利用非静力平衡中尺度模式WRFV3.2、NCEP 1°×1°再分析资料和常规观测资料,对2002年12月12～13日西安地区一次持续大雾天气进行阶段性数值模拟研究.结果表明,利用WRFV3.2模式能较好地模拟出大雾的范围、强度和生消过程,但模拟白天雾的强度较弱.这次大雾是平流辐射雾过程,在夜间的辐射降温和弱冷空气的入侵共同作用下,西安地区形成冷气垫,造成逆温产生,逆温的存在为大雾的产生和维持发展提供了有利的层结条件;地面湿度大,逆温层结稳定又有效地抑制了水汽向高空传输和能量交换,为大雾产生提供了充沛的水汽条件;在大雾产生和维持期间,微风有利于近地面的湍流交换,使辐射冷却作用扩散到适当高度,也可使水汽垂直输送到一定高度,有利于雾的产生和发展.而白天太阳短波辐射造成的逆温层抬升是引起大雾减弱和日变化明显的主要原因.%Based on the data of NCEP1 o × 1 ο reanalysis data and conventional observation, a long - lasting fog over Xi' an area in the winter of 2002 was simulated and diagnosed with WRF (Weather Research & Forecasting) non-hydrostatic model. Results indicated that it simulated successfully in evolvement of the fog,but the intensity in daytime was shorter than what was actually happening. The heavy fog was a typical advection-radiation fog. The radiation cooling at ground layer and the interaction of temperature advection were important to the establishment and maintenance of the inversion layer. The inversion at lower troposphere played a very important role in the long time maintenance of this fog event;stable stratification and very small wind speed at lower levels led to that water vapor could not diffuse timely,so there was abundant water vapor. The lifted inversion layer caused by solar radiation was the main reason for the weakness and obvious daily variation of this fog event.
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