Modelling sensible and latent heat fluxes over sea during unstable, very close to neutral conditions

Rutgersson, Anna; Carlsson, Björn; Smedman, Ann‐Sofi

doi:10.1007/s10546-006-9150-9

Cited by 7 publications

(12 citation statements)

References 26 publications

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“…This study also uses phase speed and direction of dominant waves from the same data set, calculated using the WAM model (WAMDI Group, 1988). Surface‐layer relationships according to MOST are used below the lowest model level at 90 m above mean sea level to calculate the wind speed at 10 m and temperature and specific humidity at 2 m. The turbulent fluxes are calculated according to Woetmann‐Nielsen (1998), with some minor changes (see appendix B and ) in Rutgersson et al, 2007). The roughness length in the original version of the RCA model is described by where α is set to 0.014 and 0.032 over open and coastal water, respectively, and f is a wind speed weighting function for the transition between smooth and rough flow.…”

Section: Measurements and Modelmentioning

confidence: 99%

Impact of swell on simulations using a regional atmospheric climate model

Carlsson

Rutgersson

Smedman

2009

Tellus A: Dynamic Meteorology and Oceanography

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A B S T R A C T When long, fast swell waves travel in approximately the same direction as the wind, the surface stress is reduced compared with under wind-sea conditions. Using measurements from theÖstergarnsholm site in the Baltic Sea, new expressions of the roughness length were developed for wind sea and swell. These new expressions were implemented in the RCA3 regional climate model covering Europe. A 3-year simulation and two case studies using the wavefield from the ECMWF reanalysis (ERA-40) were analysed using the improved formulations. Wind-following swell led to a significant reduction of mean wind stress and heat fluxes. The mean surface layer wind speed was redistributed horizontally and the marine boundary layer cooled and dried slightly. This cooling was most pronounced over North Sea and the Norwegian Sea (almost 0.2 • C annually on average) whereas the drying was most pronounced over the Mediterranean Sea (almost 0.4 g kg −1 ). Somewhat less convective precipitation and low-level cloudiness over the sea areas were also indicated, in particular over the Mediterranean Sea. The impact on the atmosphere, however, is significantly locally greater in time and space.

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Section: Measurements and Modelmentioning

confidence: 99%

Impact of swell on simulations using a regional atmospheric climate model

Carlsson

Rutgersson

Smedman

2009

Tellus A: Dynamic Meteorology and Oceanography

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“…0:1 K. Peak values of the enhancement factors, at the highest wind speeds and least unstable conditions are similar, although the formulas of Rutgersson et al (2007) show greater enhancement for stronger temperature contrasts. 1 It is important to note that the enhancement factor derived above is a theoretically based one for a single process, whereas the enhancement factor of Rutgersson et al (2007) was derived observationally and may be influenced by several processes. Nevertheless, we suggest that some of the enhancement observed by Rutgersson et al (2007) should be explained by frictional dissipative heating.…”

Section: Basic Theory In Nearly Neutral Conditionsmentioning

confidence: 75%

“…We may term the ratio C 0 H /C H an enhancement factor. Likewise, an enhancement factor for the UVCN regime of Rutgersson et al (2007) may be derived from their Eqs. (8) and (10).…”

Section: Basic Theory In Nearly Neutral Conditionsmentioning

confidence: 99%

“…1 It is important to note that the enhancement factor derived above is a theoretically based one for a single process, whereas the enhancement factor of Rutgersson et al (2007) was derived observationally and may be influenced by several processes. Nevertheless, we suggest that some of the enhancement observed by Rutgersson et al (2007) should be explained by frictional dissipative heating. Conversely, it should be noted that dissipative heating provides no mechanism to enhancement of the latent heat flux that is also reported by Rutgersson et al (2007).…”

Section: Basic Theory In Nearly Neutral Conditionsmentioning

confidence: 99%

“…They propose that a distinct regime of thermodynamic stability should be recognized to encompass such cases, for which they propose the term ''unstable very close to neutral'' (UVCN). Subsequent modeling studies (Rutgersson et al 2007;Sahlée et al 2008) have suggested that these effects may be important in storms and, on annual time scales, in the surface flux budget of regions of consistently high wind speeds, such as the Southern Ocean.…”

Section: Introductionmentioning

confidence: 99%

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Sensible Heat Fluxes in the Nearly Neutral Boundary Layer: The Impact of Frictional Heating within the Surface Layer

Edwards

2019

Journal of the Atmospheric Sciences

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The effect of frictional dissipative heating on the calculation of surface fluxes in the atmospheric boundary layer using bulk flux formulas is considered. Although the importance of frictional dissipation in intense storms has been widely recognized, it is suggested here that its impact is also to be seen at more moderate wind speeds in apparently enhanced heat transfer coefficients and countergradient fluxes in nearly neutral conditions. A simple modification to the bulk flux formula can be made to account for its impact within the surface layer. This modification is consistent with an interpretation of the surface layer as one across which the flux of total energy is constant. The effect of this modification on tropical cyclones is assessed in an idealized model, where it is shown to reduce the predicted maximum wind speed by about 4%. In numerical simulations of three individual storms, the impacts are more subtle but indicate a reduction of the sensible heat flux into the storm and a cooling of the surface layer.

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Air‐Sea Heat and Momentum Fluxes in the Southern Ocean

Bharti

Fairall²,

Blomquist³

et al. 2019

JGR Atmospheres

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The Clouds, Aerosols, Precipitation, Radiation, and atmospherIc Composition Over the southeRn oceaN (CAPRICORN) experiment was carried out in March–April 2016 onboard R/V Investigator studying momentum (τ), sensible heat (Hs), and latent heat (Hl) fluxes over the Australian sector of the Southern Ocean including over one cyclonic cold‐core and one anticyclonic warm‐core mesoscale oceanic eddy. The turbulence‐based flux measurements obtained with the NOAA PSD flux system employing eddy covariance (EC) and inertial dissipation (ID) methods are compared with those obtained by the Coupled Ocean‐Atmosphere Response Experiment (COARE) 3.5 bulk model, and the neutral transfer coefficients are studied. The relative uncertainty between the turbulence‐based and COARE 3.5 estimates of τ, Hs, and Hl are 22%, 70%, and 26%, respectively, at 1‐hr time scale over the Southern Ocean. Further, the variability in bulk fluxes is investigated with respect to oceanic eddies, precipitation events, atmospheric stability, and extratropical cyclones encountered during the voyage. The main observed variability is an increase in significant wave height or γw (∼33%), τ (∼89%), Hs (∼187%), and Hl (∼79%) over the warm eddy as compared to average voyage values. During the passage of six extratropical cyclones, an increase in τ (∼62% average) and a decrease in Hs (∼235%) and Hl (∼79%) is noted in the warm sector, compared to prestorm conditions, but the pattern reverses behind the cold front.

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Modelling sensible and latent heat fluxes over sea during unstable, very close to neutral conditions

Cited by 7 publications

References 26 publications

Impact of swell on simulations using a regional atmospheric climate model

Impact of swell on simulations using a regional atmospheric climate model

Sensible Heat Fluxes in the Nearly Neutral Boundary Layer: The Impact of Frictional Heating within the Surface Layer

Air‐Sea Heat and Momentum Fluxes in the Southern Ocean

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