2007—2010年北京自动站浓雾特征分析与临近预报初探

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1000 m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.

Characteristics and Nowcasting of Thick Fog in Beijing

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.