云分辨尺度下一种综合调整水物质含量的闪电资料同化方法

Assimilation of lightning data through comprehensively nudging water contents at the cloud-resolving scale

在直接调整水汽含量(称为F12)和直接调整冰相粒子浓度(称为Q14)两种闪电资料同化方法的基础上,提出了一种综合调整冰相粒子浓度和水汽含量(称为C17)的闪电资料同化方法,选取一次具有完整闪电观测资料(云闪加地闪)的飑线过程,利用WRF在云分辨尺度进行数值模拟,详细比较了3种闪电资料同化方法的模拟结果。与不进行闪电资料同化的控制试验相比,闪电资料同化试验明显改进了模式对流活动的模拟能力,但是不同同化方法有所差异。在同化时段内,F12方法中回波强度较小,形成大范围层云区,回波中心比实测偏向下游;Q14方法回波强度和落区同实测最为接近,但是对层云区的模拟无明显改进;C17方法综合了F12和Q14方法的优势,与F12方法相比,回波强度增大,落区更加接近实测,层云区面积扩大。同化结束后,F12方法冷池有所增强,雨区向东北方向延伸,但是强度较弱,形成大范围的弱降水区,同化正面效果保持最久;Q14方法低层大气偏干,地表冷池偏强,对流系统迅速移动并衰减,降水区域比实测偏南,同化正面效果消失较快;C17方法冷池范围和强度与实际观测最为接近,降水较F12方法增强,模拟出的飑线形态得到调整,模拟出了实测中的另一降水中心,同化正面效果保持时间延长。

Based on the two methods of assimilating lightning data that directly increase water vapor by Ficrro et al. （denoted F12） and ice-phase particles by Qie et al. （denoted Q14）, a combined method that comprehensively increases both water yapor and ice phase particles （denoted C17） was presented. A squall line case with accurate total lightning observations was chosen to compare the effects of the three lightning assimilation methods mentioned above. Compared with the control experiment, the experiments that assimilated lightning data showed improved simulation for convection. However, the simulations differed in experiments with different assimilation methods. During the assimilation period, the convections were weak in the F12 experi ment, while large areas of stratiform clouds formed and the convective core was located downstream of the observation. The in tensity and location of convections simulated in the Q14 experiment agreed well with observations, but the simulation of stati form clouds was not improved. The convections in the C17 simulation strengthened with more accurate positions compared with that simulated in the F12, while a larger area of stratiform clouds formed compared to that in the Q14. After the assimilation, the cold pool strengthened while light precipitation extended northeastward in the F12 experiment, suggesting that the positive impacts of lightning assimilation was sustainable. The relatively dry lower-atmosphere in the Q14 resulted in a stronger cold pool and a fast-moving squall line that weakened quickly, while precipitation shifted southward compared to observations, indi eating that the positive impacts of lightning assimilation faded soon. The C17 performed best in simulating the coverage and magnitude of the cold pool and the morphology of the squall line with long lasting positive impacts of lightning assimilation, and large precipitation was successfully simulated.