Changes in nitrogen oxides emissions in California during 2005–2010 indicated from top‐down and bottom‐up emission estimates

Min Huang; Kevin W Bowman; Gregory R Carmichael; Tianfeng Chai; R. Bradley Pierce; John R Worden; Ming Luo; Ilana B Pollack; Thomas B Ryerson; John B Nowak; J. Andrew Neuman; James M Roberts; Elliot L Atlas; Donald R Blake

doi:10.1002/2014JD022268

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Changes in nitrogen oxides emissions in California during 2005–2010 indicated from top‐down and bottom‐up emission estimates

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Changes in nitrogen oxides emissions in California during 2005–2010 indicated from top‐down and bottom‐up emission estimates

Min Huang, Kevin W Bowman, Gregory R Carmichael, Tianfeng Chai, R. Bradley Pierce, John R Worden, Ming Luo, Ilana B Pollack, Thomas B Ryerson, John B Nowak, …

Journal of geophysical research. Atmospheres, Vol.119(22), pp.12,928-12,952

11/27/2014

DOI: 10.1002/2014JD022268

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Abstract

In California, emission control strategies have been implemented to reduce air pollutants. Here we estimate the changes in nitrogen oxides (NOx = NO + NO2) emissions in 2005–2010 using a state‐of‐the‐art four‐dimensional variational approach. We separately and jointly assimilate surface NO2 concentrations and tropospheric NO2 columns observed by Ozone Monitoring Instrument (OMI) into the regional‐scale Sulfur Transport and dEposition Model (STEM) chemical transport model on a 12 × 12 km2 horizontal resolution grid in May 2010. The assimilation generates grid‐scale top‐down emission estimates, and the updated chemistry fields are evaluated with independent aircraft measurements during the NOAA California Nexus (CalNex) field experiment. The emission estimates constrained only by NO2 columns, only by surface NO2, and by both indicate statewide reductions of 26%, 29%, and 30% from ~0.3 Tg N/yr in the base year of 2005, respectively. The spatial distributions of the emission changes differ in these cases, which can be attributed to many factors including the differences in the observation sampling strategies and their uncertainties, as well as those in the sensitivities of column and surface NO2 with respect to NOx emissions. The updates in California's NOx emissions reduced the mean error in modeled surface ozone in the Western U.S., even though the uncertainties in some urban areas increased due to their NOx‐saturated chemical regime. The statewide reductions in NOx emissions indicated from our observationally constrained emission estimates are also reflected in several independently developed inventories: ~30% in the California Air Resources Board bottom‐up inventory, ~4% in the 2008 National Emission Inventory, and ~20% in the annual mean top‐down estimates by Lamsal et al. using the global Goddard Earth Observing System (GEOS)‐Chem model and OMI NO2 columns. Despite the grid‐scale differences among all top‐down and bottom‐up inventories, they all indicate stronger emission reductions in the urban regions. This study shows the potential of using space‐/ground‐based monitoring data and advanced data assimilation approach to timely and independently update NOx emission estimates on a monthly scale and at a fine grid resolution. The well‐evaluated results here suggest that these approaches can be applied more broadly. Key Points OMI and surface NO2 are assimilated separately/jointly using 4D‐Var methodOur top‐down estimates are consistent with the latest CARB bottom‐up inventoryUncertainties in modeled surface O3 in the Western U.S. are overall reduced

emission changes in California

top‐down and bottom‐up emissions

Western U.S. air quality

Details

Title: Subtitle: Changes in nitrogen oxides emissions in California during 2005–2010 indicated from top‐down and bottom‐up emission estimates
Creators: Min Huang - California Institute of Technology
Kevin W Bowman - California Institute of Technology
Gregory R Carmichael - University of Iowa
Tianfeng Chai - NOAA Air Resources Laboratory
R. Bradley Pierce - National Oceanic and Atmospheric Administration
John R Worden - California Institute of Technology
Ming Luo - California Institute of Technology
Ilana B Pollack - NOAA Earth System Research Laboratory
Thomas B Ryerson - NOAA Earth System Research Laboratory
John B Nowak - NOAA Earth System Research Laboratory
J. Andrew Neuman - NOAA Earth System Research Laboratory
James M Roberts - NOAA Earth System Research Laboratory
Elliot L Atlas - University of Miami
Donald R Blake - University of California, Irvine
Resource Type: Journal article
Publication Details: Journal of geophysical research. Atmospheres, Vol.119(22), pp.12,928-12,952
DOI: 10.1002/2014JD022268
ISSN: 2169-897X
eISSN: 2169-8996
Number of pages: 25
Grant note: NASA (NNX11AI52G)
Language: English
Date published: 11/27/2014
Academic Unit: Civil and Environmental Engineering; Nursing; Chemical and Biochemical Engineering
Record Identifier: 9984185464002771

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