Evaluating Ammonia (NH₃) Predictions in the NOAA NAQFC for Eastern North Carolina Using Ground Level and Satellite Measurements

Abstract

Ammonia (NH3) in the atmosphere contributes to the formation of airborne fine particulate matter (PM2.5), which is associated with adverse human health effects. The emission, transport, reactions, and deposition of NH3 in the atmosphere are modeled using the Community Multiscale Air Quality (CMAQ) model, within the U.S. National Air Quality Forecast Capability (NAQFC). The purpose of this current work is to evaluate the capability of the NAQFC CMAQ model and to identify potential improvements to NH3 emissions estimates and prediction methods. This study focuses on CMAQ predictions of atmospheric NH3 in North Carolina, including a region with intensive animal production and enhanced NH3 emissions. The CMAQ model is run for July 2011 using a version of the 2011 National Emissions Inventory in which agricultural NH3 emissions were adjusted to reflect the lower end of the range of estimates from the current process‐based emissions model. The NAQFC CMAQ model overpredicted atmospheric NH3 at a continuous monitor in Clinton, NC, within the region of intensive animal production. The average concentration measured by the monitor was 6.6 ppbv, while the average predicted by the model was 10.5 ppbv, a 60% overprediction. Outside of the region of intensive animal production, both measured and modeled NH3 concentrations were low, 1.3 ppbv or less. The model underpredicted wet deposition of NH4+ and dry deposition of NH3. It is believed that the overestimation of NH3 at Clinton is attributable at least in part to the underestimation of wet and dry deposition in North Carolina.

An Ensemble-Variational Inversion System for the Estimation of Ammonia Emissions using CrIS Satellite Ammonia Retrievals

“…The normalized standard deviation of differences and correlation coefficients for the surface ammonia observations are shown in Saskatchewan), which is located in Clinton, North Carolina. Observations from this station, which were only available in July and August, showed an over-prediction of ammonia for both of these months when the original emissions were used, as was also found for this location by Battye et al (2019). Using the emissions from the inversions decreased the over-predictions at the Clinton station by 3.89 and 1.80 µg m −3 in July and August, respectively.…”

Comment on acp-2021-549

“…In this data set, only one station is located in one of the regions that showed a significant drop in emissions (Minnesota/Iowa, North Carolina, the Central Valley, southern Saskatchewan), which is located in Clinton, North Carolina. Observations from this station, which were only available in July and August, showed an over-prediction of ammonia for both of these months when the original emissions were used, as was also found for this location by Battye et al (2019). Using the emissions from the inversions decreased the over-predictions at the Clinton station by 3.89 and 1.80 µg m −3 in July and August, respectively.…”

Monthly Patterns of Ammonia Over the Contiguous United States at 2‐km Resolution

“…Large discrepancies exist between the chemical transport model predictions of NH 3 and observations on national and regional scales (Battye et al., 2019; Heald et al., 2012; Kelly et al., 2014, 2016, 2018; Nair et al., 2019; Zhu et al., 2013). Bottom‐up NH 3 emission inventories require detailed knowledge of spatially and temporally resolved farming practices that are rarely available (Paulot et al., 2014; Zhu et al., 2013).…”