During a crisis, the commando post needs to have access to relevant information in order to estimate which product has been released, what amount of it has been liberated (sometimes the maximum possible amount is taken but this can lead to largely overestimated unrealistic security measures), where the pollution actually is and where it goes to. In the case of gaseous elements, the cloud is mostly invisible making it very hard to locate it. For liquids leaking in the ground, it is very important to know when the substance will meet the aquifer and which drinking water facilities can be affected. What is the time frame in which one has to react in order to preserve critical water bodies ?

It is important to note that during a crisis, pollution measurements are an essential part of the safety procedures. No decisions and/or actions are taken solely on the basis of model calculations! Therefore, it is very important to know which products have been released so that the measurement teams can use the relevant sensors/equipment. For the moment, some fire brigades are well organised and have already a network of pre-defined measurement locations. In case of transport accidents, this is of course less evident.

In conclusion, during the response phase:

a) atmospheric model calculations are mainly used to:

Ö         estimate the shape of the plume (the absolute values are adjusted to reach an agreement with the measured values) and to help field actors to place sensors at relevant positions.

Ö         estimate the time evolution of the plume, i.e. forecast where the plume will be after 30 minutes, after 1 hour, etc.

b) recent satellite information can be used to have up-to-date information about the site (land cover, roughness of the surface, unknown access roads to the site, ...) as input to the atmospheric dispersion model and for visual aid.