Heat Fluxes, Whitecaps, and Sea Spray

Fairall, C. W.; Edson, James B.; Miller, Mary Ann

doi:10.1007/978-94-009-2069-9_6

Cited by 29 publications

(18 citation statements)

References 48 publications

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“…The range of normalized concentrations for the smaller particles is about 1.5 orders of magnitude for freshwater but is only 0.5 orders of magnitude for the saline water. This is consistent with the r À2 scaling of the normalized droplet evaporation rate, _ r/r, and with the fact that saline droplets do not completely evaporate but approach an equilibrium size on he basis of their salt content and the local relative humidity [Fairall et al, 1990]. The salinity effect also explains why the volume spectra for freshwater droplets are still increasing with size out to 0.8 mm radius while the saline droplets level off at about 0.1 mm radius.…”

Section: Droplet Concentration Profilessupporting

confidence: 80%

“…[7] In reasonably horizontally homogenous conditions, the aerosol particle conservation equation [Fairall et al, 1990] can be expressed…”

Section: Turbulent Transport Equationsmentioning

confidence: 99%

“…This situation can also be solved analytically [Fairall et al, 1990;Hoppel et al, 2002] but to a good approximation the vertical gradient of n becomes negligible just below the source, so the last two terms balance. Thus, we can write…”

Section: Simple Source and Profile Relationshipsmentioning

confidence: 99%

“…Because the source function cannot be measured directly at present, it is typically estimated from the height-dependent number size distribution of droplets, n(r, z) (see section 2). Current specifications of the source strength are based on laboratory studies, scaling arguments and a few field measurements at wind speeds less than 30 ms À1 [Fairall et al, 1990;Andreas, 1998;Kepert et al, 1999;Andreas and Emanuel, 2001]. Verification of droplet source parameterizations at high winds has been frustrated because of the difficulty of measuring n(r, z) and/or near-surface turbulent fluxes in hurricanes.…”

Section: Introductionmentioning

confidence: 99%

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Investigation of the physical scaling of sea spray spume droplet production

Fairall¹,

Banner²,

Peirson³

et al. 2009

J. Geophys. Res.

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105

129

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[1] In this paper we report on a laboratory study, the Spray Production and Dynamics Experiment (SPANDEX), conducted at the University of New South Wales Water Research Laboratory in Australia. The goals of SPANDEX were to illuminate physical aspects of spume droplet production and dispersion; verify theoretical simplifications used to estimate the source function from ambient droplet concentration measurements; and examine the relationship between the implied source strength and forcing parameters such as wind speed, surface turbulent stress, and wave properties. Observations of droplet profiles give reasonable confirmation of the basic power law profile relationship that is commonly used to relate droplet concentrations to the surface source strength. This essentially confirms that, even in a wind tunnel, there is a near balance between droplet production and removal by gravitational settling. The observations also indicate considerable droplet mass may be present for sizes larger than 1.5 mm diameter. Phase Doppler Anemometry observations revealed significant mean horizontal and vertical slip velocities that were larger closer to the surface. The magnitude seems too large to be an acceleration time scale effect. Scaling of the droplet production surface source strength proved to be difficult. The wind speed forcing varied only 23% and the stress increased a factor of 2.2. Yet, the source strength increased by about a factor of 7. We related this to an estimate of surface wave energy flux through calculations of the standard deviation of small-scale water surface disturbance, a wave-stress parameterization, and numerical wave model simulations. This energy index only increased by a factor of 2.3 with the wind forcing. Nonetheless, a graph of spray mass surface flux versus surface disturbance energy is quasi-linear with a substantial threshold.

