Bag-breakup spume droplet generation mechanism at high winds: Part II: The impact on momentum and enthalpy transfer

Yuliya Troitskaya, Oleg Druzhinin, D. Kozlov, Sergei Zilitinkevich

Forskningsoutput: TidskriftsbidragArtikelVetenskapligPeer review

Sammanfattning

In Part I of this study, we used high-speed video to identify bag breakup fragmentation as the dominant mechanism by which spume droplets are generated at gale-force and hurricane wind speeds. We also constructed a spray generation function (SGF) for the bag-breakup mechanism. The distinctive feature of this new SGF is the presence of giant (1000 m) droplets, which may significantly intensify the exchange between the atmosphere and the ocean. In this paper, Part II, we estimate the contribution of the bag-breakup mechanism to the momentum and enthalpy fluxes, which are known to strongly affect the development and maintenance of hurricanes. We consider three contributions to the spray-mediated aerodynamic drag: 1) bags as obstacles before fragmentation, 2) acceleration of droplets by the wind in the course of their production, and 3) stable stratification of the marine atmospheric boundary layer due to levitating droplets. Taking into account all of these contributions indicates a peaking dependence of the aerodynamic drag coefficient on the wind speed, which confirms the results of field and laboratory measurements. The contribution of the spray-mediated flux to the ocean-to-atmosphere moist enthalpy is also estimated using the concept of reentrant spray, and the equation for the enthalpy flux from a single droplet to the atmosphere is derived from microphysical equations. Our estimates show that a noticeable increase in the enthalpy exchange coefficient at winds exceeding 30-35 m s(-1) is due to the enhancement of the exchange processes caused by the presence of giant droplets originating from bag-breakup fragmentation.
Originalspråkengelska
TidskriftJournal of Physical Oceanography
Volym48
Utgåva9
Sidor (från-till)2189–2207
Antal sidor19
ISSN0022-3670
DOI
StatusPublicerad - sep 2018
MoE-publikationstypA1 Tidskriftsartikel-refererad

Vetenskapsgrenar

  • 114 Fysik
  • 1172 Miljövetenskap

Citera det här

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title = "Bag-breakup spume droplet generation mechanism at high winds: Part II: The impact on momentum and enthalpy transfer",
abstract = "In Part I of this study, we used high-speed video to identify bag breakup fragmentation as the dominant mechanism by which spume droplets are generated at gale-force and hurricane wind speeds. We also constructed a spray generation function (SGF) for the bag-breakup mechanism. The distinctive feature of this new SGF is the presence of giant (1000 m) droplets, which may significantly intensify the exchange between the atmosphere and the ocean. In this paper, Part II, we estimate the contribution of the bag-breakup mechanism to the momentum and enthalpy fluxes, which are known to strongly affect the development and maintenance of hurricanes. We consider three contributions to the spray-mediated aerodynamic drag: 1) bags as obstacles before fragmentation, 2) acceleration of droplets by the wind in the course of their production, and 3) stable stratification of the marine atmospheric boundary layer due to levitating droplets. Taking into account all of these contributions indicates a peaking dependence of the aerodynamic drag coefficient on the wind speed, which confirms the results of field and laboratory measurements. The contribution of the spray-mediated flux to the ocean-to-atmosphere moist enthalpy is also estimated using the concept of reentrant spray, and the equation for the enthalpy flux from a single droplet to the atmosphere is derived from microphysical equations. Our estimates show that a noticeable increase in the enthalpy exchange coefficient at winds exceeding 30-35 m s(-1) is due to the enhancement of the exchange processes caused by the presence of giant droplets originating from bag-breakup fragmentation.",
keywords = "114 Physical sciences, 1172 Environmental sciences",
author = "Yuliya Troitskaya and Oleg Druzhinin and D. Kozlov and Sergei Zilitinkevich",
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Bag-breakup spume droplet generation mechanism at high winds : Part II: The impact on momentum and enthalpy transfer. / Troitskaya, Yuliya; Druzhinin, Oleg; Kozlov, D.; Zilitinkevich, Sergei.

