Evaluation of CMAQ predictions of the concentration and flux of nitrogen species over a loblolly pine forest
Abstract
Atmospheric deposition is an important input to water quality analyses such as Total Maximum Daily Loads (TMDLs) and to ecological assessments such as critical loads. Regional air quality models, such as the Community Multiscale air Quality (CMAQ) model, are important tools for providing these metrics. Evaluation of model predicted deposition values is important to establishing the uncertainty associated with the predictions. The Chemical Emission, Loss, Transformation and Interaction within Canopies (CELTIC) experiment, conducted at a loblolly pine forest in North Carolina, provides measurements of air concentration and flux of a suite of chemical species including NOy, PAN, MPAN, PPN, HNO3, NH3, particulate NO3-, and particulate NH4+. These species are important contributors to the nitrogen deposition budget, so evaluation of CMAQ concentration and deposition of these species is a critical need. For this study, we ran the CMAQ v5.0 unidirectional base model and using the bidirectional flux algorithm for NH3. Additionally, the model was run using a revised version of the chemical mechanism (CB05TUCL) which includes a better consideration of the multifunctional character of organic nitrates, including increases in aqueous solubility and gas-phase reaction rates. The revised chemical mechanism also includes recycling of organic nitrate and NOx in the gas-phase reactions of organic nitrates. Comparisons against field measurements are provided using the base model, the bidirectional flux model and the revised chemical mechanism. Results from this study provide important information on CMAQ model uncertainties and error in modeling nitrogen species.
- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2013
- Bibcode:
- 2013AGUFM.B43E0564S
- Keywords:
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- 0426 BIOGEOSCIENCES Biosphere/atmosphere interactions;
- 0315 ATMOSPHERIC COMPOSITION AND STRUCTURE Biosphere/atmosphere interactions;
- 0469 BIOGEOSCIENCES Nitrogen cycling