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.

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

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.

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.

SPRAY DROPLET DISTRIBUTION AND HERBICIDE UPTAKE IN SEQUENTIAL APPLICATIONS OF DICLOFOP-METHYL AND MCPA FOR WEED CONTROL IN BARLEY

1979 ◽  
Vol 59 (1) ◽  
pp. 93-98 ◽  
Author(s):  
F. A. QURESHI ◽  
W. H. VANDEN BORN
Keyword(s):  
Acetic Acid ◽  
Leaf Surface ◽  
Avena Fatua ◽  
Wild Oat ◽  
Spray Application ◽  
Spray Droplet ◽  
Wild Oats ◽  
Droplet Distribution ◽  
Spray Droplets ◽  
Spray Volume

Uptake of 14C-diclofop-methyl {methyl 2-[4-(2,4-dichlorophenoxy)phenoxy propanoate]} by leaves of wild oats (Avena fatua L.) was reduced significantly in the presence of MCPA {[(4-chloro-o-tolyl)oxy]acetic acid]}, especially the dimethylamine formulation. If the herbicides were applied separately, the degree of interference with uptake depended on the extent of overlap of droplets of the two spray preparations on the leaf surface. Spray volume and direction of spray application were important factors in minimizing the mixing of spray droplets on the leaves if the two herbicides were applied separately with a tandem arrangement of two sprayers. Such a sequential application of MCPA ester and diclofop-methyl in a field experiment provided significantly greater wild oat control than could be obtained with a tank mix of the same two herbicides, but the results were not consistent enough to recommend the procedure for practical use.

Production rates of sea-spray droplets

1999 ◽  
Vol 104 (C8) ◽  
pp. 18397-18407 ◽  
Author(s):  
Martin J. Pattison ◽  
Stephen E. Belcher
Keyword(s):  
Sea Spray ◽  
Production Rates ◽  
Spray Droplets

scholarly journals Time constants for the evolution of sea spray droplets

Tellus B ◽  
1990 ◽  
Vol 42 (5) ◽  
pp. 481-497 ◽  
Author(s):  
Edgar L. Andreas
Keyword(s):  
Sea Spray ◽  
Time Constants ◽  
Spray Droplets

scholarly journals Improving maps of ice-sheet surface elevation change using combined laser altimeter and stereoscopic elevation model data

2013 ◽  
Vol 59 (215) ◽  
pp. 524-532 ◽  
Author(s):  
J.F. Levinsen ◽  
I.M. Howat ◽  
C.C. Tscherning
Keyword(s):  
Point Clouds ◽  
Altimeter Data ◽  
Laser Altimeter ◽  
Registration Errors ◽  
Digital Elevation ◽  
Surface Elevation Change ◽  
Laser Altimeters ◽  
Elevation Changes ◽  
Elevation Model ◽  
Spot 5

AbstractWe combine the complementary characteristics of laser altimeter data and stereoscopic digital elevation models (DEMs) to construct high-resolution (∼100 m) maps of surface elevations and elevation changes over rapidly changing outlet glaciers in Greenland. Measurements from spaceborne and airborne laser altimeters have relatively low errors but are spatially limited to the ground tracks, while DEMs have larger errors but provide spatially continuous surfaces. The principle of our method is to fit the DEM surface to the altimeter point clouds in time and space to minimize the DEM errors and use that surface to extrapolate elevations away from altimeter flight lines. This reduces the DEM registration errors and fills the gap between the altimeter paths. We use data from ICESat and ATM as well as SPOT 5 DEMs from 2007 and 2008 and apply them to the outlet glaciers Jakobshavn Isbræ (JI) and Kangerdlugssuaq (KL). We find that the main trunks of JI and KL lowered at rates of 30–35 and 7–20 m a−1,respectively. The rates decreased inland. The corresponding errors were 0.3–5.2 m a−1for JI and 0.3–5.1 m a−1for KL, with errors increasing proportionally with distance from the altimeter paths.

scholarly journals The Influence of the Speckle Structure of the Scattered Laser Radiation on the Measurement Error of the Rough Surface Vibration Displacement

2019 ◽  
Author(s):  
Илья Павлов ◽  
Il'ya Pavlov ◽  
Ирина Расковская ◽  
Irina Raskovskaya ◽  
Бронюс Ринкевичюс ◽  
...  
Keyword(s):  
Numerical Simulation ◽  
Laser Radiation ◽  
Measurement Error ◽  
Rough Surface ◽  
Laser Doppler Vibrometer ◽  
Average Intensity ◽  
Speckle Structure ◽  
Vibration Displacement ◽  
Speckle Field ◽  
Surface Vibration

The influence of the speckle structure of the scattered laser radiation on the measurement error of the rough surface vibration displacementusing laser Doppler vibrometer assembled according to a differential scheme is studied. The scheme of the experimental setup for investigation of characteristics of laser beam reflected from different surfaces is described and the obtaineed experimental images are given. It is shown that the structure of a reflected and scattered beam highly dependent on parameters of roughness of an investigated surface. Based on the results of numerical simulation, characteristic dimensions of surface irregularities are obtained, at which the beam structure is destroyed and the speckle structure is formed. It is shown that in case of a partially developed speckle structure, the error will be determined by by the relative contribution of a mirror component, a contrast and an average intensity of a speckle field. To estimate the error, a numerical simulation was performed for given parameters of a surface, beam and scatterers.

scholarly journals Генерация затопленной струи при лазерном нагреве поверхности жидкости

2020 ◽  
Vol 46 (20) ◽  
pp. 31
Author(s):  
В.М. Чудновский ◽  
В.И. Юсупов
Keyword(s):  
Laser Radiation ◽  
Optical Fiber ◽  
Opposite Direction ◽  
Water Surface ◽  
The Other ◽  
Jet Formation ◽  
Explosive Boiling ◽  
Cw Laser ◽  
Gas Cavity

It was found experimentally that when the water surface is heated by CW laser radiation through the optical fiber with a wavelength of 1.94 μm, jets are generated : one is submerged, directed inward liquid, the other directed in the opposite direction into the atmosphere. Jets are formed when the gas cavity collapses, arising in the process of explosive boiling of water caused by absorption of laser radiation directly under the fiber tip. The mechanism of jet formation is discussed.

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>

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