低纬高原一次强冷空气天气过程诊断分析

Diagnostic analysis of a strong cold synoptic process in low latitude plateau

利用常规气象观测资料、卫星云图、NCEP再分析资料详细分析了2011年1月16—18日低纬高原出现的强冷空气过程.结果表明:此次天气过程主要受深厚的南支槽、高低空急流和冷锋切变影响,南支槽和西南低空急流输送了大量水汽,并在云南中西部聚集,提供了有利的水汽条件;降雪区与TBB≤240 K冷云区基本吻合,TBB低值区的出现和消失,对降雪的增强和减弱有一定的预示作用.雷暴区和冰雹区位于TBB梯度最大处,TBB梯度增强和减弱对雷暴和冰雹天气的出现和减弱有一定的指示作用.降雪站近地层温度较低,整层水汽条件较好,低层有水汽辐合中心,上升运动强烈,且有低层辐合高层辐散的散度场配置.降雹站低层有逆温层,具备较大的不稳定能量、中层有干冷空气侵入,上升运动弱于降雪区,有低层辐合高层辐散的散度场配置.0℃层位于3 km左右的700 h Pa层附近,这个高度更有利于出现大冰雹.降水站水汽条件好,但水汽辐合强度弱于降雪区,上升运动强度与降雹区相当,没有低空辐合高空辐散的散度场.

The conventional meteorological data,satellite cloud images,NCEP reanalysis data are used to analysis the strong cold air process occurring in low latitude plateau during 16-18 January 2011.The results show that the process is mainly affected by deeply south branch trough,upper- level jet stream,low- level jet stream and cold front shear.South branch trough and low-level southwest jet transport a large number of water vapor to Yunnan and gathered in the Midwest of Yunnan. It is a favorable moisture conditions for the synoptic process.Snowfall area fits with cold cloud area which TBB≤240 K.The appearing and disappearing of TBB lower areas is a harbinger of strengthening and weakening of snowfall. Thunderstorms and hail occurred in the largest area of TBB gradient.The strengthening and weakening of TBB gradient indicate the emergence of thunderstorms and hail weather.The surface layer temperature of snowfall station is lower and the whole layer moisture conditions are better.There is moisture convergence center at the low-level. For snowfall station,the upward motion is strong,and there is low-level convergence and high level divergence field configuration. Hail stations have low-level inversion,with greater instability energy,middle dry cold air intrusion,upward motion weaker than snowfall area,there are low-level convergence and high level divergence field configuration.The height of 0 ℃ layer is around 3 km which is more conducive to occurring the large hail.Precipitation Station moisture conditions are good,but the degree of moisture convergence is weaker than snowfall area,the intensity of upward motion is almost the same as hail area,there is no low-altitude aerial convergence divergence field.