Simultaneous Measurements of Turbulence in the Lower Atmosphere Using Sodar and Aircraft

Abstract

Simultaneous measurements of CT2 and CV2 were made using a calibrated Doppler sodar and a research aircraft equipped with meteorological and turbulence sensors. In each experiment a region of specific interest was identified using the sodar and then the aircraft vectored into it using air-ground radio. Measurements were made in both “layers” (with and without detectable turbulence and “waves”) and in convective plumes. In each case the spectra of turbulent temperature and velocity fluctuations derived from the in situ observations showed a well-developed inertial subrange. Excellent agreement was found between the magnitude of the in situ aircraft CT2 and CV2 values and those derived from the sodar signals interpreted using the Tatarski scattering theory. Examples are shown of how sodar may be used for real-time, quantitative estimates of the dissipation rate of turbulent kinetic energy ε, and the rate of destruction of temperature variance N. On the present Penn State sodar system the operator may select a display of CT2, CV2, ε, N or winds derived from signal Doppler shifts. Either time series at selected heights, vertical time sections on a color, digital video display, or conventional printed or graphical output may be produced.