风的污染指数及其频率——城市总体规划中的一个气候学问题

长期来在城市总体规划中,总是按照“盛行风原则”把工业区布置在城市的下风侧,但却并不一定能达到预期的效果.本文阐明了“盛行风原则”的缺点,并自气候学的角度出发,综合考虑影响城市大气污染的各重要气象因素,提出了利用多年常规气象观测记录,计算风的污染指数和不同风向的污染指数频率的公式.按污染指数频率即可确定吹哪一个方向的风时可能出现大气污染的机率最大,从而可以按这一风向把工业区布置在城市的下风侧.

WIND POLLUTION INDEX AND WIND POLLUTION FREQUENCY——A CLIMATOLOGICAL PROBIEM IN URBAN PLANNING

The prevailing wind principle has long been adopted by urban planners, especially in the master plan stage. According to the principle, districts of industrial plants emitting air pollutants are located on the leeward of the city by prevailing wind, so that the urban air will not be polluted. But practi ce has proved that the principle is not alwaystrue. In this paper,the weakness of the prevailing wind principle is exposed and a new approach to the problem is proposed.It is pointed out that for the wind from any direction what determines the frequency of the occurrence of air pollution on the leeward of a given emissionsource is not the frequency of the wind but the frequency of tie occurrence of the weather conducive to air pollution associated with the wind. And the fact that the frequency of the prevailing wind is higher than that of the wind from other direction does not necessarily mean that the frequency of the occurrence of air pollution associated with the prevailing wind is higher than that associated with the wind from other direction.Therefore it is important for urban planners to find out the frequencies of occurrence of weather conducive to air pollution associated with winds from different directions. This can be done by using two. equations proposed in this paper. One is used to calculate the Wind Pollution Indeox by using routinely availabe meteorological data, which describes the level of air pollution with a given amount of air pollutants under the weather associated with the wind observed. The other is used to calculate statistically the Wind Pollution Frequency by using the data of Wind Pollution Idex, which describes the frequency of the weather conducive to air pollution associated with the winds from a given direction.