Atmospheric Dispersion Modelling

The Prairie Grass data set[]

Basic information on the data set[]

The Prairie Grass experiment is a classic experiment conducted in July-August 1956. A release took place from a point source close to ground level (46 cm height). SO2 was used as a tracer, and concentrations were measured on arcs at distances of 50 m, 100 m, 200 m, 400 m and 800 m. The duration of each of the 68 sampling periods was 10 minutes. The original data were published in a paper report (Barad, 1958).

Many researchers have used the data, but there is no official, digital version of the data.

Experiences with the data set[]

There is a total of 68 runs (10-minute sampling periods) from the months of July and August. 4 runs had a non-standard release height. A subset of 4 experiments: no. 3, no. 4, no. 13 and 14 - deserve special treatment. These runs are very stable and the meteorological data are not well-behaved. Thus, whereas roughness length z0 is found to be around 6 mm in general, for these 4 runs an estimate based on wind profile data gives a roughness length that is more than 10 times as large. When using AERMOD and to some extent OML the subset of these 4 runs result in very large modelled concentrations. See the conference paper by Olesen et al. (2007) for more details.

Availability of the data set and access to validation studies[]

  • A package with materials concerning the ASTM Standard Guide for Statistical Evaluation of Atmospheric Dispersion Models, D6589-00 includes the Prairie Grass data set. This material is available through
  • Here is a link to a page at NERI in Denmark, which gives technically minded readers the possibility to explore the Prairie Grass data set and compare data with model behaviour. A group at the National Environmental Research Institute (NERI) in Denmark have used the Prairie Grass data to study model performance. They have rearranged the data sets into an Excel workbook with embedded graphs and macros, and further added model results from the Danish OML model and the US AERMOD model. The user can step through the various runs and inspect concentration results according to measurement and models. The Excel workbook is available for download. See the above mentioned page.
  • The Atmospheric Transport and Data Archive website provides most of the Project Prairie Grass data in digital format. All three of the original data volumes are available in pdf format. This material is available at Atmospheric Transport and Data Archive - Tracer data sets (


Barad, M.L., 1958: Project Prairie Grass, a field program in diffusion. Geophys. Res. Pap. 59. Air Force Cambridge Centre.

Olesen, H.R., Berkowicz, R., Løfstrøm, P., 2007: Evaulation of OML and AERMOD. 11th International conference on Harmonisation within Atmospheric Dispersion Modelling for Regulatory Purposes, Cambridge, July 2-5, 2007. 5-page extended abstract at