Abstract: The quasi-geostrophic process was diagnosed for a case of severe cold air breakout under the blocking situation during 16-18 March of 1998. The attention was focused on the relationship between the surface anticyclone and 500hPa blocking high. The results indicate that the cold outbreak is associated with the adjustment of blocking situation in the Ural Area, i.e. the collapsing and rebuilding of the Ural Mountain blocking high. The temperature advections in the lower troposphere shown that the polar cold air invading from the northwest caused the Ural blocking high collapsed, and a new ridge developed rapidly was due to the warm advection on the southwestern side which led to the Ural blocking high rebuilt. In addition, the distribution of the vertical motion on 700hPa shown that the surface high splitting was related to the considerable upward motion located on the southeastern part of surface high.

Key words: severe cold air, blocking high, diagnose

摘要： 对1998年3月中旬一次高空阻塞形势下强冷空气过程进行了诊断分析，着重讨论强冷空气爆发前后地面反气旋活动与高空阻塞形势调整的关系。研究结果表明，强冷空气的爆发与乌拉尔地区阻塞形势的调整(阻塞高压的崩溃和重建)紧密相关。对流层下部的温度平流分析表明，阻塞形势的调整是由于阻塞高压上游西北方有冷空气侵入导致了阻塞高压的崩溃，而上游来自西南方向的强暖流则导致高压脊迅速发展，使阻塞高压重新建立。另外，700hPa垂直速度分布表明，冷空气的酝酿和爆发与次级环流由反环流转变为正环流相联系。

关键词: 冷空气, 阻塞形势, 诊断