A New Radar Scan Mode to Increase Clear-Air Velocity Data Coverage and Usability for Wind Analysis

Abstract

AbstractBy using long pulses with extended dwell time, radar sensitivity is enhanced such that more clear-air returns are usable. This enhanced capability can increase clear-air data coverage and provide additional information for radar wind analysis and data assimilation. To explore this potential capability and related benefits, a new scan mode with long pulses and low antenna rotation rate is derived from the existing clear-air scan mode and applied to the named KOUN S-band test bed radar at NSSL. Velocities collected using this newly modified scan mode are significantly enhanced in data coverage compared to those collected with the unmodified scan mode from the nearby test bed radar (named KCRI). However, transmitter duty cycle limits the pulse repetition frequency (PRF) to 455 Hz for the long pulses, which reduces the Nyquist velocity to 12.53 m s−1 for the new scan mode. Such a small Nyquist interval leads to significantly worse problems with aliased velocities. A recently developed dealiasing algorithm is modified by using external reference velocities from KCRI to overcome increased difficulties in dealiasing, making the velocities from KOUN useful over increased range and area. This implies that similar increases in velocity data coverage can be achieved without using external reference velocities if the newly modified scan is paired with an unmodified scan into dual-PRF scans. This dual-PRF approach is proposed for future development.