华南一次强飑线过程的三维变分风场反演效果分析

利用三维变分方法对2014年3月30—31日华南一次强飑线过程进行风场反演,经与风廓线雷达探测结果、双多普勒天气雷达反演结果、原始径向速度数据等对比分析,得到如下结论：三维变分方法反演的中低层水平风场与风廓线雷达探测到的结果较为一致,且能很好地表现飑线过境时的风向切变;通过与双多普勒雷达风场反演结果对比发现,两种方法得到的风场空间分布十分相似,均能很好地表现2 km高度上系统内部强带状回波前缘的辐合线以及5 km高度上较弱的辐散;三维变分方法反演的水平风场与径向速度场有较好的一致性,2 km高度强回波带前缘阵风锋处的辐合线位置以及5 km和8 km高度上辐散区的位置均与径向速度场十分吻合;三维变分方法反演的垂直速度能较好地反映该飑线过程中气流的上升和下沉运动,平行于飑线方向的气流变化较小,而系统气流变化主要沿垂直于飑线的方向。三维变分方法反演的飑线系统的三维风场结构合理,反演结果可靠。

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

Three-dimensional variation assimilation retrieval （3DVAR） is used to retrieve the wind field of a squall line event in southern China 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 wind structure in the mid- and low-level retrieved by 3DVAR is well consistent with that from WPR, and it can reproduce the wind shear while the squall line is passing. Contrast analysis of the wind retrieved from 3DVAR and that from dual Doppler weather radars found that the former is very similar to the latter; namely, they all can reproduce the convergence line in leading edge of the strong belt-shaped echoes at 2 km height and the week divergence at 5 km height in the squall line system. The horizontal wind field from 3DVAR is well in accordance with the radial velocity 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 the divergence zone at 5 km and 8 km height tally well with the result from radial velocity. The vertical velocity field retrieved from 3DVAR well reveals the ascending motion and the descending motion of air current in this squall line event. The airflow paralleling to the squall line varies little, but that being perpendicular to the squall line varies significantly. Overall, the wind three-dimensional structure of the squall line retrieved by 3DVAR is reasonable, and their results are very dependable.