摘要
利用常规资料、NCEP1°×1°再分析资料及多种新型探测资料,对北京地区2011年深秋初冬季节预报接连失误的11月29日和12月2日两次降雪天气过程进行了分析。结果表明:①11月29日,在地面偏东风配合倒槽的有利形势下北京未出现降雪的重要原因之一是偏东风为干冷性质,且层次深厚,北京边界层湿度条件差。对流层低层冷空气快速南压填塞倒槽是预报出现失误的另一重要原因。②12月2日降雪过程,925hPa的切变线和地面锋面为边界层的水汽辐合抬升提供了动力条件,对流层中下层的水汽输送为降雪提供了水汽条件。③对比研究表明,北京地区冬季降雪预报要特别关注边界层湿度的变化,当边界层内水汽条件较差时,即使中高层有明显的天气系统也不易产生降雪。当边界层湿度条件好,并配合有边界层辐合系统时,即便对流层中层没有明显天气系统,也会产生降雪。
Unsuccessful forecasting for two snowfall processes in Beijing in 2011 is analyzed by using a variety of high spatial-temporal resolution observation data,NCEP1°× 1°analysis data,and conventional observation data.The result shows：（1） On 29 November 2011,one of the most important reasons that there was no snow in Beijing is that the east winds in Beijing were dry and cold in a deep layer,and the boundary layer moisture condition was unfavorable.The cold air moved southward,leading to a filling pressure trough in the lower troposphere,which is another important reason for the fault prediction.（2） In the process of snowfall on 2 December 2011,the front and 925 hPa shear line provided dynamic condition for uplifting boundary layer water vapor convergence,and the lower troposphere water vapor transmission provided the moisture condition for snow.（3） Comparative analysis shows that more attention should be paid to water vapor change in the boundary layer in snow forecasting in Beijing.It hardly snows even if there is obviously favorable weather pattern but poor water vapor condition in the boundary layer; it probably snows if there is good moisture condition and convergence in the boundary layer,even if there were no favorable weather systems in the middle troposphere.
出处
《气象科技》
2014年第3期488-495,共8页
Meteorological Science and Technology
基金
2011年度城市气象科学研究基金(IUMKY&UMRF201105)
国家支撑项目"城市群高影响天气的特征和成因分析"(2008BAC37B01)
公益性行业(气象)科研专项(GYHY201006010)资助
关键词
降雪过程
物理量场
边界层湿度
华北锢囚锋
snowfall
physical quantity field
PBL humidity
North China occluded front
