一种自动多普勒雷达速度退模糊算法研究

Study of an Automated Doppler Radar Velocity Dealiasing Algorithm

提出了一种能解决孤立风暴、高切变和强台风等情况下速度模糊问题的自动多普勒雷达速度退模糊算法。该算法首先通过搜索最弱风区,第一次确定的最多两组初始参考径向和参考速度库,其中使用了相邻仰角初始参考径向应具有方位连续性的约束条件,剔除假零速度线引起的不恰当备用初始径向;然后从初始参考径向和参考速度库开始,对其周围邻近的速度库进行连续性检查,如果当前库的径向速度与参考速度的差值大于给定阈值就对其进行纠正;完成两次全方位径向退模糊处理后,算法进行径向和方位方向的强风切变检查,如果还有强风切变存在,那么通过搜索弱风切变区中有效速度库最多的径向,第二次确定一组退模糊的初始参考径向和参考速度库,再重复前面的退模糊过程,这有利于远离雷达的孤立风暴的速度退模糊。在多次退模糊过程中,判断速度模糊的标准由紧到松,切变阈值由小到大,以确保用于后面退模糊处理的参考速度的可靠性。利用我国S波段多普勒天气雷达观测的龙卷、飑线、孤立强风暴及台风等事件的1 000多个体扫资料对该算法进行了测试和评估,结果表明,速度退模糊准确率>99.5%。对于孤立风暴、高切变及强台风等复杂情况下的速度退模糊来说,新算法要优于我国新一代天气雷达业务退模糊方案。

Based on the horizontal continuity of velocity field, an automated Doppler radar velocity dealiasing algorithm which can solve velocity aliasing problem in isolated severe windstorm events, high shear environment and severe typhoon events are proposed. Most two sets of initial reference radials and gates by finding the weakest wind region is firstly determined in the algorithm, using the adjacent elevation initial reference radials in the azimuth continuity constraint condition and initial reserve radials of elimina- ting inappropriate induced by false zero isodops. Then from these initial reference radials and gates, conti- nuity checks adjacent gates and corrects for the differences between radial velocity values and reference ve- locity the larger than the given threshold. Alter twice round of radial-by-radial dealiasing, the algorithm will perform high gate-to-gate wind shear checking in the radial and azimuth directions, if the high wind shear still exists, it will second determine a set of initial reference radial and gate by finding the weak wind shear radial with the most valid velocity gates, then the preceding dealiasing procedures are repeated one time, which is needed for dealiasing velocities in isolated storm region away from the radar. Multiple pas- ses of dealiasing are performed in the algorithm that use very strict criteria and little shear threshold in ear- lier passes and relaxed criteria and large shear threshold in the later passes to ensure a good reference for dealiasing in the later passes. The dealiasing algorithm is tested and evaluated across more than 1 000 vol- ume scans of S-band Doppler weather radar from China encompassing events of tornadoes, squall lines, isolated strong storms and severe typhoons. The results show that the algorithm is very robust. It can cor- rect for aliased Doppler velocity data properly in more than 99.5% of the cases tested and examined. In ca- ses with isolated windstorm, high shears and severe typhoons, the new algorithm shows the improvement in the current China New Generation Weather Radar operational velocity dealiasing scheme.