摘要:
1982年4—7月对北京等地对流层低层晴天气溶胶数浓度、尺度谱分布进行了飞机观测。结果表明：来自西、西北和北部气团的气溶胶数浓度相当低（平均为10-1—100 /厘米3）。尺度谱分布用dn/dD=C/DA拟合，相关显著水平α≤0.01，幂指数A值多小于3（占总数73%以上），比Junge给出的A=4值小些。鉴于直径D=0.5—2微米粒子在大气中的重要性，也按dn/dD=C′/DB进行拟合，多数测值α≤0.01，少数α≤0.05。幂指数A、B和D=0.5—1微米粒子相对数浓度f1在水平、垂直方向上是相当均匀稳定的。受城市影响时，混合层内气溶胶数浓度明显增大，尺度谱分布斜率变陡（A、B增大），特别是和“气-粒”转化有关的D=1微米左右粒子数浓度增加非常显著，比不受城市影响时，增加了1—2个量级，最大可增加3个量级。可见，城市影响是造成混合层气溶胶数浓度增大、尺度谱分布变陡、局地大气污染加重、低层能见度变坏的重要原因。
Abstract:
Clear air aerosol number concentration and its number/size spectrum distribution in the lower troposphere were observed by a airborne instruments in Beijing etc. during April—July in 1982. Results show that the aerosol number concentration of the air coming from west, northwest and north are rather low (10-1—100cm-3 on the average). The number/size distribution has been fitted by =C/DA, with the correlation significance level α≤0.01, most exponential A values are less than 3. Because of the importance of the diameter 0.5 to 2μm particles in the atmosphere, its number/size distribution has also been by =C/DB. It is found that the correlation significance level isα≤0.01 for the most observations, andα≤0.05 for a small parts. The values of A, B and smaller particles (0.5≤D≤1μm) relative number concentration f1 are fairly uniform and steady both is horizontal and vertical direction. When effected by city, the aerosol number concentration in the mixing layer increase evidently, the number/size spectrum distribution is steeper and especially for the smaller particles (D~1μm) the concentration is very remarkable, therefore city effect is a important cause for high aerosol concentration, steep number/size distribution, strong local air pollution and low visibility in mixing layer
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