南京北郊低空污染气象条件若干特征

THE FEATURES OF THE METEOROLOGICAL CONDITIONS FOR LOW-LEVEL POLLUTION IN NORTHERN SUBURBS OF NANJING, CHINA

本文根据南京北郊大厂镇地区实测低空温风资料的统计分析,揭露了该区低空逆温、混合层顶高度、风向、风速、大气稳定度等的铅直分布规律和局地环流的某些特征。

In this paper, the meteorological conditions for low-level pollution in the district situated in the northern suburbs of Nanjing, China, a base of chemical industry, are analyzed. Some major conclusions are reached as follows:1. The frequency of inversion in the district is the highest in autumn and winter. The thickness and intensity of inversion are at their maximun in winter.2. The atmospheric stability tends to become neutrally stratified as altitude increases. However, stable stratification is still observed at higher levels in winter. The frequency of stable stratification can reach as high a value as 47% during the day in winter, especially at heights of 200-300m. Obviously, this has much to do with the frequency inversion.3. The mixing depth is the smallest in winter and after midnight till early morning in day. It is only about 444m.4. Wind speed increases as height goes up and obeys the exponential law u2 = u,(z/z,)a within 300m above the ground.The exponent a varies between 0.05-0.42, depending on stability. Wind direction turns to the right as altitude increases. The deflective angle is bigger in winter than in summer. On the average, the deflective angle is 22.5° within 125m above the ground.5. By gradient wind, pilot balloon and tetroon drifting locus observations. There seem to be a local circulation in the area. The authors hold that this probably results from the combined thermodynamic difference between town and country and complex terrain in the district. It needs further investigation and research