I: Journal of Physical Oceanography, Vol. 48, Nr. 9, 09.2018, s. 2189–2207.

Forskningsoutput: TidskriftsbidragArtikelVetenskapligPeer review

TY - JOUR

T1 - Bag-breakup spume droplet generation mechanism at high winds

T2 - Part II: The impact on momentum and enthalpy transfer

AU - Troitskaya, Yuliya

AU - Druzhinin, Oleg

AU - Kozlov, D.

AU - Zilitinkevich, Sergei

PY - 2018/9

Y1 - 2018/9

N2 - In Part I of this study, we used high-speed video to identify bag breakup fragmentation as the dominant mechanism by which spume droplets are generated at gale-force and hurricane wind speeds. We also constructed a spray generation function (SGF) for the bag-breakup mechanism. The distinctive feature of this new SGF is the presence of giant (1000 m) droplets, which may significantly intensify the exchange between the atmosphere and the ocean. In this paper, Part II, we estimate the contribution of the bag-breakup mechanism to the momentum and enthalpy fluxes, which are known to strongly affect the development and maintenance of hurricanes. We consider three contributions to the spray-mediated aerodynamic drag: 1) bags as obstacles before fragmentation, 2) acceleration of droplets by the wind in the course of their production, and 3) stable stratification of the marine atmospheric boundary layer due to levitating droplets. Taking into account all of these contributions indicates a peaking dependence of the aerodynamic drag coefficient on the wind speed, which confirms the results of field and laboratory measurements. The contribution of the spray-mediated flux to the ocean-to-atmosphere moist enthalpy is also estimated using the concept of reentrant spray, and the equation for the enthalpy flux from a single droplet to the atmosphere is derived from microphysical equations. Our estimates show that a noticeable increase in the enthalpy exchange coefficient at winds exceeding 30-35 m s(-1) is due to the enhancement of the exchange processes caused by the presence of giant droplets originating from bag-breakup fragmentation.

AB - In Part I of this study, we used high-speed video to identify bag breakup fragmentation as the dominant mechanism by which spume droplets are generated at gale-force and hurricane wind speeds. We also constructed a spray generation function (SGF) for the bag-breakup mechanism. The distinctive feature of this new SGF is the presence of giant (1000 m) droplets, which may significantly intensify the exchange between the atmosphere and the ocean. In this paper, Part II, we estimate the contribution of the bag-breakup mechanism to the momentum and enthalpy fluxes, which are known to strongly affect the development and maintenance of hurricanes. We consider three contributions to the spray-mediated aerodynamic drag: 1) bags as obstacles before fragmentation, 2) acceleration of droplets by the wind in the course of their production, and 3) stable stratification of the marine atmospheric boundary layer due to levitating droplets. Taking into account all of these contributions indicates a peaking dependence of the aerodynamic drag coefficient on the wind speed, which confirms the results of field and laboratory measurements. The contribution of the spray-mediated flux to the ocean-to-atmosphere moist enthalpy is also estimated using the concept of reentrant spray, and the equation for the enthalpy flux from a single droplet to the atmosphere is derived from microphysical equations. Our estimates show that a noticeable increase in the enthalpy exchange coefficient at winds exceeding 30-35 m s(-1) is due to the enhancement of the exchange processes caused by the presence of giant droplets originating from bag-breakup fragmentation.

KW - 114 Physical sciences

KW - 1172 Environmental sciences

U2 - 10.1175/JPO-D-17-0105.1

DO - 10.1175/JPO-D-17-0105.1

M3 - Article

VL - 48

SP - 2189

EP - 2207

JO - Journal of Physical Oceanography

JF - Journal of Physical Oceanography

SN - 0022-3670

IS - 9

ER -