MDIFF is a transport and dispersion model built to handle accidental
gaseous releases at DOE's Idaho National Laboratory. MDIFF is
incorporated into the INLViz display system that is used for emergency
response at the INL.
MDIFF is based on the well known MESODIF puff dispersion model, the
grandfather of many transport and dispersion models in use around the
world today. MESODIF was one of the first puff diffusion models ever
developed for use on modern computers and was developed right here at
The puff transport algorithm is conceptually very simple: 1)
every release of material is represented as a series of puffs, 2) each
puff is allowed to move and grow independently, and 3) concentrations
are calculated as the sum of the concentrations due to all of the
MDIFF is used to model short-term episodes. It operates using
five-minute data from the INL Mesonet. The model does have some
limitations and is showing its age. It lacks certain features such as
deposition, radiological dose computations, and the ability to account
for vertical wind shear. These features could have been added to
MDIFF, but ARLFRD decided that it made more sense to transition to the
more widely used NOAA HYSPLIT model instead. This would leverage
ARLFRD's limited staff resources by interfacing with a much larger
HYSPLIT community. MDIFF will continue to be available during the
transition to HYSPLIT.
More information about MDIFF is contained in a NOAA Tech. Memo available here.