The Coherence Time of Mid-Tropospheric Wind Features as a Function of Vertical Wavelength from 300 to 2 Km

The coherence between vertical wind profiles separated by a time lag, L, is measured as a function of vertical wavenumber, k, from Doppler radar wind profiler data. Each profile covers altitudes from 6811 to 16261 meters and is Fourier transformed over a wavenumber range from 0 to 3.33 E-3/m. Time lags between profiles of 0.083, 0.25, 0.5, 1.0 and 2.0 hours are used. A correction for instrument noise is derived and applied to the results. An empirical formula for the coherence as a function of L and k is presented and evaluated. The "coherence time", tau, is defined as the value of L beyond which the coherence decays below a chosen value, epsilon, at a given scale lambda where lambda = 1/k. A relation between tau and lambda is derived. The resolution of the KSC 50 MHz profiler is reassessed.