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• 基金项目：

• 张锡福
• 中国科学院大气物理研究所

• 赵翼浚
• 中国科学院大气物理研究所

• 邹孝恒
• 中国科学院大气物理研究所

• 陈泮勤
• 中国科学院大气物理研究所

• 贾新媛
• 中国科学院大气物理研究所

• 杨锦德
• 中国科学院大气物理研究所

• 邓玉珍
• 中国科学院大气物理研究所

• 李军
• 中国科学院大气物理研究所

• 摘要：在北京北郊铁塔的100m高度释放六氟化硫（SF₆）气体（每小时排放30—40kg）,在下风方向3、5km两条弧线上用一辆汽车往返穿行,在车上用塑料针筒取样,然后回到实验室分析浓度。在9、20km弧上和36、50、70km的弧上分别各用一辆汽车装载连续示踪物检测仪穿行,当时在记录器上记录浓度的空间分布。 根据实验资料并配合计算的100、50m和地面的水平轨迹及其它气象资料,分析了风速垂直切变、水平风摆动、大气稳定度和地表特征等因子对扩散的影响。风速垂直切变（特别是地形风和城市热岛引起的风速垂直切变）使浓度水平分布分裂为几段。而在切变较小的稳定和中性条件下,在36km距离的浓度仍呈现典型的正态分布。 计算了水平扩散参数σy,得到城区和郊区的两种稳定度下（中性和稍不稳定）几十公里距离的σy随距离的变化。其规律与用平衡球定位方法所得到的结果接近,并与国外同类实验结果进行了比较。

• Abstract：SF6 was released at a height of 100m from a 325m tower, with a rate at 30-40kg/hr. Samples were collected manually by using plastic syringes in a car running along 3-km and 5-km arcs and returned to laboratory followed by gas chromatographic determination. SF6 concentrations downwind at 9-, 15-, 20-, 36-, 50- and 70-km arc were real-time values detected by two continuously operated perfluoro-carbon sniffers, each mounted in an automobile. One of the automobiles was running along 9-km and 20-km arcs and the others along 36-km and 70-km arcs.Based on the SF6 concentration data, the three horizontal level trajectories (surface, 50 m, 100 m) and other meteorological data, influences on meso-range atmospheric diffusion by vertical shears of wind speed and direction, wind meandering, effects of ground surface and atmospheric stability were analysed. Especially the concentrations at 36km (unstable) or at 70 km (neutrally stable)were split into several parts under strong wind speed shear caused by topographical wind and thermal island circulation. But the concentrations are of a typical Gaussian shape in homogeneous and stable wind field.Horizontal spread σy as function of downwind distance in urban andsuburban area at neutral and unstable condition were obtained and found fitted into the σy curves calculated by use of balanced balloon data.

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