2007—2010年北京自动站浓雾特征分析与临近预报初探

Characteristics and Nowcasting of Thick Fog in Beijing

为探索北京地区浓雾天气特征和临近预报方法,分析了北京2007—2010年18个道面自动站能见度1000m以下的天气资料。结果表明:①浓雾具有明显的日变化和年变化。05:00—09:00是高发时段,12:00—18:00是低发时段。全年浓雾主要集中在9-12月,6、7月最少。②空间分布上,呈现"东南多,城区少"的特征,统计80%以上的浓雾都发生在大兴和通州。③浓雾变化具有突发性和象鼻形先期振荡的特征。④浓雾能见度变化与气象要素变化关系密切。偏南风和偏东风最有利于浓雾生成发展,西北风最有利于浓雾的消散。风速减小,气温下降,湿度增大,能见度降低,浓雾生成和发展;风速增大,气温升高,湿度减小,能见度上升,浓雾减弱消散,但湿度的减小滞后于能见度的上升。浓雾维持阶段,要素变化都很小。

Based on the observation data provided by the automatic meteorological stations for road weather information in Beijing, the characteristics of low-visibility thick fogs and the method of nowcasting are studied. The main conclusions are as follows： （1） The thick fog with the visibility below 200 m happens mostly between 05：00 to 09：00, from September to December, and lest between 12：00 to 18：00, from June and July. （2） About 80 ~ of thick fog cases with visibility below 200 m appears in Daxing and Tongzhou districts in the southeastern Beijing, and seldom in downtown. （3） Before the formation of thick fogs, there was a thick-thin-thick fluctuating pattern in visibility variation. （4） The visibility changes with the wind, temperature, and relative humidity; the south and east wind is advantageous to the formation of thick fogs; the northwest wind is advantageous to their dissipation. During the development period of thick fogs, wind speed becomes slow; relative humidity rises; temperature reduces; and visibility becomes lower. During the maintain period, the wind speed, relative humidity, temperature, and visibility all change slightly. During its dissipation period of, the wind speed becomes big; relative humidity reduces; temperature rises; and visibility becomes bigger; but the reduction of relative humidity is later than the rise of visibility.