AN ANALYSIS OF THE ASYMPTOTIC-BEHAVIOR OF CROSS-WIND-INTEGRATED GROUND-LEVEL CONCENTRATIONS USING LAGRANGIAN STOCHASTIC SIMULATION

This paper examines the asymptotic behavior as a function of downwind distance of ground-level cross-wind-integrated concentration (CWIC) ca used by a continuous ground-level source in the atmospheric surface la yer. We first present asymptotic expressions obtained from an analysis of data from Project Prairie Grass (PPG, Barad, 1958), and then deriv e corresponding formulae from data generated using Lagrangian stochast ic (LS) model simulations. Under stable and neutral stratification, th e formulae derived from PPG data agree well with that from LS simulati ons. Assuming that the Lagrangian stochastic model represents current understanding of dispersion, this agreement suggests that the formulat ions for stable and neutral conditions are credible. On the other hand , for unstable stratification, we find that while the LS model yields a ''-- 3/2'' law, the PPG data suggest a fall-off with distance that i s closer to a ''-- 2'' slope. At the present time, we cannot identify the reasons for this disagreement. (C) 1997 Elsevier Science Ltd.