A Review of Parameterizations for Enthalpy and Momentum Fluxes from Sea Spray in Tropical Cyclones

Sroka, Sydney; Emanuel, Kerry

doi:10.1175/jpo-d-21-0023.1

Cited by 21 publications

(19 citation statements)

References 117 publications

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“…As such, it has an indirect, rather than direct, influence on the air-sea momentum flux. In addition to indirect dynamic effects, sea spray also directly influences the air-sea momentum, such as by modulating the roughness length [40,41] and increasing/decreasing the net air-sea momentum fluxes [42]. While it is still under debate how the sea spray dynamically affects the air-sea interaction, spray droplets strongly mediate net air-sea momentum fluxes, accounting for up to 16% of the interfacial momentum fluxes [43].…”

Section: Impacts On the Tc Systemmentioning

confidence: 99%

Impacts of the Wave-Dependent Sea Spray Parameterizations on Air–Sea–Wave Coupled Modeling under an Idealized Tropical Cyclone

Voermans

Liu

et al. 2021

JMSE

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While sea spray can significantly impact air–sea heat fluxes, the effect of spray produced by the interaction of wind and waves is not explicitly addressed in current operational numerical models. In the present work, the thermal effects of the sea spray were investigated for an idealized tropical cyclone (TC) through the implementation of different sea spray models into a coupled air–sea–wave numerical system. Wave-Reynolds-dependent and wave-steepness-dependent sea spray models were applied to test the sensitivity of local wind, wave, and ocean fields of this TC system. Results show that while the sensible heat fluxes decreased by up to 231 W m−2 (364%) and 159 W m−2 (251%), the latent heat fluxes increased by up to 359 W m−2 (89%) and 263 W m−2 (76%) in the simulation period, respectively. This results in an increase of the total heat fluxes by up to 135 W m−2 (32%) and 123 W m−2 (30%), respectively. Based on different sea spray models, sea spray decreases the minimum sea level pressure by up to 7 hPa (0.7%) and 8 hPa (0.8%), the maximum wind speed increases by up to 6.1 m s−1 (20%) and 5.7 m s−1 (19%), the maximum significant wave height increases by up to 1.1 m (17%) and 1.6 m (25%), and the minimum sea surface temperature decreases by up to 0.2 °C (0.8%) and 0.15 °C (0.6%), respectively. As the spray has such significant impacts on atmospheric and oceanic environments, it needs to be included in TC forecasting models.

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Section: Impacts On the Tc Systemmentioning

confidence: 99%

Impacts of the Wave-Dependent Sea Spray Parameterizations on Air–Sea–Wave Coupled Modeling under an Idealized Tropical Cyclone

Voermans

Liu

et al. 2021

JMSE

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“…An accurate estimation of air-sea enthalpy and momentum fluxes is key to improving intensity forecast accuracy in numerical weather prediction models (Sroka and Emanuel, 2021). Whether C k /C d decreases or increases at extreme winds above 50 m s −1 remains debatable.…”

Section: Conclusion and Discussionmentioning

confidence: 99%

New parameterization of air-sea exchange coefficients and its impact on intensity prediction under major tropical cyclones

et al. 2022

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Understanding and quantifying air-sea exchanges of enthalpy and momentum fluxes are crucial for the advanced prediction of tropical cyclone (TC) intensity. Here, we present a new parameterization of air-sea fluxes at extreme wind speeds from 40 m s−1 to 75 m s−1, which covers the range of major TCs. Our approach assumes that the TC can reach its maximum potential intensity (MPI) if there are no influences of external forces such as vertical wind shear or other environmental constraints.This method can estimate the ratio of the enthalpy and momentum exchange coefficient (Ck/Cd) under the most intense TCs without direct flux measurements. The estimation showed that Ck/Cd increases with wind speed at extreme winds above 40 m s−1. Two types of surface layer schemes of the Hurricane Weather and Research Forecast (HWRF) were designed based on the wind speed dependency of the Ck/Cd found at high winds: (i) an increase of Ck/Cd based on decreasing Cd (Cd_DC) and (ii) an increase of Ck/Cd based on increasing Ck (Ck_IC). The modified surface layer schemes were compared to the original HWRF scheme (using nearly fixed Cd and Ck at extreme winds; CTRL) through idealized experiments and real-case predictions. The idealized experiments showed that Cd_DC reduced frictional dissipation in the air-sea interface as well as significantly reduced sea surface cooling, making the TC stronger than other schemes. As a result, Cd_DC reduced the mean absolute error and negative bias by 15.0% (21.0%) and 19.1% (32.0%), respectively, for all lead times of Hurricane Irma in 2017 (Typhoon Mangkhut in 2018) compared to CTRL. This result suggests that new parameterization of Ck/Cd with decreasing Cd at high winds can help improve TC intensity prediction, which currently suffers from underestimating the intensity of the strongest TCs.

