C波段多普勒雷达双PRF模式速度混淆区识别和处理方法研究

An algorithm for chaos radial velocity identifying and processing in C band Doppler radars running in the dual PRF mode

中文关键词:  C波段多普勒雷达，双PRF模式，速度混淆区

英文关键词:C-band Doppler radar, Dual PRF mode, Chaos radial velocity

中文摘要:

      中国C波段新一代天气雷达在双PRF工作模式下经常在正（负）速度区出现负（正）速度杂点的情况，严重影响了雷达资料的使用。为了提升雷达径向速度资料的质量，提出了一种对C波段新一代天气雷达在双PRF工作模式下径向速度正负速度混淆区（速度混淆区，下同）的识别和处理方法，并以CINRAD/CC雷达资料为例，分析了识别和处理方法的效果。利用哈尔滨和牡丹江雷达2010年夏季部分时段观测资料进行验证。结果表明，速度混淆区内径向速度值的跳动幅度约为雷达双PRF模式最大不模糊速度值。利用径向速度资料中各点与周围8点径向速度平均差值的分布规律和区域内正、负速度平均值的差值规律，能够正确识别速度混淆区，速度模糊区边界能够得到保留；以速度混淆区各点为中心，通过统计各点邻域内非速度混淆点的正、负速度点个数占非速度混淆点总数的比例，再将最大比例对应的径向速度算术平均值作为该点的径向速度替代值，能够消除并修正原始资料中的速度混淆区；对比原始资料，处理后资料中的速度混淆区被消除，资料质量得到提高。

英文摘要:

      Doppler velocity information can be used for removal of ground clutter, extraction of wind profiles, detection of shear zones, and construction for dual Doppler wind fields. Operational application of Doppler velocity data from weather radars is hampered by the infamous limitation of the range velocity ambiguity. The dual pulse repetition frequency (DPRF) is a commonly used technique, especially in C band new generation weather radars that extend the unambiguous Doppler velocity. However, the region of chaos radial velocity that contained opposite sign velocity values with large differences often occurs in velocity data which obtained from C band new generation weather radars running in the dual PRF mode. It affected radar data quality severely. The characteristics of the chaos radial velocity are analyzed in this paper, and an algorithm for identifying and correcting the chaos radial velocity has been developed and examined based on the volume scanning radar data from Haerbin and Mudanjiang radars in the summer of 2010. The main conclusions are gotten as follows: (1) The signal to noise ratio has definite effects on local velocity change. It is found that where the signal to noise ratio is smaller, the local velocity change is bigger and the probability of chaos radial velocity occurred in velocity data is greater, and vise versa. (2) In the region of chaos radial velocity, the right velocity value is related to the unambiguous Doppler velocity value and the error velocity value. Subtracting the unambiguous Doppler velocity value from the error velocity value when the error velocity value is greater than zero, or adding the unambiguous Doppler velocity value to the error velocity value when the error velocity value is smaller than zero, then we could get the right velocity value. (3) The algorithm uses characteristics of velocity difference that in small region identify the region with big local velocity change, and turns out two characteristic parameters, to distinguish the chaos radial velocity with the margin zone of the velocity aliases kept well. That represents the abrupt changes in region, and the absData shows the average velocity differences in small region within the interval of 0 to 2 ×(Nyquist velocity). And, (4) on the basis of image continuity, the average velocity value with maximum ratio between the positive velocity points and the negative velocity points which are not the chaos radial velocity and are all in the region of K neighborhood can be acted as the new velocity value. In comparison with original velocity data, the region of chaos radial velocity has been retrieved obviously, and the quality of velocity data has been improved.