Tropospheric dispersion: The first ten days after a puff release

Abstract

Dispersion from a puff released in the atmospheric boundary layer in mid‐latitudes is simulated with a Lagrangian global multiple‐particle model using analysed three‐dimensional wind fields. Quantitative measures of the spread are computed and used to assess the influence of the synoptic system into which the puff is released, and the ways in which turbulent diffusion can contribute to the total spread. the nature of the dispersion over ten days is examined to elucidate the controlling meteorology and kinematics during the various phases which could be identified. the results are compared with measurements made from constant‐level balloons. A time index is proposed to characterize large‐scale dispersion from a point source.

Subgrid‐scale treatment for major point sources in an Eulerian model: A sensitivity study on the European Tracer Experiment (ETEX) and Chernobyl cases

“…In particular, emissions from major point sources are badly represented by Eulerian models since they are usually assumed to mix immediately within a grid cell, whereas a typical point‐source plume (e.g., from a power plant) does not expand to the size of the grid cell for a substantial time period. This leads to an unrealistic near‐source modeling, especially since the K‐theory approach often used in Eulerian models does not properly represent the diffusion in the vicinity of the source [ Maryon and Buckland , 1995]. Numerical problems can also be raised, such as oscillations caused by strong gradients due to point sources [ Brandt et al , 1996], if a nonmonotonic advection scheme is used.…”

Physical atmospheric structure and tropospheric mixing information in vertical profiles of atmospheric CO2 mixing ratios

“…The turbulent flow of a plume can be typified considering by the relative dispersion of Lagrangian particles [ Maryon and Buckland , 1995; Huber et al , 2001; Colette and Ancellet , 2006]. The root‐mean square (rms) distance in time , σ r (t) , is defined relative to the average position of the plume as: where N is the number of particles, and d i (t) is the distance of each particle from the center of the plume at time t (counted forward), considering both the meridional and zonal separations.…”

“…The finite‐time Lyapunov exponent describes the stretching processes in the atmosphere given the following expression [ Maryon and Buckland , 1995; Cohen and Kreitzberg , 1997; Stohl , 2001; Huber et al , 2001; Colette and Ancellet , 2006] where Δ r(0) is an arbitrary horizontal distance between particles at the initial point and Δ r(t) is their distance after a time t (counted forward) accounted as the standard deviation distance of particles from the mean position of the plume; and τ is the characteristic timescale of the dispersing eddies, called typical eddy turnover time. If at any time λ > 0, we say that the system is chaotic [ Pierrehumbert and Yang , 1993].…”

“…[7] The turbulent flow of a plume can be typified considering by the relative dispersion of Lagrangian particles [Maryon and Buckland, 1995;Huber et al, 2001;Colette and Ancellet, 2006]. The root-mean square (rms) distance in time, s r (t), is defined relative to the average position of the plume as:…”

Comparison of atmospheric aerosol backscattering and air mass back trajectories

“…International protocols are in place for the management of such emergencies, and extensive collaborative work has been carried out on the testing and intercomparison of transport and dispersion models (for example, Mosca et al, 1998). Transports of airborne pathogens, and biota in general, also require suitable transport and dispersion models which, in brief, have been applied to pollution problems and the physics of atmospheric dispersion on all motion scales from street canyons to global diffusion (Maryon and Buckland, 1995). A second area of aerosol and gaseous transport studies of pressing importance is concerned with the evolution of climate forcing and change, in which sulphate aerosol and volcanic ef¯uent are just two of a range of airborne substances subject to intensive investigation, typically involving general circulation models.…”