Modulate the Sum-Frequency Generation Spectra of Interfacial Water on Model Sea-Spray Aerosols

2018 ◽  
Author(s):  
Sandeep K. Reddy ◽  
Raphael Thiraux ◽  
Bethany A. Wellen Rudd ◽  
Lu Lin ◽  
Tehseen Adel ◽  
...  
Keyword(s):  
Single Layer ◽  
Sum Frequency Generation ◽  
Second Order ◽  
Interfacial Structure ◽  
Sea Spray ◽  
Third Order ◽  
Systematic Analysis ◽  
Sum Frequency ◽  
Structure Of Water ◽  
Frequency Generation

Vibrational sum-frequency generation (vSFG) spectroscopy is used to determine the molecular structure of water at the interface of palmitic acid monolayers. Both measured and calculated spectra display speci c features due to third-order contributions to the vSFG response which are associated with nite interfacial electric potentials. We demonstrate that theoretical modeling enables to separate the third-order contributions, thus allowing for a systematic analysis of the strictly surface-sensitive, second-order component of the vSFG response. This study provides fundamental, molecular-level insights into the interfacial structure of water in a neutral surfactant system with relevance to single layer bio-membranes and environmentally relevant sea-spray aerosols. These results emphasize the key role that computer simulations can play in interpreting vSFG spectra and revealing microscopic details of water at complex interfaces, which can be difficult to extract from experiments due to the mixing of second-order, surface-sensitive and third-order, bulk-dependent contributions to the vSFG response.

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