Meaning of Diffusion Parameters and Significance of Turner Charts and Some Comments on their Adoptation

Abstract

The meaning of parameters σ_y and σ_z which appear in conventional diffusion formula is considered. Though σ_y is equal to standard deviation which can be calculated from concentration distribution, σ_z cannot be directly derived from the distribution. So the meaning of σ_z, is diffusion parmeter, but not statistical quantity such as standard deviation. The Turner charts show σ_y and σ_z against travelling time t, but the Pasquill charts show these parameters against leeward distance x. Comparing both charts, Turner's and Pasquill's, the Turner charts correspond to the Pasquill ones when wind speed is 6m/s. From the above consideration on the meaning of parameters, the Turner charts which are independent of wind speed have no general significance, and when the wind speed is u, the values of the parameters should be multiplied by √u/6.