VALMET: a valley air pollution model. Final report. Revision 1

Abstract

An air quality model is described for predicting air pollution concentrations in deep mountain valleys arising fro~ nocturnal down-valley transport and diffusion of an elevated pollutant plume, and the fumigation of the plume on the valley floor and sidewalls after sunrise. Included is a technical description of the model, a discussion of the model 1 5 applications, the required model inputs, sample calculations and model outputs, and a full listing of the FORTRAN computer program.

Atmospheric dispersion in mountain valleys and basins

“…valley atmosphere during the morning transition period. This thermodynamic model is also the basis of a valley-scale air pollution computer code (Whiteman and AIIwine, 1985), which predicts ground-level concentrations from the fumigation of elevated plumes to the surface during the morning transition period. The timing and duration of the morning transition period is dependent on the geometry of the valley, characteristics of the nocturnal inversion, surface cover, moisture content, weather, solar input, and time of year.…”

“…Winds continue downvalley in the stable core during the inversion breakup period, whereas, winds in the CBL below, and the region above often are upvalley during this same period. (Whiteman and AIIwine, 1985) Bader The daily behavior of the valley atmosphere from thermal effects can be divided into four time regimes, morning transition, daytime, evening transition, and nighttime (Whiteman, 1990). The morning transition period has already been described and illustrated in Thermally forced flows have been the focus of the discussion thus far.…”