Surface wind measurements in three Gulf Coast hurricanes of 2005

Masters, Forrest J.; Tieleman, H. W.; Balderrama, Juan A.

doi:10.1016/j.jweia.2010.04.003

Cited by 46 publications

(36 citation statements)

References 15 publications

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“…The boundary-layer rolls also magnify the ratio of the variation of longitudinal fluctuating velocity to friction velocity in tropical cyclones (Masters et al 2010;Li et al 2012) and other flows with convective turbulence (Smedman et al 2007). …”

Section: Introductionmentioning

confidence: 99%

Turbulence Spectra for Boundary-Layer Winds in Tropical Cyclones: A Conceptual Framework and Field Measurements at Coastlines

Kareem

Hunt

et al. 2014

Boundary-Layer Meteorol

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A conceptual model is proposed for the characteristic sub-ranges in the velocity and temperature spectra in the boundary layer of tropical cyclones (hurricanes or typhoons). The model is based on observations and computation of radial and vertical profiles of the mean flow and turbulence, and on the interpretation of eddy mechanisms determined by shear (namely roll and streak structures near the surface), convection, rotation, blocking and sheltering effects at the ground/sea surface and in internal shear layers. The significant subranges, as the frequency increases, are associated with larger energy containing eddies, shear and blocking, inertial transfer between large and small scales, and intense small-scale eddies generated near the surface caused by waves, coastal roughness change, and the buoyancy force associated with the evaporation of spray droplets. These sub-ranges vary with the locations at which the spectra are measured, i.e. the level z in relation to the height z max of the peak mean velocity and the depth h of the boundary layer, and the radius r in relation to the eyewall radius R ew and the outer-vortex radius R ov . For two tropical cyclones (Nuri and Hagupit), experimental data were analyzed. Spectra were measured where r is near to R ew and R ov using four 1-h long datasets at coastal towers, at 10-and 60-m heights for tropical cyclone Nuri, and at 60-m height for tropical cyclone Hagupit at the south China coast. The field measurements of spectra within the boundary layer show significant sub-ranges of self-similar energy spectra (lying between the length scale 1,000 m and the smallest scales less than 40 m) that are consistent with the above conceptual model of the surface layer. However, with very high wind speeds near the eyewall, the energy of the independently 123 L. Li et al. generated intense surface eddy motions, associated with surface waves and water droplets in the airflow, greatly exceeds the energies of the small scales in the inertial sub-range of the boundary layer, over scales less than about 3-40 m depending on the height z and the radius r . This rise in the small-scale frequency weighted spectra (nS u (n), where n is natural frequency, and S u (n) is the energy spectrum of the longitudinal wind component) is consistent with the hypothesis that these processes are only weakly correlated with the main boundary-layer turbulence.

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Section: Introductionmentioning

confidence: 99%

Turbulence Spectra for Boundary-Layer Winds in Tropical Cyclones: A Conceptual Framework and Field Measurements at Coastlines

Kareem

Hunt

et al. 2014

Boundary-Layer Meteorol

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“…The GF is dependent on the instrument height z, z 0 , the gust duration t, and the averaging duration T. It has been widely studied in winter storms (e.g., Durst 1960;Ashcroft 1994), thunderstorms (e.g., Choi and Hidayat 2002;Orwig and Schroeder 2007), and tropical cyclones (e.g., Krayer and Marshall 1992;Vickery and Skerlj 2005;Masters et al 2010), and is recognized to increase with the height and density of the upwind terrain elements. A small value indicates aerodynamically smooth conditions, such as a bay or a fallow field, and a large value indicates the presence of large obstructions, such as buildings or trees.…”

mentioning

confidence: 99%

Toward Objective, Standardized Intensity Estimates from Surface Wind Speed Observations

Masters¹,

Vickery²,

Bacon³

et al. 2010

Bull. Amer. Meteor. Soc.

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101

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“…While every effort is made to ensure stations are placed in open terrain with a relatively homogeneous upstream exposure, such as that typically found at airports, this is not always possible, and stations are often placed in less than ideal situations. In reporting on surface wind measurements made during three landfalling tropical cyclones along the Gulf Coast in 2005, Masters et al (2010) noted that for station site T5 in Hurricane Rita (2005) positive values of u w were recorded at a height of 10 m for westerly and northerly winds. This means that for these wind directions the momentum flux is directed away from the surface, rather than towards it as would be expected in the atmospheric surface layer.…”

Section: General Site Characteristicsmentioning

confidence: 99%

Aspects of Observed Gust Factors in Landfalling Tropical Cyclones: Gust Components, Terrain, and Upstream Fetch Effects

Miller

Balderrama

Masters

2014

Boundary-Layer Meteorol

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Using wind-speed records from mobile weather stations deployed in tropical cyclones making landfall along the United States coastline over the period 1998-2008, an analysis was made of the gust factors observed in near-neutral conditions by station site and wind direction. The dataset used contained a total of 56 individual station site/wind-direction combinations representative of a wide variety of terrain conditions, ranging from open water to urban exposures. Consideration of the peak gust measured along a given axis, together with the associated components measured simultaneously along the other two axes, showed that peak along-wind gusts are primarily associated with vertical velocities in air moving towards the surface, while peak downwards and upwards vertical gusts are associated with alongwind velocity components that are respectively larger and smaller than the mean along-wind velocity. This behaviour is directly related to the value of the primary component of the surface shear stress in the coordinate system used for the analysis, which involves the product of the along-wind and vertical velocity components and which must be negative in the surface layer. Grouping the mean gust-factor curves for each velocity component into bins based on the turbulence intensity showed that the individual curves in a given bin could not all be considered to be drawn from the same underlying parent distribution, an observation that was confirmed by statistical testing. A quantitative exploration of the effects of upstream terrain variations on the observed gust factors for a selected number of sites suggested that the gust factors and other flow parameters, such as the turbulence intensity, are heavily influenced by the upstream terrain at many of the station sites considered.

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Surface wind measurements in three Gulf Coast hurricanes of 2005

Cited by 46 publications

References 15 publications

Turbulence Spectra for Boundary-Layer Winds in Tropical Cyclones: A Conceptual Framework and Field Measurements at Coastlines

Turbulence Spectra for Boundary-Layer Winds in Tropical Cyclones: A Conceptual Framework and Field Measurements at Coastlines

Toward Objective, Standardized Intensity Estimates from Surface Wind Speed Observations

Aspects of Observed Gust Factors in Landfalling Tropical Cyclones: Gust Components, Terrain, and Upstream Fetch Effects

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