Surface stress in offshore flow and quasi‐frictional decoupling

Mahrt, L.; Vickers, Dean; Sun, Jielun; Crawford, Timothy L.; Crescenti, Gennaro H.; Frederickson, Paul A.

doi:10.1029/2000jd000159

Cited by 23 publications

(17 citation statements)

References 32 publications

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“…In that study, aircraft data show that for flow from warm to cold water, the winds close to the surface decelerate over the cold water and may decouple from the large-scale flow aloft, forming a separate, internal boundary layer (IBL). Similar decoupling events have been reported in Smedman et al (1997) and Mahrt et al (2001), with the IBL persisting for hundreds of km downwind from the SST transition.…”

Section: Introductionsupporting

confidence: 83%

Effects of mesoscale sea-surface temperature fronts on the marine atmospheric boundary layer

Skyllingstad

Vickers

Mahrt

et al. 2006

Boundary-Layer Meteorol

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A numerical modelling study is presented focusing on the effects of mesoscale sea-surface temperature (SST) variability on surface fluxes and the marine atmospheric boundary-layer structure. A basic scenario is examined having two regions of SST anomaly with alternating warm/cold or cold/warm water regions. Conditions upstream from the anomaly region have SST values equal to the ambient atmosphere temperature, creating an upstream neutrally stratified boundary layer. Downstream from the anomaly region the SST is also set to the ambient atmosphere value. When the warm anomaly is upstream from the cold anomaly, the downstream boundary layer exhibits a more complex structure because of convective forcing and mixed layer deepening upstream from the cold anomaly. An internal boundary layer forms over the cold anomaly in this case, generating two distinct layers over the downstream region. When the cold anomaly is upstream from the warm anomaly, mixing over the warm anomaly quickly destroys the shallow cold layer, yielding a more uniform downstream boundary-layer vertical structure compared with the warm-tocold case. Analysis of the momentum budget indicates that turbulent momentum flux divergence dominates the velocity field tendency, with pressure forcing accounting for only about 20% of the changes in momentum. Parameterization of surface fluxes and boundary-layer structure at these scales would be very difficult because of their dependence on subgrid-scale SST spatial order. Simulations of similar flow over smaller scale fronts (<5 km) suggest that small-scale SST variability might be parameterized in mesoscale models by relating the effective heat flux to the strength of the SST variance.

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Section: Introductionsupporting

confidence: 83%

Effects of mesoscale sea-surface temperature fronts on the marine atmospheric boundary layer

Skyllingstad

Vickers

Mahrt

et al. 2006

Boundary-Layer Meteorol

Self Cite

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“…As an example, in Fig. 9 a time series of friction velocity values obtained by the FB off Duck, North Carolina, is presented, along with friction velocity measurements obtained from the National Aeronautics and Space Administration (NASA) LongEZ aircraft flying over the buoy at an altitude of approximately 15 m (Mahrt et al 2001). The LongEZ data have been adjusted to surface values.…”

Section: Experiments Resultsmentioning

confidence: 99%

“…These unusual averaging intervals were determined by the physical constraints of the low-powered data acquisition computers used in the buoy. Mahrt et al (1996) indicate that using a local averaging interval of about 10 min for flux determination is long enough to capture all the important eddy scales that contribute to the flux value and short enough to reduce nonstationary effects. Although the data analyzed in this study were obtained near the coast, there was very little evidence of diurnal land-sea wind variations occurring.…”

Section: Data Analysis Proceduresmentioning

confidence: 99%

“…The FB has been deployed in numerous experiments from 1993 to the present, including off the coasts of Norway, Netherlands, North Carolina, Virginia, California, and Hawaii. This dataset has been used to verify remotely measured fluxes (Mahrt et al 2001), develop and evaluate nearsurface optical and electromagnetic propagation models (Frederickson et al 2000), and to investigate the effects of waves on air-sea fluxes.…”

Section: Introductionmentioning

confidence: 99%

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Observational Buoy Studies of Coastal Air–Sea Fluxes

Frederickson

Davidson

2003

J. Climate

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Recent advancements in measurement and analysis techniques have allowed air-sea fluxes to be measured directly from moving platforms at sea relatively easily. These advances should lead to improved surface flux parameterizations, and thus to improved coupled atmosphere-ocean modeling. The Naval Postgraduate School has developed a ''flux buoy'' (FB) that directly measures air-sea fluxes, mean meteorological parameters, and one-dimensional and directional wave spectra. In this study, the FB instrumentation and data analysis techniques are described, and the data collected during two U.S. east coast buoy deployments are used to examine the impact of atmospheric and surface wave properties on air-sea momentum transfer in coastal ocean regions. Data obtained off Duck, North Carolina, clearly show that, for a given wind speed, neutral drag coefficients in offshore winds are higher than those in onshore winds. Offshore wind drag coefficients observed over the wind speed range from 5 to 21 m s Ϫ1were modeled equally well by a linear regression on wind speed, and a Charnock model with a constant of 0.016. Measurements from an FB deployment off Wallops Island, Virginia, show that neutral drag coefficients in onshore winds increase as the wind-wave direction differences increase, especially beyond Ϯ60Њ.

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“…This study analyzes eddy correlation data collected from the LongEZ research aircraft over Atlantic coastal water off the Outer Banks near Duck, North Carolina during the SHOaling Waves EXperiment (SHOWEX) in March 1999 and NovemberDecember 1999 Mahrt et al, 2001) using low-level aircraft data from 37 flights on 35 days at an average height of 15 m above the sea surface. The LongEZ is able to fly at this very low level for several hours at a time.…”

Section: The Datamentioning

confidence: 99%

Surface Fluxes in Under Weak Wind Conditions

Mahrt¹

2001

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Surface stress in offshore flow and quasi‐frictional decoupling

Cited by 23 publications

References 32 publications

Effects of mesoscale sea-surface temperature fronts on the marine atmospheric boundary layer

Effects of mesoscale sea-surface temperature fronts on the marine atmospheric boundary layer

Observational Buoy Studies of Coastal Air–Sea Fluxes

Surface Fluxes in Under Weak Wind Conditions

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