Air Quality Modeling of Ammonia: A Regional Modeling Perspective

The talk will address the status of modeling of ammonia from a regional modeling perspective, yet the observations and comments should have general applicability. The air quality modeling system components that are central to modeling ammonia will be noted and a perspective on their contribution to the overall uncertainty will be given. Special attention to the overall importance of ammonia emissions and their uncertainty will be given with illustrations from inverse modeling. The capability of our physical and chemical modeling of the ammonia part of the inorganic system will be put in perspective vis a vis the overall inorganic system uncertainties. Issues related to estimating the dry deposition of ammonia will be noted. The large uncertainty in interpretations of the ammonia budget will then be raised, including our poor understanding of the regional or continental budget. Perspectives on local versus long-range transport from regional analyses will be given, modeled budget analyses will be presented and some discrepancies with conventional wisdom noted. This leads into a further discussion of issues that can affect attribution and introduce biases. The talk concludes with a set of recommendation of research directions that will help improve the modeling of ammonia, support better evaluation of models and aid interpretation of the ammonia system.