Dispersion modelling is a key element of most odour assessments around the world. There are 2 or 3 well known dispersion models developed for regulatory assessments of which the most well-known are, AERMOD and CALPUFF. Because both models have been US EPA guideline models until CALPUFF was recently removed in 2017, they are routinely used in most air quality and odour assessments.

   This article highlights the history and background behind CALPUFF and, the reason for its removal as a US EPA guideline model. Concerns with AERMOD for odour assessments will be presented in a separate document, Part 2.

Jennifer Barclay

Atmospheric Science Global (ASG). Auckland, New Zealand

   The 4th Graz Lagrangian Model - GRAL User Workshop will be held in Innsbruck, Austria, on 12 – 13 March 2019. This recent lagrangian model is offered with a free GUI available in both Linux and Windows and has a special module focused on odour dispersion modelling. The workshop aims at giving an overview about all new developments, and it offers a distinct possibility for an informal exchange with other users and their specific experiences.This workshop is free.

 The Graz Lagrangian Model - GRAL - was initially developed in 1999, and has been used extensively in regulatory assessments and scientific studies. The initial driver for the development of GRAL was the need for a model that could deal with the frequent low-wind-speed conditions (< 1.5 m s^-1 for up to 90 per cent of the time) in the inner-Alpine basins of Austria. Some papers have recently being presented that compares the use of the GRAMM/GRAL in some odour emitting facilities. This software is freeware, but the code is unfortunately closed.