青岛地区降雪时空特征及环流成因分析

为了研究青岛地区的降雪特点及形成原因,使用1961—2009年实况观测及NCEP全球再分析格点资料,统计分析了青岛地区降雪的时空特征,并采用合成分析和物理量诊断的方法对青岛大雪进行了环流分型和物理量特征分析。结果表明:青岛地区降雪最早月份11月,最晚月份4月。年平均降雪量10 mm左右,东北和西南多、东南少;年平均降雪日数10天左右,西北多、中部少。月平均降雪量、降雪日数均呈中间高、两头低的月际变化特征,12月、1月、2月多,11月和4月少。小波分析表明,年降雪量和降雪日数均存在19年左右的周期。大雪最早出现在11月下旬,最晚3月中旬。大雪的环流形势分为冷槽东移型、平直环流型和横槽转竖型3种,主要环流形势为冷槽东移型;高空明显的冷空气入侵,地面冷暖空气交汇,低层水汽供应充分,湿度大,低层辐合、高层辐散,引发青岛地区明显的降雪天气。物理量特征分析给出了青岛大雪预报的一个预报着眼点。

Snowfall: Temporal and Spatial Characteristics and Circulation Cause in Qingdao

To study the snowfall characteristics in Qingdao and the formation causes, the NCEP global reanalyzed grid data and observational data of 1961-2009 were employed to analyze the temporal and spatial characteristics of snowfall in Qingdao. Using the method of composite analysis and physical diagnosis, the circulation patterns and physical characteristics of the Qingdao heavy snowfall were obtained. The results showed that: the earliest snowfall in Qingdao was in November, the latest was in April; the average annual snowfall was around 10 mm, more in the northeast and southwest, and less in the southeast in Qingdao; the average annual snowfall days were about 10 days, more in the northwest, and less in the middle; the monthly average snowfall and snowfall days showed the monthly variation characteristics of high in the middle and low at both ends, more in December, January and February, and less in November and April; the wavelet analysis results showed that both annual snowfall and annual snowfall days had the characteristics of oscillations with a quasi-19 year period; heavy snow first appeared in late November and the latest was in the middle of March. There were three kinds of circulation patterns for heavy snow in Qingdao, which were cold-trough eastern moving pattern, straight circulation pattern and zonal trough shifting to meridional pattern, and the main pattern was cold-trough eastern moving pattern; there were obviously cold air in the upper air and confluence of cold and warm air on the ground in Qingdao, meanwhile the warm air carried abundant moisture and the humidity increased. Qingdao was in the divergence area in high-level and convergence area in low-level. Such circumstances caused significant snowfall weather in Qingdao. Thus, physical characteristics analysis could enhance the heavy snow forecasting in Qingdao.