Alongwind dispersion - A simple similarity formula compared with observations at 11 field sites and in one wind tunnel

Observations of alongwind dispersion of clouds were collected from 11 held sites and from one wind tunnel and were used to test simple similarity rela tions. Because most of the observations consist of concentration time serie s from fixed monitors, the basic observed variable is sigma (t), the standa rd deviation of the concentration time series. The observed sigma (t)s rang e from 0.3 to 9000 s. The concentration rime series observations also allow the travel time t from source to receptor to be estimated, from which the cloud advective speed u(e) can be determined. Observed is range from 2 to 4 0 000 s, and observed u(e)s range from 0.5 to 16 tn s(-1). The alongwind di spersion coefficient sigma (x) is then calculated from u(e)sigma (t). The r esulting sigma (t) and sigma (x) observations support the similarity relati ons sigma (t) = 0.1t and sigma (x) = 2u(*)t, where u(*) is friction velocit y. About 50% of the observations are within a factor of 2 of these similari ty relations.