Abstract
The Rocky Mountain Atmospheric Nitrogen and Sulfur (RoMANS II) study with field operations during November 2008 through November 2009 was designed to evaluate the composition and sources of reactive nitrogen in Rocky Mountain National Park, Colorado, USA. As part of RoMANS II, a mesoscale meteorological model was utilized to provide input for back trajectory and chemical transport models. Evaluation of the model's ability to capture important transport patterns in this region of complex terrain is discussed. Previous source-receptor studies of nitrogen in this region are also reviewed. Finally, results of several back trajectory analyses for RoMANS II are presented. The trajectory mass balance (TrMB) model, a receptor-based linear regression technique, was used to estimate mean source attributions of airborne ammonia concentrations during RoMANS II. Though ammonia concentrations are usually higher when there is transport from the east, the TrMB model estimates that, on average, areas to the west contribute a larger mean fraction of the ammonia. Possible reasons for this are discussed and include the greater frequency of westerly versus easterly winds, the possibility that ammonia is transported long distances as ammonium nitrate, and the difficulty of correctly modeling the transport winds in this area.
Highlights
Atmospheric deposition of reactive nitrogen in Rocky Mountain National Park, Colorado (RMNP), and surrounding areas of the Rocky Mountains has been the subject of research for 30 years (e.g., [1])
This paper describes the mesoscale meteorological modeling conducted for RoMANS II, including some evaluation of those results and gives details of a back-trajectorybased source apportionment of ammonia concentrations for RoMANS II
These results indicate that sources to both the east and west are important contributors to ammonia in RMNP
Summary
Atmospheric deposition of reactive nitrogen in Rocky Mountain National Park, Colorado (RMNP), and surrounding areas of the Rocky Mountains has been the subject of research for 30 years (e.g., [1]). During this time, scientists have endeavored to understand the levels and chemical composition of depositednitrogen [2, 3], the spatial and temporal trends [4, 5], the chemical and physical mechanisms by which nitrogen enters aquatic and ecological systems [6, 7], effects on biota [8, 9] and the dominant sources [10], emission rates [8, 11], and geographical and meteorological conditions (e.g., [11,12,13,14,15,16]) that cause deposition in sensitive alpine areas. The most densely populated region of Colorado, including the city of Denver (1610 meters MSL), is the Front Range urban corridor, which runs north-south through the center of the Advances in Meteorology (a)
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