多普勒雷达速度场缺测区域填补技术的数值模拟

Numerical Simulation of Filling Doppler Velocity Field in Non-Echo Areas

针对多普勒天气雷达探测风场时,常因大面积无回波区的存在,对提取平均散度和平均形变信息的精度有较大影响。利用Sirmans建议的技术来模拟降水回波信号,得到含有0、1、2阶谐波的平面线性速度场并进行加噪处理,得到近乎真实的多普勒速度场。对模拟的平面线性速度场人为设定无回波区,利用VAD技术和迭代法对平面线性速度场做连续性缺口和非连续性缺口的迭代法填补。数值模拟结果表明:对于模拟的无噪声平面线性速度场,迭代法可以基本无误差填补连续性累积缺口在10°到180°的速度场无回波区;对连续性累积缺口,在σ_v=2m·s^(-1),SNR≥5 dB和SNR=20 dB,σ_v≤4 m·s^(-1)的情况下,连续性累积缺口在120°以内,迭代法能较高精度地填补速度场无回波区,填补后0、1、2阶谐波误差绝对值基本能控制在15%以内,80 km距离圈上缺口处迭代前后速度相对误差均在30%以内;对非连续性累积缺口为0°～180°的平面线性速度场,在附加不同噪声条件下,迭代法均可较好地填补累积缺口在180°以内的平面速度场,且80 km距离圈上缺口处迭代前后速度值误差均能控制在15%以内。说明利用迭代法填补多普勒速度场无回波区,填补效果较好,精度较高,这对改善从多普勒速度场中提取平均散度和平均形变信息的精度有极大的帮助作用。

When wind field is detected with Dopper weather radar,there are some different size non-echo areas in large-scale radar echoes,which lead to great errors when average divergence and average deformation information are extracted.With the technique suggested by Sirmans to simulate the precipitation-echo signal,we obtain a plane linear velocity field which includes 0,1,2 step overtones and carry on adds-chirp processing,and then a near-real Doppler velocity field is generated.Supposing that the special non-echo area exists in the plane linear velocity field and by the use of VAD technology and the repetitive processing,the continuous gap and the non-continuous gap in the plane linear velocity field would be filled with repetitive processing.The simulation results indicate that for the simulation of non-noise plane linear velocity field,the non-echo area of continuity accumulation gap from 10°to 180°can be filled inerrably with the repetitive processing in the velocity field.For continuous accumulation gap, under the conditions ofσ_v=2 m·s^（-1）,SNR≥5 dB and SNR=20 dB,σ_v≤4 m·s^（-1）,and the continuous accumulation gap less than 120°,the non-echo area with the repetitive processing in the velocity field can be filled inerrably. After filling,the absolute errors of 0,1,2 step overtones may be controlled to be less than 15%,and the absolute errors of speed controlled less than 30%which is 80 km away from the circle around the gap place iteration. For the plane linear velocity field of non-continuous accumulation gap from 0°to 180°,under the condition of addi- tional different noise,not only the accumulation gap less than 180°in the plane velocity field can be filled,but also the speed errors can be controlled to be less than 15%which is 80 km away from the circle around the gap place iteration. This shows that the effect and precision are very good when nonecho areas in Doppler wind field are filled with the repetitive processing,and will have a great help for improving the precision of average divergence and average deformation information extracted from the Doppler wind field.