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Surface Roughness and Internal Boundary Layer Near a Coastline

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  • 1 Atmospheric Science Group, The University of Texas at Austin
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Abstract

Wind profile observations obtained at two sites near the upper Texas coast during onshore winds in June 1968 are used to determine local toughness parameters. Values of 3–4 cm are obtained at a 32 m tower site 90 m inland and 0.81–1.5 cm at 4.8 km inland; both are in close agreement with results of others for similar terrain. The portion of the wind profile obtained at heights between 6.7 and 27 m near the beach is extrapolated downward to obtain a roughness between 0,0001 and 0.0003 cm for the Gulf of Mexico.

An internal boundary layer was detected from the data obtained 90 m inland. The mean height was observed to he 6.7 m— a value associated with a mean slope of about 1:13 for an internal boundary originating at the upwind shoreline roughness discontinuity. Daytime values for the internal boundary height are somewhat higher than the mean, averaging 7.2 m, while the nighttime mean is 5.9 m. The data also suggest a wind speed dependence on the height of the internal boundary layer.

Abstract

Wind profile observations obtained at two sites near the upper Texas coast during onshore winds in June 1968 are used to determine local toughness parameters. Values of 3–4 cm are obtained at a 32 m tower site 90 m inland and 0.81–1.5 cm at 4.8 km inland; both are in close agreement with results of others for similar terrain. The portion of the wind profile obtained at heights between 6.7 and 27 m near the beach is extrapolated downward to obtain a roughness between 0,0001 and 0.0003 cm for the Gulf of Mexico.

An internal boundary layer was detected from the data obtained 90 m inland. The mean height was observed to he 6.7 m— a value associated with a mean slope of about 1:13 for an internal boundary originating at the upwind shoreline roughness discontinuity. Daytime values for the internal boundary height are somewhat higher than the mean, averaging 7.2 m, while the nighttime mean is 5.9 m. The data also suggest a wind speed dependence on the height of the internal boundary layer.

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