Vertical Velocity Turbulence Observed with FMCW Radar

Very fine space and time resolution observations of clear air reflectivity and vertical velocity were obtained in a day-time convective boundary layer by a frequency-modulated continuous-wave radar. Historically, most atmospheric FMCW radar investigations have focused on the extremely fine range resolution of which such radars are capable. When used in this mode, Doppler velocity information is usually lost due to the long integration time of the frequency sweep. That is, the effective pulse repetition frequency of the radar is so low that the Nyquist velocity interval is too narrow for useful measurements of atmospheric velocities. However, when configured for rapid profiling at the expense of either height coverage or spatial resolution, FMCW radars are capable of obtaining Doppler velocity timeseries from moderately sized resolution volumes at rates of several Hz. These are sufficient to resolve turbulent velocity variations in the inertial subrange down to timescales of approximately one second or less.