SPECTRAL SCALING OF STATIC PRESSURE-FLUCTUATIONS IN THE ATMOSPHERIC SURFACE-LAYER - THE INTERACTION BETWEEN LARGE AND SMALL SCALES

Static pressure fluctuations measured in the atmospheric surface layer over a grass covered forest clearing are studied in the context of To wnsend's 1961 hypothesis regarding the effect of the outer region on t he inner region. It is shown that large-scale pressure features are ac tively straining the inertial-scale pressure fluctuations, thus invali dating the direct extension of Kolmogorov's 1941 hypothesis to the spe ctral scaling of pressure within the inertial subrange. A parameter de scribing the large scale pressure fluctuations is added to the set of variables responsible for inertial-range pressure differences and dime nsional analysis is employed to derive an improved scaling law for pre ssure spectra which more closely matches these and previous experiment al results. An examination of the Poisson equation for pressure is con ducted and found to support the dimensional and experimental results. (C) 1998 American Institute of Physics.