Performance evaluation of 3-dimensional variation assimilation retrieval of wind field of a squall line event insouthern China

Three-dimensional variation assimilation retrieval (3DVAR) is used to retrieve the wind field of a squall line event in southernChina from March July 30 to 31 in 2014. A comparative analysis of the wind field from 3DVAR with the ones from wind profile radar (WPR)observed, dual Doppler weather radars retrieved and Doppler radar radial velocity is performed. Results are as follows. The horizontal windstructure in the mid- and low-level retrieved by 3DVAR is well consistent with that from WPR, and it can reproduce the wind shear while thesquall line is passing. Contrast analysis of the wind retrieved from 3DVAR and that from dual Doppler weather radars found that the former isvery similar to the latter; namely, they all can reproduce the convergence line in leading edge of the strong belt-shaped echoes at 2 km heightand the week divergence at 5 km height in the squall line system. The horizontal wind field from 3DVAR is well in accordance with the radialvelocity field. For example, both the convergence line at the gust front place in leading edge of the strong echoes belt at 2 km height and thedivergence zone at 5 km and 8 km height tally well with the result from radial velocity. The vertical velocity field retrieved from 3DVAR wellreveals the ascending motion and the descending motion of air current in this squall line event. The airflow paralleling to the squall line varieslittle, but that being perpendicular to the squall line varies significantly. Overall, the wind three-dimensional structure of the squall line retrievedby 3DVAR is reasonable, and their results are very dependable.