edu.ucar.opensky::articles:18001 UCAR/NCAR - Library OpenSky Support PO Box 3000 Boulder CO 80307-3000 opensky@ucar.edu http://opensky.ucar.edu/ homepage pointOfContact 2025-12-26T02:53:47.287348 ISO 19115-2 Geographic Information - Metadata - Part 2: Extensions for Imagery and Gridded Data ISO 19115-2:2009(E) https://n2t.org/ark:/85065/d7cz38q2 On the effectiveness of nitrogen oxide reductions as a control over ammonium nitrate aerosol 2016-03-02T00:00:00Z publication https://n2t.org/ark:/85065/d7cz38q2 https://doi.org/10.5194/acp-16-2575-2016 Pusede, S. author Duffey, K. author Shusterman, A. author Saleh, A. author Laughner, J. author Wooldridge, P. author Zhang, Q. author Parworth, C. author Kim, H. author Capps, S. author Valin, L. author Cappa, C. author Fried, A. author Walega, J. author Nowak, J. author Weinheimer, Andrew author Hoff, R. author Berkoff, T. author Beyersdorf, A. author Olson, J. author Crawford, J. author Cohen, R. author UCAR/NCAR - Library publisher Nitrogen oxides (NOx) have fallen steadily across the US over the last 15 years. At the same time, NOx concentrations decrease on weekends relative to weekdays, largely without co-occurring changes in other gas-phase emissions, due to patterns of diesel truck activities. These trends taken together provide two independent constraints on the role of NOx in the nonlinear chemistry of atmospheric oxidation. In this context, we interpret interannual trends in wintertime ammonium nitrate (NH₄NO₃) in the San Joaquin Valley of California, a location with the worst aerosol pollution in the US and where a large portion of aerosol mass is NH₄NO₃. Here, we show that NOx reductions have simultaneously decreased nighttime and increased daytime NH₄NO₃ production over the last decade. We find a substantial decrease in NH₄NO₃ since 2000 and conclude that this decrease is due to reduced nitrate radical-initiated production at night in residual layers that are decoupled from fresh emissions at the surface. Further reductions in NOx are imminent in California, and nationwide, and we make a quantitative prediction of the response of NH₄NO₃. We show that the combination of rapid chemical production and efficient NH₄NO₃ loss via deposition of gas-phase nitric acid implies that high aerosol days in cities in the San Joaquin Valley air basin are responsive to local changes in NOx within those individual cities. Our calculations indicate that large decreases in NOx in the future will not only lower wintertime NH₄NO₃ concentrations but also cause a transition in the dominant NH₄NO₃ source from nighttime to daytime chemistry. UCAR/NCAR - Library OpenSky Support PO Box 3000 Boulder CO 80307-3000 opensky@ucar.edu http://opensky.ucar.edu/ homepage pointOfContact PDF Text theme Resource Type 2016-01-01T00:00:00Z publication Copyright Author(s) 2016. This work is distributed under the Creative Commons Attribution 3.0 License. None eng geoscientificInformation