初始场与云微物理参数方案在飑线数值模拟中的对比研究

The Comparative Study of Initial Field and Cloud Microphysical Parameter Scheme in the Numerical Simulation of Squall Line

采用CM1模式以200 m的高精度水平网格距对一次东北冷涡下的飑线过程进行模拟,采用1 km的水平网格距进行对比试验探究网格距的影响,并通过探空资料的替换与修改研究不稳定能量和垂直风切变对飑线发展的影响。研究表明,水平网格距增大主要使系统演变减缓,强度也有一定的减弱;初始场的不稳定能量减小会使飑线减弱明显,直至无法生成;垂直风切变对飑线的形成影响较小,主要改变了飑线的结构,没有垂直风切变时形成的飑线更为松散。最后的敏感性试验研究了7种云微物理参数方案对飑线内水粒子分布的影响,发现不同的云微物理参数方案会使水粒子的含量和分布出现变化,进一步影响固、液态的降水,飑线模拟采用的NA方案高层冰和雪含量最高,但由于雨和降落到地表的雹、霰含量低,使得累计降水量最小。

The paper adopts the CM1 model to simulate the process of a squall line under the background of Northeast Cold Vortex with a high precision horizontal grid distance of 200 m.Comparative experiment was carried out with a horizontal grid spacing of 1 km to explore the influence of grid spacing on squall line,and the influence of unstable energy and vertical wind shear on the squall line is studied through the replacement and modification of the sounding data.It is found that the increase of horizontal grid spacing mainly slows down the evolution of the system,and the strength of system is also weakened.The decrease of unstable energy of the initial field will cause the squall line to weaken obviously and the squall line can not be generated when the unstable energy is reduced to 0.The vertical wind shear has little effect on the formation of the squall line,which mainly changes the structure of the squall line,and when there is no vertical wind shear in the initial field,the squall line is more loosely in structure.Finally,the sensitivity test studied the influence of seven cloud microphysical parameter schemes on the distribution of water particles in squall line.It is found that different schemes of cloud microphysical parameters will change the content and distribution of water particles and further affect the precipitation of solid and liquid,and lead to different precipitation intensity.The solid water particles of the NASAGoddard version of LFO(NA)scheme used in the simulation of squall line are mainly snow,and has the highest ice and snow content in the upper layer,however,due to snow and ice did not fall to the surface,and the content of rain,hail and graupel are less than other schemes,the accumulated precipitation is minimal.