Summary

This scientific review concerns a qualitative analysis of state-of-the-art within the description of the governing processes for emission, dispersion, transport, transformation and deposition of atmospheric nitrogen compounds. The analysis is made with the aim of evaluating on an international level the Danish model tools for describing local deposition of atmospheric nitrogen.

 

The Danish model tools for deposition of atmospheric nitrogen will from now on be NERI’s model system DAMOS (Danish Ammonia Modelling System), which is based on the local scale model (OML-dep) coupled to a long range transport model. The long range transport model is currently NERI’s Lagrangian model ACDEP (Atmospheric Chemistry and Deposition) Model, but a shift to NERI’s Eulerian model DEHM-REGINA is in progress. In this scientific review there is thus made a qualitative evaluation of these three model with respect to international state-of-the-art.

 

The qualitative analysis in the scientific analysis may be summarised by the two tabels for respectively long range transport (ACDEP and DEHM-REGINA) and local scale description (OML-dep).

Comparison of  ACDEP and DEHM-REGINA with state-of-the-art within regional models for this area.
	State-of-the-art	ACDEP	DEHM-REGINA
Emission	16 km x 16 km dynamical seasonal variation	16 km x 16 km dynamical seasonal variation	16 km x 16 km – semi- dynamical seasonal variation
Transport	Eulerian 2-way nesting	Trajectories	Eulerian 2-way nesting
Particles	In size distributions	Strongly parameterised	Strongly parameterised
Chemistry	Explicit gas phase, wet phase and particle phase chemical schemes	Reduced chemistry  (CBM-IV) – strongly parameterised particle and wet phase chemistry	Explicit gas phase chemistry (56 compounds and 150 reactions) - strongly parameterised particle and wet phase chemistry
Wet dep.	Full wet phase chemistry for cloud and rain drops	Incloud & below cloud scavenging coefficients	Incloud & below cloud scavenging coefficients
Dry dep.	Resistance method with seasonal variation in surface resistance	Resistance method – no seasonal variation in surface resistance	Resistance method – strongly parameterised seasonal variation of surface resistance

 

Comparison of OML-dep with state-of-the-art within local scale models in this area
	State-of-the-art	OML-DEP
Emission	Farm level – dynamical seasonal variation	Farm level – dynamical seasonal variation to be implemented
Transport	Detailed plume calculation – mainly complex description in CFD models	Standard Gaussian plume calculation
Particles	No particles	No particles
Chemistry	Strongly parameterised first order chemistry	No chemistry
Wet dep	No wet dep.	No wet dep.
Dry dep.	Resistance method with seasonal variation in surface resistance	Resistance method – Non seasonal variation in surface resistance

 

NERI’s Lagrangian ACDEP model is no longer state-of-the-art within long range transport-chemistry models. The change to the more modern Eulerian model DEHM-REGINA is therefore natural. DEHM-REGINA represents next generation of models in this field and is current state-of-the-art, although there are still room for improvements. This concerns e.g. the newly developed description of seasonal variation in NH3 emissions that has not yet been implemented in the model. NERI’s Eulerian model DEOM, which was the version before DEHM-REGINA has taken part in an inter-comparison between four similar models in Europe. The model did not have the same resolution as several of the other models, men did generally well in the comparison.

 

NERI’s OML models represent state-of-the-art within Gaussian plume models. The model has been tested against other similar models within an international harmonisation society, where it has shown good results. A similar scientific review for odour modelling with the OML-odour model concluded that there is a need for improving the algorithms for building effects.  This work will naturally also be an advantage for the OML-dep version. OML-dep still misses an implementation of a detailed module for describing dry deposition to different surface types. Currently a module developed for the ACDEP-model has been implemented. Furthermore there is still strong need for measurement data for validation of the deposition in the nearby area of an NH3 source. This wil to some degree be solved with the ongoing eksperimental activities within the VMP-III research program.

Full report in pdf-format (555 kB).