A comparative study of two new approaches to estimate the vertical wind profile from aliased radial velocities

Because of the limited value of the sampling frequency (Pulse Repetition Fr equency), meteorological Doppler radars provide the radial velocity of hydr ometeors within a given interval bounded by the so-called Nyquist velocity. Dealiasing radial velocities is a time-consuming process, which can be a s erious drawback in an operational context. We propose and compare two appro aches designed to estimate the vertical wind profile above the radar direct ly from the raw (i.e. aliased) radar data set. Both methods rely on a first order VAD expansion of the horizontal wind components. The first one follo ws exactly the VAD analysis except that the radial velocity is replaced by its azimutal derivative. Thus, it is not necessary to know in which Nyquist interval each measurement is. The second is based on Bayesian updatings an d consists in initially selecting a collection of equiprobable wind profile s and in modifying their probabilities each time a measurement comes up. Bo th methods are detailed and compared in terms of computing time, robustness and accuracy. (C) 2000 Elsevier Science Ltd. All rights reserved.