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“…One factor in particular that is central to our understanding of the transfer of heat and momentum at high wind speeds is the presence of spray droplets. Spray mediation of air-sea fluxes has been the subject of many previous investigations, including theoretical, observational, and numerical modeling approaches, and a comprehensive review on the subject can be found in Veron (2015) or Sroka and Emanuel (2021). Although many numerical modeling studies have investigated the impact of spray on air-sea fluxes, most of these studies have relied on bulk estimates in which the net effect of spray is parameterized rather than handled explicitly.Here we investigate the impact of sea spray on the transfer coefficients for momentum, heat, and moisture, by performing simulations using a large-eddy simulation (LES) code coupled with a Lagrangian microphysical model.…”

mentioning

confidence: 99%

“…Further complications arise from a lack of knowledge on how the presence of sea spray affects the air-sea fluxes, and how this varies with wind speed (Veron, 2015). Improving parameterizations of air-sea fluxes in numerical models is of particular importance for reducing uncertainty in intensity forecasts (Sroka & Emanuel, 2021).…”

mentioning

confidence: 99%

Large‐Eddy Simulation of Sea Spray Impacts on Fluxes in the High‐Wind Boundary Layer

Richter

Wainwright

2023

Geophysical Research Letters

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Although there have been considerable improvements in forecasting the track of tropical cyclones (TCs) over the past several decades, intensity forecasts remain challenging and improvements have lagged behind (Rogers et al., 2006). One challenge is that the understanding of air-sea exchange in high-wind regimes remains limited due to the logistical difficulty of taking measurements in these conditions. Further complications arise from a lack of knowledge on how the presence of sea spray affects the air-sea fluxes, and how this varies with wind speed (Veron, 2015). Improving parameterizations of air-sea fluxes in numerical models is of particular importance for reducing uncertainty in intensity forecasts (Sroka & Emanuel, 2021).Key parameters in air-sea exchange are the surface drag coefficient (C D ) and surface enthalpy flux coefficient (C K ), which are known to factor into the maximum storm potential energy and the maximum tangential wind speed (Emanuel, 1995). In numerical weather prediction (NWP) models C D and C K (or the individual heat and moisture coefficients, C H and C E , often assumed to be equal to C K ) are typically parameterized as functions of the 10-m wind speed (U 10 ). At high winds beyond roughly 30 ms −1 , however, the behavior of these flux coefficients are highly uncertain (Richter et al., 2016), and almost certainly not solely a function of wind speed. One factor in particular that is central to our understanding of the transfer of heat and momentum at high wind speeds is the presence of spray droplets. Spray mediation of air-sea fluxes has been the subject of many previous investigations, including theoretical, observational, and numerical modeling approaches, and a comprehensive review on the subject can be found in Veron (2015) or Sroka and Emanuel (2021). Although many numerical modeling studies have investigated the impact of spray on air-sea fluxes, most of these studies have relied on bulk estimates in which the net effect of spray is parameterized rather than handled explicitly.Here we investigate the impact of sea spray on the transfer coefficients for momentum, heat, and moisture, by performing simulations using a large-eddy simulation (LES) code coupled with a Lagrangian microphysical model. Paired simulations are performed with and without the presence of spray, across a range of wind speeds up

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A Review of Parameterizations for Enthalpy and Momentum Fluxes from Sea Spray in Tropical Cyclones

Cited by 21 publications

References 117 publications

Impacts of the Wave-Dependent Sea Spray Parameterizations on Air–Sea–Wave Coupled Modeling under an Idealized Tropical Cyclone

Impacts of the Wave-Dependent Sea Spray Parameterizations on Air–Sea–Wave Coupled Modeling under an Idealized Tropical Cyclone

New parameterization of air-sea exchange coefficients and its impact on intensity prediction under major tropical cyclones

Large‐Eddy Simulation of Sea Spray Impacts on Fluxes in the High‐Wind Boundary Layer

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