导致区域性雷暴大风天气的云型分类及统计特征分析

Classification and Characteristics of Cloud Patterns Triggering Regional Thunderstorm High Winds

利用2005—2011年的静止卫星、常规探空和重要天气报资料,文章选取了18次典型区域性雷暴大风过程,在分析500 hPa天气形势基础上对导致雷暴大风的强对流云型进行了分类分析,其发展过程可划分为初始、发展、成熟和消亡四个阶段。对静止卫星观测的定量特征分析表明,对流云团中IR1通道和水汽(WV)通道的亮温差基本为负值,其值的不断减小预示着强对流在持续发展;在监测和预报雷暴大风天气时,需要特别关注长椭圆形强对流云带的右侧和其右侧的孤立对流云团,尤其是TBB(红外亮度温度)低负值区、TBB高梯度区、IR1和WV通道亮温差值区及大梯度区均配合的区域。在定性分析的基础上对静止卫星IR1与WV通道的亮温特征进行了定量统计分析,获得了雷暴大风出现站点附近的红外亮温、水汽亮温、IR1与WV通道亮温差和红外亮温梯度的分布情况,结果发现大部分站点的雷暴大风天气出现在以下时段:红外亮温由急剧下降到平缓下降之间的过渡期;IR1与WV通道亮温差由迅速下降转为缓慢下降或稳定少变的时间点前后,且多数处于IR1和WV通道亮温差由正转负临近的时间段内;红外亮温梯度达到最大的时间点附近或开始下降的时候。

Based on the satellite data,observational data of upper-air and significant weather report from 2005 to 2011,the weather situation at 500 hPa and the cloud patterns of 18 processes of thunderstorm high winds are classified and analyzed.The development of cloud patterns can be divided into 4 stages:initial, growing,mature and dissipating.The brightness temperature difference between IR1 channel and water vapor channel is mostly negative,and the number’s decreasing indicates that the severe convective clouds are still developing.We need to pay more attention to the right part or the right single-cell storm of the elongated strong convective clouds when we monitor and forecast the cloud system of thunderstorm high winds,especially the low TBB areas,the high TBB gradient part and the area coordinating with the nega-tive area of IR1 and WV channel brightness temperature difference.Quantitative statistical analysis of the characteristic value are made on the basis of subjective analysis,and we get the distribution of the infrared brightness temperature,water vapor brightness temperature,channel brightness temperature difference and infrared brightness temperature gradient near the sites observing the thunderstorm high winds.We discover that the majority of thunderstorm high winds often take place during the period when the infrared brightness temperature develops from a sharp decline to a gentle decline and at the time point when the channel brightness temperature gently slows down or becomes stable.Moreover,most examples are near the time period when the channel brightness temperature difference changes from positive to negative,and at the point when the infrared brightness temperature gradient approaches the largest area or begins to decline.