2006年冬季在南京北郊盘城利用系留气球探测系统、自动气象站等仪器对雾日和非雾日的边界层进行了监测,对比分析了两者的边界层结构。结果表明,非雾日主要为单层贴地逆温,并时常出现短时的双层结构,雾发展成熟时逆温则脱离地面。与非雾日相比,雾日平均雾顶之上温度日较差增大,雾顶之下则减小。平均风速的时间—高度分布在雾日和非雾日类似,在稳定性边界层中风速随高度出现一个或者两个极大值区。温度和比湿在非雾日没有显著的对应性,而在雾体内具有较好的对应关系,在雾顶升降过程中反相关。较强的逆温、较低的温度和较小的近地层风速是南京冬季成雾的背景条件。
An observation was carried out in the winter in 2006 at Pancheng,northern suburb of Nanjing,using tethered balloon system,automatic weather station and other instruments.The boundary layer structures on fog and fog-free days are analyzed and compared.Results show that on the fog-free days the temperature inversions are mainly single-layer ones,sometimes with short duration double-layer structures,while the fog mature stage inversions are free from the ground.Compared with the fog-free days,the temperature diurnal range above the average fog top on fog days is larger while the below one is smaller.The time-height cross section of average wind speed on the fog days is similar to that on the fog-free days.In the stable boundary layer,the wind speed profiles have one or two maximum values.The average wind speed profiles on fog days are similar to those on the fog-free days.No remarkable relationship exists between the temperature and specific humidity profiles on the fog-free days.Differently,these two parameters have a good correspondence between each other in the fog body whereas they vary oppositely during the ascent and descent of the fog top.The stronger temperature inversion,lower temperature and smaller near-surface-layer wind speed are background for the winter fog formation in Nanjing.