单Doppler雷达IVAP风场反演试验

单Doppler雷达风场反演技术对于扩大Doppler雷达在中尺度气象监测和预报中的应用范围具有重要的作用。通过采用"给定方位角内风场均匀假定"提出积分速度—方位处理技术IVAP(Integrating Velocity-azimuth Processing),克服了VAP技术在单多普勒雷达风场反演中对Doppler速度小尺度脉动过分敏感的缺点,及VAD(Velocity-azimuth Display,速度-方位显示)技术只能反演平均风矢量问题。利用2001-08-05上海特大暴雨时虹桥机场Doppler雷达速度资料进行中尺度风场反演试验。对均匀风方位角区间分别取9?,18?,45?和90?的反演结果的比较表明,采用较小的方位角区间可以反演出与这次暴雨有关的气旋式环流和中尺度辐合线。利用地面站实测风记录及风廓线数据对IVAP反演风的质量进行了评估。结果表明,反演风的风向和地面实测风的风向有很好的相关性,反演方位角区间越大,相关性越好。与20个时次同高度上风廓线仪探测的风速数据的对比表明,IVAP技术反演出的风速和它们也有很好的相关性,两者u、v分量均方误差在2m/s左右。由于IVAP技术风场反演无需事先对Doppler雷达原始的速度资料进行人为的滤波或平滑处理,所以具有较强的客观性,便于在气象雷达预报业务中应用。

Experiments on the IVAP Single-Doppler Radar Wind Retrieval Method

The single-Doppler radar wind retrieval method is useful to enhance the applications of the Doppler radar in the observing and forecasting of mesoscale weather system. This paper shows that the VAD and VAP methods can all be derived from the same relationship based on the azimuthal uniform wind assumption. By using this assumption, an IVAP (Integrating VAP) method is developed, which can overcome the sensitivity of VAP method to the short wave and too smooth property of VAD method in Doppler velocity. By using the IVAP technique, the wind fields associated with a heavy rainfall case in Shanghai (Aug. 5th 2001) are retrieved using a Doppler radar located at the Hongqiao Airport. Retrieved winds using azimuthal sector length of 9,18,45, and 90 indicate that using shorter sector length can exhibit the cyclonic stream and mesoscale convergence line related to the heavy rainfall. The quality of the retrieved winds is validated by using surface observations and wind-profiler data. Comparison of the radar retrieved winds with surface observed winds indicates that retrieved winds have good correlation with surface observations. The larger the sector length the higher is the correlation coefficient. Twenty wind-profiler data at the same height and time also have good correlation with Doppler radar retrieved winds. The square mean errors of u or v are about 2 ms-1. All of the results indicate that the IVAP method is more objective to be used in applications of Doppler radar.