“96.1”高原暴雪过程湿对称不稳定的诊断分析  

The Diagnosis of Symmetric Instability of “96.1” Snowstorm

作　　者：王文[1] 程麟生[1] 

机构地区：[1]兰州大学资源环境学院大气科学系,甘肃兰州730000

出　　处：《兰州大学学报（自然科学版）》2001年第1期109-120,共12页Journal of Lanzhou University(Natural Sciences)

基　　金：国家自然科学基金! (497752 71 )资助项目

摘　　要：利用对“96.1”青藏高原东北部暴雪过程一次较成功模拟的 MM4中尺度模式输出资料 ,根据条件对称不稳定 (CSI)的线性和非线性理论判据对这次暴雪过程进行了诊断分析 ,结果表明 ,“96.1”暴雪的发生发展过程与条件对称不稳定密切相关 ,不稳定区位置在 M-θe和σ2垂直剖面图上较其它判据更接近于实际情况 .非线性 CSI判据的动力学诊断分析指出 ,“96.1”暴雪是在低空对流不稳定和高空对称不稳定的相互作用下发生发展的 ,说明非线性对流—对称不稳定是其发展机制 .With the criteria of linear and non linear symmetric instability,the mechanism of a heavy snowstorm which occurred in the northeast region over Qinghai Xizang Plateau from 15 to 17 January 1996 (“96.1”) was diagnosed by using two time level output data of a MM4 mesoscale numerical model which well simulated the developing structure and evolution of the “96.1” heavy snowstorm.The results show that the location of positive value of σ 2 is corresponding to that of shear line of the snowstorm; and from the vertical cross section chart of pseudo angular momentum and potential equivalent temperature (M θ e), it can be seen that the region where the slope of surface is more vertical than the M is also consistent to the movement of θ e the snowstorm.The linear conditional symmetric instability is a possible explanation for the shear line.The Lagrangian parcel theory was applied to diagnose the “96.1” snowstorm; and it showed a strong vertical convection at the low level and a slantwise convection at the high level during the snowstorm process.It can be convinced that the convective symmetric instability is a mechanism of the snowstorm development.And the cusp catastrophe is corresponding to the developement and movement of the shear line;limited comparison lends some support to the hypothesis that non linear CSI can be a dominant formative mechanism of the snowstorm,though more sophisticated studies are required.

关 键 词：高原暴雪 非线性对流-对称不稳定 诊断分析 发生机制 发展机制 低空对流不稳定 高空对称不稳定 

分 类 号：P426.634[天文地球—大气科学及气象学]