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Section: Droplet Concentration Profilessupporting

confidence: 80%

“…[7] In reasonably horizontally homogenous conditions, the aerosol particle conservation equation [Fairall et al, 1990] can be expressed…”

Section: Turbulent Transport Equationsmentioning

confidence: 99%

Section: Simple Source and Profile Relationshipsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 2 more Smart Citations

Investigation of the physical scaling of sea spray spume droplet production

Fairall¹,

Banner²,

Peirson³

et al. 2009

J. Geophys. Res.

Self Cite

105

129

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show abstract

“…This term simulates the spume-droplet generation by the wind tearing off crests of breaking waves, and was used to investigate the spray-generation problem (Fairall et al 1990(Fairall et al , 2009K06;KM09). Droplets, being torn off from breaking waves, are injected into the airflow at the altitude of breaking waves crests, and since scales of breaking waves are different, the generation of droplets is spread over height.…”

Section: Mass and Momentum Conservationmentioning

confidence: 99%

Impact of Ocean Spray on the Dynamics of the Marine Atmospheric Boundary Layer

Kudryavtsev

Makin

2011

Boundary-Layer Meteorol

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The impact of ocean spray on the dynamics of the marine near-surface air boundary layer (MABL) in conditions of very high (hurricane) wind speeds is investigated. Toward this end, a model of the MABL in the presence of sea-spume droplets is developed. The model is based on the classical theory of the motion of suspended particles in a turbulent flow, where the mass concentration of droplets is not mandatory small. Description of the spume-droplet generation assumes that they, being torn off from breaking waves, are injected in the form of a jet of spray into the airflow at the altitude of breaking wave crests. The droplets affect the boundary-layer dynamics in two ways: via the direct impact of droplets on the airflow momentum forming the so-called spray force, and via the impact of droplets on the turbulent mixing through stratification. The latter is parametrized applying the Monin-Obukhov similarity theory. It is found that the dominant impact of droplets on the MABL dynamics appears through the action of the 'spray force' originated from the interaction of the 'rain of spray' with the wind velocity shear, while the efficiency of the stratification mechanism is weaker. The effect of spray leads to an increase in the wind velocity and suppression of the turbulent wind stress in the MABL. The key issue of the model is a proper description of the spume-droplet generation. It is shown that, after the spume-droplet generation is fitted to the observations, the MABL model is capable of reproducing the fundamental experimental finding-the suppression of the surface drag at very high wind speeds. We found that, at very high wind speeds, a thin part of the surface layer adjacent to the surface turns into regime of limited saturation with the spume droplets, resulting in the levelling off of the friction velocity and decrease of the drag coefficient as U −2 10 , U 10 being the wind speed at 10-m height.

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An observation of sea‐spray microphysics by airborne Doppler radar

Fairall

Pezoa

Moran

et al. 2014

Geophysical Research Letters

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This paper describes observations and analysis of Doppler radar data from a down-looking 94 GHz (W-Band) system operated from a NOAA WP-3 Orion research aircraft in Tropical Storm (TS) Karen. The flight took place on 5 October 2013; Karen had weakened with maximum winds around 20 m s À1 . Doppler spectral moments from the radar were processed to retrieve sea-spray microphysical properties (drop size and liquid water mass concentration) profiles in the height range 75-300 m above the sea surface. In the high wind speed regions of TS Karen (U 10 > 15 m s À1 ), sea spray was observed with a nominal mass-mode radius of about 40 μm, a radar-weighted gravitational fall velocity of about 1 m s À1 , and a mass concentration of about 10 À3 gm À3 at 75 m. Spray-drop mass concentration declined with height to values of about 10 À4 gm À3 at 300 m. Drop mass decreased slightly more slowly with increasing height than predicted by surface-layer similarity theory for a balance of turbulent diffusion vs fall velocity.

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Heat Fluxes, Whitecaps, and Sea Spray

Cited by 29 publications

References 48 publications

Investigation of the physical scaling of sea spray spume droplet production

Investigation of the physical scaling of sea spray spume droplet production

Impact of Ocean Spray on the Dynamics of the Marine Atmospheric Boundary Layer

An observation of sea‐spray microphysics by airborne Doppler radar

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