Spatial and Temporal Variability in OMI NO2 Observations and NOx Emissions Inventories in Eastern Texas

Elena McDonald-Buller, Gary McGaughey, Yosuke Kimura, Mike Feldman, and David T. Allen

Center for Energy and Environmental ResourcesThe University of Texas at Austin

Air Quality and Applied Sciences Team 6th Semi-Annual Meeting

January 15-17, 2014

Study Objectives

• Examine spatial and temporal trends in OMI tropospheric NO2 column densities over eastern Texas sub-regions during 2005-2010.

• Compare relative changes in OMI NO2 tropospheric column densities to those of ground-level NO2 concentrations across the Dallas/Fort Worth and Houston-Galveston-Brazoria/Beaumont-Port Arthur areas during 2005-2010.

• Compare observed NO2 trends between 2006-2010 to NOx emissions inventories for 2006 and 2012.

Datasets• Tropospheric NO2 Columns

– Retrieved from OMI– Version 2.0.1 of DOMINO product

http://www.temis.nl/index.php– 1300 to 1400 LST; 2005-2010– Criteria to retain data considered

spatial location, product flags for row anomaly and cloud interference, surface albedo

• Ground-level NO2 Concentrations– Hourly AQS measurements from

TCEQ:http://www.tceq.texas.gov/agency/data/aq-data.html

– Dallas and Houston at 1300 LST; 2005-2010

• Bottom-up NOx Inventories for June 2006 and 2012 – Developed by TCEQ in support of

Dallas/Fort Worth SIP

10 Geographic Sub-Regions in Eastern Texas

Annual Mean of Monthly Average OMITropospheric NO2 Column Densities

2006 (left) and 2010 (right)

Annual OMI Tropospheric NO2 Column Densities in Dallas and Houston: 2005-

2010

Box and whisker plot: horizontal bar represents the median, the box represents the 25th and 75th percentiles, and the whiskers represents the 5th and 95th percentiles.

Annual Mean

Annual OMI Tropospheric NO2 Column Densities in Austin/San Antonio, Tyler/Longview/Marshall/Corpus

Christi/Victoria : 2005-2010

Box and whisker plot: horizontal bar represents the median, the box represents the 25th and 75th percentiles, and the whiskers represents the 5th and 95th percentiles.

Annual Mean

Annual Mean OMI Tropospheric NO2 Column Densities and Surface NO2 Concentrations

in DFW (left) and HGB/BPA (right): 2005-2010

0.0

1.0

2.0

3.0

4.0

5.0

6.0

2005 2006 2007 2008 2009 2010Year

Satellite (*10^15 molecules/cm^2)

Monitored (ppb)

DFW

0.0

1.0

2.0

3.0

4.0

5.0

6.0

7.0

8.0

2005 2006 2007 2008 2009 2010Year

Satellite (*10^15 molecules/cm^2)

Monitored (ppb)

HGB/BPA

Reductions between 2005 and 2010:DFW: 27% (OMI); 33% (surface) HGB/BPA: 15% (OMI); 19% (surface)

Daily Average NOx Emissions (tons/km2/day) and Relative Changes Between 2006 and 2012 by

Eastern Texas Sub-Regions and Emissions Source Categories

Relative Changes in Annual Mean OMI Tropospheric NO2 Column Densities (2006-2010) and in Average Daily NOx Emissions (2006-2012) in Eastern Texas

Sub-Regions(For DFW and HGB/BPA, relative changes in annual mean NO2 at ground monitors (2006-2012) also shown)

Summary• Spatial and temporal trends in OMI tropospheric NO2 column densities

were investigated for eastern Texas:– Between 2005 and 2010, NO2 column densities declined over most

eastern Texas areas, with pronounced reductions in the Dallas and Houston areas.

– Annual average NO2 concentrations across ground monitoring sites in DFW and HGB-BPA also declined.

• Relative changes in NOx emissions from mobile sources and, in certain sub-regions, oil and gas production activities are projected to be substantial between 2006 and 2012.

• Comparisons between inventories and observations suggest the need for further investigations in sub-regions outside of DFW and HGB/BPA– What are the uncertainties in these inventories?– Surface monitoring networks are not as dense; utility in using

satellite observations to support analyses of air quality trends (e.g. top-down emissions estimates for informing emissions inventories)

– Inter-comparisons among satellite data products