Characteristics of Turbulence Observed at the NASA 150-m Meteorological Tower

Abstract

Recent observations of turbulence obtained at the NASA 150-m meteorological tower located at Kennedy Space Center, Fla., are presented. The wind data were obtained at the 18-, 30-, 60-, 90-, 120- and 150-m levels, while temperature data were obtained at the 3-, 18-, 60-, 120- and 150-m levels. Most of the tests were made during the daylight hours, and the duration time of each test ranged between 30?60 min. A survey of the surface roughness length associated with the tower site is presented. Estimates of the roughness length were calculated with wind profile laws consistent with the Monin-Obukhov similarity hypothesis. In the case of those wind directions ? in the ranges 0° ? ? < 150°, 180° ? ? < 240°, and 300° ? ? < 360°, the roughness length is 0.23 m, while for those wind directions in the ranges 150° ? ? < 180° and 240° ? ? < 300°, the roughness length has the values 0.51 m and 0.65 m, respectively. Longitudinal turbulence spectra calculated from recent observations are also presented. It is shown that the nondimensional frequency nz/u, associated with the peak of the logarithmic spectrum is proportional to z?, where u is the wind speed at height s and n the frequency. Based upon an analysis of the logarithmic spectrum in the inertial subrange, it is implied that the local mechanical production of turbulent energy is balanced by the local viscous dissipation at the 18-m level.