Wind retrieval and its verification for the oceaneffect snowstorms using the EVAP method.

A formula to calculate the horizontal radial velocity at different heights via the several elevation angles from a Doppler radar was derived with the falling speed of cloud/rain particle covered but the vertical velocity neglected. Then the two dimensional horizontal wind field on the isohypsic surface was retrieved by the VAP technology. This method is called the Extended VAP (EVAP). Two different snowstorm samples occurred in the Shandong peninsula in December 2005 were retrieved to verify the EVAP method, the radial velocity and reflectivity interpolated and compared with the retrieved wind on the every isohypsic surface. In addition, the retrieved wind fields were compared with the observational data from the automatic meteorological stations and synoptic charts as well. The comparative results show that the retrieved wind fields at different heights accord with the observational data. Mesoscale wind structure of oceaneffect snowstorms is further analyzed in this paper with the result that the shears between the retrieved southwestern and northeastern wind as well as between the retrieved northwestern and northeastern wind are corresponding with the strong reflectivity zones suggesting that the EVAP method is able to correctly retrieve wind of the different weather systems. As a result, the retrieved wind fields of high spatial and temporal resolution remedy the defect that only the wind of larger scale can be analysed conventionally. Calculation of the retrieving wind for one volume scan needs just less than one minute. So the EVAP technology can be applied to the operational nowcasting of oceaneffect snowstorm.