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Published February 27, 2013 | Supplemental Material + Published
Journal Article Open

Inorganic and black carbon aerosols in the Los Angeles Basin during CalNex


We evaluate predictions from the Community Multiscale Air Quality (CMAQ version 4.7.1) model against a suite of airborne and ground-based meteorological measurements, gas- and aerosol-phase inorganic measurements, and black carbon (BC) measurements over Southern California during the CalNex field campaign in May/June 2010. Ground-based measurements are from the CalNex Pasadena ground site, and airborne measurements took place onboard the Center for Interdisciplinary Remotely-Piloted Aircraft Studies (CIRPAS) Navy Twin Otter and the NOAA WP-3D aircraft. BC predictions are in general agreement with observations at the Pasadena ground site and onboard the WP-3D, but are consistently overpredicted when compared to Twin Otter measurements. Adjustments to predicted inorganic mass concentrations, based on predicted aerosol size distributions and the AMS transmission efficiency, are shown to be significant. Owing to recent shipping emission reductions, the dominant source of sulfate in the L.A. Basin may now be long-range transport. Sensitivity studies suggest that severely underestimated ammonia emissions, and not the exclusion of crustal species (Ca^(2 +), K^+, and Mg^(2 +)), are the single largest contributor to measurement/model disagreement in the eastern part of the L.A. Basin. Despite overstated NO_x emissions, total nitrate concentrations are underpredicted, which suggests a missing source of HNO_3 and/or overprediction of deposition rates. Adding gas-phase NH_3 measurements and size-resolved measurements, up to 10 μm, of nitrate and various cations (e.g. Na^+, Ca^(2 +), K^+) to routine monitoring stations in the L.A. Basin would greatly facilitate interpreting day-to-day fluctuations in fine and coarse inorganic aerosol.

Additional Information

© 2012 American Geophysical Union. Received 22 May 2012; revised 4 December 2012; accepted 10 December 2012; Article first published online 19 February 2013. This work was funded by NOAA grant NA09OAR4310128 and by the State of California Air Resources Board (CARB) Agreement 10-328. NOAA's Climate and Air Quality programs supported the NOAA-P3 deployment. PLH and JLJ were supported by CARB-319 and DOE (BER, ASR program) DE-SC0006035, and PLH acknowledges a CIRES Visiting Postdoctoral Fellowship. This work was supported in part by the NOAA Health of the Atmosphere Program and the NOAA Climate Goal. We acknowledge four anonymous reviewers for their thorough and insightful comments. The authors would like to thank Nehzat Motallebi, Havala O. T. Pye, and Andreas Zuend for useful discussions, Ying Xie and Rob Pinder at the Environmental Protection Agency (EPA) for providing the SAPRC07TC chemical mechanism, Anne Perring, Joshua Schwartz, and David Fahey for the use of the SP2 measurements from the NOAA P3 aircraft and for useful discussion, John Holloway at NOAA for CO measurements from the NOAA P3 aircraft, Kemal Gurer for MM5 modeled data, and Jerome Fast for providing the Aerosol Modeling Testbed analysis toolkit. The statements and conclusions in this paper are those of the researchers (contractor) and not necessarily those of CARB. The mention of commercial products, their source, or their use in connection with material reported herein is not to be construed as actual or implied endorsement of such products.

Attached Files

Published - jgrd50108.pdf

Supplemental Material - 2012JD018136_SupplementalMaterial.pdf

Supplemental Material - 2012JD018136_readme.txt


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