Horizontal velocity spectra in an unstable surface layer.

Abstract

Data from a boundary-layer experiment conducted over a flat, uniform site in Minnesota provide a clue to the behaviour of the low-frequency peak in surface-layer horizontal velocity spectra. This portion of the spectra shows systematic behaviour 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 formulae 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. (A)