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Fine-scale simulation of ammonium and nitrate over the South Coast Air Basin and San Joaquin Valley of California during CalNex-2010

Kelly, James T. and Baker, Kirk B. and Nowak, John B. and Murphy, Jennifer G. and Markovic, Milos Z. and VandenBoer, Trevor C. and Ellis, Raluca A. and Neuman, J. Andrew and Weber, Rodney J. and Roberts, James M. and Veres, Patrick R. and de Gouw, Joost A. and Beaver, Melinda R. and Newman, Sally and Misenis, Chris (2014) Fine-scale simulation of ammonium and nitrate over the South Coast Air Basin and San Joaquin Valley of California during CalNex-2010. Journal of Geophysical Research. Atmospheres, 119 (6). pp. 3600-3614. ISSN 2169-897X. doi:10.1002/2013JD021290.

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National ambient air quality standards (NAAQS) have been set for PM_2.5 due to its association with adverse health effects. PM_2.5 design values in the South Coast Air Basin (SoCAB) and San Joaquin Valley of California exceed NAAQS levels, and NH^(+)_(4) and NO^(-)_(3) make up the largest fraction of total PM2.5 mass on polluted days. Here we evaluate fine-scale simulations of PM_(2.5) NH^(+)_(4) and NO^(-)_(3) with the Community Multiscale Air Quality model using measurements from routine networks and the California Research at the Nexus of Air Quality and Climate Change 2010 campaign. The model correctly simulates broad spatial patterns of NH^(+)_(4) and NO^(-)_(3) including the elevated concentrations in eastern SoCAB. However, areas for model improvement have been identified. NH_3 emissions from livestock and dairy facilities appear to be too low, while those related to waste disposal in western SoCAB may be too high. Analyses using measurements from flights over SoCAB suggest that problems with NH3 predictions can influence NO^(-)_(3) predictions there. Offline ISORROPIA II calculations suggest that overpredictions of NH_x in Pasadena cause excessive partitioning of total nitrate to the particle phase overnight, while underpredictions of Na^+ cause too much partitioning to the gas phase during the day. Also, the model seems to underestimate mixing during the evening boundary layer transition leading to excessive nitrate formation on some nights. Overall, the analyses demonstrate fine-scale variations in model performance within and across the air basins. Improvements in inventories and spatial allocations of NH_3 emissions and in parameterizations of sea spray emissions, evening mixing processes, and heterogeneous ClNO_2 chemistry could improve model performance.

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de Gouw, Joost A.0000-0002-0385-1826
Newman, Sally0000-0003-0710-995X
Additional Information:© 2014 American Geophysical Union. Received 1 December 2013; Accepted 27 February 2014; Accepted article online 3 March 2014; Published online 28 March 2014. Discussions with Prakash Bhave, Rohit Mathur, and Jon Pleim of U.S. EPA (ORD) contributed to this work. The authors thank Allen H. Goldstein, Robert J. Weber, and Ronald C. Cohen of UC Berkeley for providing meteorology, O3, and organic nitrate data at Bakersfield. We also thank Barry Lefer of the University of Houston for providing ceilometer and NOx data at Pasadena and Paul O. Wennberg of Cal Tech for providing HNO3 data at Bakersfield. The authors also recognize the contributions of Chris Allen, Allan Beidler, James Beidler, Alison Eyth, Rich Mason, Norm Possiel, Alexis Zubrow, and Tyler Fox, and we thank the three anonymous reviewers for helpful suggestion.
Subject Keywords:CalNex; ammonia; sodium; aerosol thermodynamics; California; CMAQ
Issue or Number:6
Record Number:CaltechAUTHORS:20140617-094526903
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Official Citation:Kelly, J. T., et al. (2014), Fine-scale simulation of ammonium and nitrate over the South Coast Air Basin and San Joaquin Valley of California during CalNex-2010, J. Geophys. Res. Atmos., 119, 3600–3614, doi:10.1002/2013JD021290.
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:46301
Deposited By: Jason Perez
Deposited On:19 Jun 2014 22:17
Last Modified:10 Nov 2021 17:23

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