The Sensitivity of Single Polarization Weather Radar Beam Blockage Correction to Variability in the Vertical Refractivity Gradient

Abstract

Radars operating in complex orographic areas usually suffer from partial or total beam blockage by surrounding targets at their lowest elevation scans. The need for radar quantitative precipitation estimates in such environments led to the development of beam blockage corrections. This paper aims at evaluating the performance of beam blockage corrections under different electromagnetic propagation conditions with particular interest in anaprop situations. Three years of radiosonde data collected at Barcelona, Spain, a typical Mediterranean coastal site, are used to characterize the behavior of the vertical refractivity gradient near a weather radar. Three different targets surrounding the radar have been chosen and used to evaluate the different beam shielding simulated under different propagation conditions. A simple interception function between the radar beam and the topography is proposed and used for the different targets and propagation conditions considered. Results show that beam blockage correction is generally robust, with departures of 1 dB from the standard propagation conditions correction less than 10% of the time. However, as the presence of extreme anaprop cases would lead to higher differences, the monitoring of the propagation conditions is suggested as a criteria to be considered, among others such as the analysis of the echo structure, as a quality control of the radar quantitative precipitation estimate.