Fig. 1

Schematic representation of the method used for estimating pseudo-vertical profiles of Doppler variances \(\sigma^{2}\) from radar data. (Left) Example of horizontal excursion of a UAV with respect to MU radar antenna array location (black dot). (Right) The corresponding UAV altitude versus time (black line). The blue and red areas indicate the time-height domain used for calculating the average of Doppler variances \(\sigma^{2}\) during the ascent and descent of the UAV, respectively. Time averaging for a given altitude was arbitrarily performed over 4 min centered at the time when the UAV reached this altitude