Nocturnal Wind Structure and Plume Growth Rates Due to Inertial Oscillations

Abstract

Theoretical plume growth rates depend upon the atmospheric spatial energy spectrum. Current grid-based numerical models generally resolve large-scale (synoptic) energy, while planetary boundary layer turbulence is parameterized. Energy at intermediate scales is often neglected. In this study, boundary layer radar profilers are used to examine the temporal energy spectrum, which can provide information about the atmospheric structure affecting plume growth rates. A boundary layer model (BLM) into which the radar information has been assimilated is used to drive a Lagrangian particle model (LPM) that is subsequently employed to examine plume growth rates. Profiler and aircraft data taken during the 1995 Southern Oxidants Study in Nashville, Tennessee, are used in the model study for assimilation and evaluation. The results show that the BLM without assimilation significantly underestimates the strength of the diurnal?inertial spectral peak, which in turn causes an underestimate of plume spread. Comparison with measures of plume width from aircraft data also shows that assimilation of radar information greatly improves plume spread rates predicted by the LPM.