Horizontal Velocity Spectra in an Unstable Surface Layer

J. C. Kaimal NOAA/ERL/Wave Propagation Laboratory, Boulder, Colo. 80302

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Abstract

Data from a boundary-layer experiment conducted over a flat, uniform site in Minnesota provide a clue to the behavior of the low-frequency peak in surface-layer horizontal velocity spectra. This portion of the spectra shows systematic behavior only when plotted in dimensionless coordinates appropriate to the mixed layer, whereas the inertial subrange frequencies follow Monin-Obukhov similarity. Based on this observation, interpolation formulas for both the longitudinal and the lateral velocity components, are derived. The expressions involve the boundary-layer depth in addition to the usual surface-layer parameters.

Abstract

Data from a boundary-layer experiment conducted over a flat, uniform site in Minnesota provide a clue to the behavior of the low-frequency peak in surface-layer horizontal velocity spectra. This portion of the spectra shows systematic behavior only when plotted in dimensionless coordinates appropriate to the mixed layer, whereas the inertial subrange frequencies follow Monin-Obukhov similarity. Based on this observation, interpolation formulas for both the longitudinal and the lateral velocity components, are derived. The expressions involve the boundary-layer depth in addition to the usual surface-layer parameters.

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