Study On VVP Wind Field Rertieval Method Of Single Doppler Weather Radar

Since only radial velocity can be observed in wind field detection by the Doppler weather radar, the issue of how to restore the real three-dimension wind field is urgent need to resolve in both meteorological operations and scientific research. In this paper, the VVP (Volume Velocity Processing) retrieval method and the errors in retrieval are analyzed, the equations of retrieving vertical velocity is improved and a new approach performed which based on wind field retrieval technique to identify wind shear is proposed. The main conclusions are as follows:(1) By estimating the upper limit of retrieval error and analyzing the effects of neglected parameters on retrieval accuracy, it can be found that simplified wind model can decrease the difficulty in solving and stabilizing the retrieval results, even though model errors would be induced by neglected partial parameters. Because the coefficient matrix (CM) is a function of the position of the analysis volume, the retrieval errors and the condition number varies with the analysis volume’s position accordingly. Thus, the parameters with small magnitude or small position coefficient can be abandoned to simplify the wind field model.(2) Observation errors and calculation errors are inevitable in retrieval. According to the spread of errors in the solving process, a demonstration by using mathematical deduction is provided to explain that the large analysis volume could improve retrieval accuracy. By analyzing the variation of coefficient matrix’s condition number, it can be demonstrated strong linear correlation among CM vectors would cause singular matrix when fitted parameters are selected. The reason of coefficient matrix ill-conditioned is caused by a combination effort of observation and calculation errors acting on a singular matrix.(3) The modified Volume Velocity Processing method (MVVP) on which vertical wind velocity based is analyzed and the solving equations are improved. It is demonstrated that the accuracy of fitted parameters could be affected when combining or abandoning linear correlation items in coefficient matrix, but partial fitted parameters could remain accuracy, like the vertical parameter in particular wind models. The performance of the MVVP method shows that the vertical movement of particles can be retrieved exactly, which is helpful to reveal the three dimension structure details of severe weather, to locate and forecast the precipitation.(4) After analyzing the traditional techniques which relies on the difference of radial velocity to identify wind shear, a fixed difference among radial velocities that may cause fault identification in uniform wind field was found. Near the zeros contour of Doppler velocity, the fixed difference reaches maximum. Because of the non-uniform wind in shear areas, the difference of retrieval results between nearby analysis volumes would be significant when using uniform model for retrieval, and the difference can be used as a measurement to present the level of wind shear. Based on wind field retrieval technique, an approach performed with radial velocity of Doppler weather radar to identify wind shear is proposed. The results show that the analysis of strong wind shear’s development is helpful to forecast severe convections.