Portal de Periódicos da CAPES

Chapter 2.16 Medium-range puff growth

2007; Elsevier BV; Linguagem: Inglês

10.1016/s1474-8177(07)06216-x

1474-8177

Torben Mikkelsen, Søren Thykier-Nielsen, Steen Cordt Hoe,

Atmospheric aerosols and clouds

For decision support to emergency management organizations dealing with accidental or intentional releases of hazardous materials, being nuclear, chemical, or biological of nature, puff models with parameterized horizontal and vertical dispersion coefficients, σxy and σz, respectively, are advantageously used to provide fast real-time predictions of the potential downwind hazards. On the local scale (defined as the range 0–20 km downwind from the source point) the dispersing puff's sizes are typically smaller than, or of the order of ∼1 km, and “standard” similarity scaling of the puff dispersion is well established (Mikkelsen, T., Thykier-Nielsen, S., Astrup, P., Santabárbara, J.M., Sørensen, J.H., Rasmussen, A., Robertson, L., Ullerstig, A., Deme, S., Martens, R., Bartzis, J.G., Päsler-Sauer, J., 1997. MET-RODOS: A comprehensive atmospheric dispersion module. Radiat. Prot. Dosim. 73, 45–56; Thykier et al., 2004). Beyond the initial stage, however, starting say at travel distances beyond the 10–20 km range from the source point, the puffs vertical extent will often be limited by the mixing height, while their horizontal growth will be influenced by the synoptic scale turbulence. For dispersion at travel times t larger than the Lagrangian time scale tL, Mikkelsen and Pecseli (1987) originally suggested, on dimensional grounds: σxy(t)=cε1/2(tLt)3/4 Here, ε (0.0005 m2 s–3) is a bulk tropospheric dissipation rate estimated from the spectral observations of Nastrom and Gage (1985) and tL a single tropospheric Lagrangian time scale estimated from the Coriolis parameter f−1∼104 (s). In this paper, the “medium-range puff formula” is re-derived more rigorously from a spectral model of turbulent puff diffusion. The parameterization has subsequently been implemented in the real-time puff dispersion model RIMPUFF (Thykier-Nielsen et al., 2004>) for practical use with real-time emergency management of several real-time decision support systems of today, e.g., RODOS (Mikkelsen et al., 1997) and ARGOS (Schou-Jensen, L., Pehrsson, J., 2007. Argos Whitepaper www.pdc.dk/argos. Prolog Development Center A/S H.J. Holst Vej 3C-5C, DK 2605 Brøndby, Denmark.). The proposed sigma-formula comes into play for mid- and long-range dispersion calculations, that is, for calculation of puff growth when the horizontal puff size is bound within the range:∼1 km<σxy<∼400 km.