According to ATP-45. Warning And Reporting and Hazard Prediction of Chemical, Biological, Radiological and Nuclear Incidents[i], detailed weather information such as temperature, humidity, wind speed, wind direction, precipitation, and stability must be obtained to determine the effects of a CBRN hazard on the surrounding environment of the incident. Apart from the meteorological data, the impact of terrain should be considered.
The
direction and speed of an airborne cloud are influenced by the nature of the
terrain in the downwind area. Contaminant clouds can flow over rolling terrain,
down valleys, or around buildings in urban areas. In hollows, depressions, and
trenches dangerous concentrations may persist. The clouds can also encounter
obstacles such as hills and tend to be slowed down by the rough ground, tall
grass, and bushes. In the case of flat terrain, the movement of the
contamination cloud is even and steady. A real problem may appear in an urban environment,
where movement patterns may be very different, depending on buildings’ shape,
heights, and other factors. Additionally, when a predominant wind switches
direction in a matter of minutes, the situation becomes further complicated. In such circumstances and conditions, the cloud can be difficult
to predict and model[ii].
[i] ATP-45. Warning And Reporting and Hazard Prediction of Chemical, Biological, Radiological and Nuclear Incidents (Operators Manual) (2010).
[ii] Metodyka oceny sytuacji skażeń chemicznych, biologicznych i promieniotwórczych / Ministerstwo Obrony Narodowej. Szefostwo Obrony Przed Bronią Masowego Rażenia. Chem. 408/2013.