RASS Developments on the VHF Radar at CNRM/Toulouse Height Coverage Optimization

Abstract

A method is presented to optimize the height coverage of virtual temperature profiles using the Radio Acoustic Sounding System (RASS) on a 45-MHz monostatic wind profiler. It has already been shown that the main limitation in the maximum height coverage for VHF radar is the effect of wind that shifts the acoustic wave fronts away from the sensing volume, preventing an efficient backscattering to the radar antenna. Excluding practical possibilities to steer the antenna beams toward the shifted acoustic wave fronts, as used, for example, on the middle- and upper-atmosphere (MU) radar, an alternative method consisting of deploying several acoustic sources around the instrument is considered. For this purpose, a simulation model is used to estimate the height coverage for various numbers and locations of sources according to the wind and temperature profile. The results show that a well-designed distribution around the wind profiler can significantly improve the range coverage of the RASS. This method has been tested not only for given meteorological situations but also for long-term climatological data. Practically, sufficient space of about 300 m is required around the radar antenna, particularly in the direction of the predominant wind.