Spectral Measurements in a Disturbed Boundary Layer over Snow

Abstract

Abstract I have measured time series of the turbulent fluctuations in longitudinal (u) and vertical (w) velocity and in temperature (t) and humidity (q) with fast-responding sensors in the near-neutrally stable surface layer over a snow-covered field. The series yielded individual spectra, u-w, w-t, w-q, and t-q cospectra and phase and coherence spectra for nondimensional frequencies (fz/U) from roughly 0.001 to 10. This is, thus, one of the most extensive spectral sets over collected over a snow-covered surface. With the exception of the u-w cospectra, all of the spectra and cospectra displayed the expected dependence on frequency in an inertial or inertial-convective subrange. All, however, contained significantly move energy at low frequency than the Kansas neutral-stability spectra and cospectra. This excess low-frequency energy and the erratic behavior of the u-w cospectra imply that the forested bills bordering the site on two sides were producing disturbances in the flow field at scales roughly equ...