Characterizing the dispersive state of convective boundary layers for applied dispersion modeling

Abstract

Estimates from semiempirical models that characterize surface heat flux, mixing depth, and profiles of temperature, wind, and turbulence are compared with observations from atmospheric field studies conducted in Colorado, Illinois, Indiana, and Minnesota. Sodar observations are compared with tower measurements at the Colorado site, for wind and turbulence profiles. The median surface heat flux, as calculated using surface-layer flux-profile relationships and an energy budget model, was consistently overestimated by 20 to 80%. Several mixing-depth models were evaluated: (1) integration of the hourly surface heat flux and friction velocity, (2) solving for the time rate of change of profiles of virtual potential temperature, and (3) an interpolation scheme used by the U.S. Environmental Protection Agency in regulatory dispersion models. For the late afternoon, 80 to 90% of the estimates from the first and third models were within 40% of the observed values. For the morning hours after sunrise, all were less accurate. Temperature estimates from surface-layer flux-profile relationships compared well with observations within the mixed layer, but were too low for the inversion layer aloft. Wind profiles were derived using surface-layer flux-profile relationships, a windprofile power-law based on Pasquill stability category, and sodar measurements. The sodar measurements were superior to both types of model estimates. Turbulence profiles were derived from sodar measurements and from semiempirical similarity relationships based on mixing depth and Obukhov length. The scatter in the comparisons with the sodar observations is twice that seen in the comparisons with empirical profile relationships. Overall, it appears that uncertainty of as low as 20 to 30% in the characterization of the diffusion meteorology is the exception rather than the rule.

Description and validation of ERAD: An atmospheric dispersion model for high explosive detonations

“…The boundary layer parameterization used in ERAD is based on scaling theory. Formulas similar to those presented here have been suggested by Wilczak and Phillips (1986), Gryning et al (1987), Irwin and Paumier (1990) and Hanna and Chang (1992). Parameterizations of this type have accuracies of 20 to 30% over a broad range of meteorological conditions.…”

Laboratory simulations of the atmospheric mixed-layer in flow over complex topography

“…Techniques for estimating z i in horizontally homogeneous terrain include Holzworth 1964, (Holzworth 1967), Irwin and Paumier (1990), Raynor and Watson (1991), Batchvarova and Gryning (1991), and Weil et al, (1997). The adjustment of z i with flow over and around irregular terrain has received much less attention.…”

Μοντέλα Διακίνησης Και Εναπόθεσης Στερεών Σωματιδίων Ιπτάμενης Τέφρας Στο Περιβάλλον Και Συνακόλουθες Ραδιολογικές Επιπτώσεις Στην Λεκάνη Της Μεγαλόπολης

“…• Ο αναγνώστης ϑα µπορούσε επίσης να δει δύο δηµοσιεύσεις, οι οποίες κάνουν ανασκόπηση σε υπολογιστικές µεθόδους εκτίµησης του ύψους ανάµιξης καθώς και σε µεθόδους, που ϐασίζονται σε µετρήσεις στα ανώτερα στρώµατα της ατµό-σφαιρας : Η πρώτη είναι αυτή των Irwin and Paumier [92] και η δεύτερη εκείνη των Seibert et al [168].…”