水平风场线性假设EVAD技术的改进及其风场代表性分析

Improvement of Traditional EVAD Technology and Analysis on Representativeness of Mean Wind Field

水平风场线性假设的传统EVAD技术在非线性程度较大的高度层会计算出代表性差的平均风场信息。改善方法就是在EVAD技术计算雷达站上空平均风场信息时剔除掉非线性程度较大的等距离圈,使进入计算的等距离圈较好满足线性假设。研究结果表明,二阶傅里叶级数拟合等距离圈径向速度均方根误差(RMS)大小能表征水平风场非线性程度,RMS越大,非线性程度也就越大,通过设定合理RMS阈值,可以剔除掉非线性程度大的等距离圈从而使传统EVAD技术得到改善。个例中RMS阈值设置为3m/s,可以在一定程度上避免计算出代表性差的平均风场信息,但其合理性需要研究更多个例来验证。高度层内所有等距离圈二阶级数RMS加权平均值,可以表征改善后的EVAD技术计算的平均风场对真实风场的代表性。

The traditional EVAD technology with linear hypothesis results in relatively poor-representativeness mean wind field information in the calculating for upper levels with high nonlinearity.The magnitude of root-mean-square errors of the radial velocities at equidistance rings from the 2-order Fourier series fitting can indicate the level of nonlinearity.The larger the RMS,the larger the nonlinearity is.Setting the proper threshold of RMS can eliminate the relatively large nonlinear rings,which makes the rings in calculation meet the linear assumption.When the nonlinearity of winds is large,the 3 m/s threshold can avoid the bad mean wind instead of ＂ND＂ value.The mean RMS of all rings can reflect the representativeness of the mean wind field for the real wind field.The rationality of the threshold 3 m/s needs to be verified by more cases.