1Cooperative Institute for Research in Environmental Sciences, University of Colorado, Boulder, CO 80309, USA
2NOAA Earth System Research Laboratory, Boulder, CO 80305, USA
3Institute of Environmental Physics, University of Bremen, Germany
4Rosenstiel School of Marine and Atmospheric Science, Division of Atmospheric and Marine Chemistry, University of Miami, Miami, FL 33149, USA
5Royal Netherlands Meteorological Institute (KNMI), De Bilt, The Netherlands
6Eindhoven University of Technology, Eindhoven, The Netherlands
7Center for Ecology and Hydrology, Maclean Building, Benson Lane, Crowmarsh Gifford, 16 Wallingford, Oxfordshire, OX10 8BB, UK
8NCAR, Earth Observing Laboratory, Boulder, CO 80307, USA
9NASA Goddard Space Flight Center, Laboratory for Atmosphere, Greenbelt, MD 20771, USA
10Earth and Space Science, Chalmers University of Technology, Gothenburg, Sweden
11Sensor Sense, Nijmegen, The Netherlands
*now at: Centro de Ciencias de la Atmósfera, Universidad Nacional Autónoma de Mexico, Mexico
Received: 20 Jul 2011 – Discussion started: 27 Jul 2011
Abstract. Satellite and aircraft observations made during the 2006 Texas Air Quality Study (TexAQS) detected strong urban, industrial and power plant plumes in Texas. We simulated these plumes using the Weather Research and Forecasting-Chemistry (WRF-Chem) model with input from the US EPA's 2005 National Emission Inventory (NEI-2005), in order to evaluate emissions of nitrogen oxides (NOx = NO + NO2) and volatile organic compounds (VOCs) in the cities of Houston and Dallas-Fort Worth. We compared the model results with satellite retrievals of tropospheric nitrogen dioxide (NO2) columns and airborne in-situ observations of several trace gases including NOx and a number of VOCs. The model and satellite NO2 columns agree well for regions with large power plants and for urban areas that are dominated by mobile sources, such as Dallas. However, in Houston, where significant mobile, industrial, and in-port marine vessel sources contribute to NOx emissions, the model NO2 columns are approximately 50%–70% higher than the satellite columns. Similar conclusions are drawn from comparisons of the model results with the TexAQS 2006 aircraft observations in Dallas and Houston. For Dallas plumes, the model-simulated NO2 showed good agreement with the aircraft observations. In contrast, the model-simulated NO2 is ~60% higher than the aircraft observations in the Houston plumes. Further analysis indicates that the NEI-2005 NOx emissions over the Houston Ship Channel area are overestimated while the urban Houston NOx emissions are reasonably represented. The comparisons of model and aircraft observations confirm that highly reactive VOC emissions originating from industrial sources in Houston are underestimated in NEI-2005. The update of VOC emissions based on Solar Occultation Flux measurements during the field campaign leads to improved model simulations of ethylene, propylene, and formaldehyde. Reducing NOx emissions in the Houston Ship Channel and increasing highly reactive VOC emissions from the point sources in Houston improve the model's capability of simulating ozone (O3) plumes observed by the NOAA WP-3D aircraft, although the deficiencies in the model O3 simulations indicate that many challenges remain for a full understanding of the O3 formation mechanisms in Houston.
Revised: 25 Oct 2011 – Accepted: 27 Oct 2011 – Published: 16 Nov 2011
Kim, S.-W., McKeen, S. A., Frost, G. J., Lee, S.-H., Trainer, M., Richter, A., Angevine, W. M., Atlas, E., Bianco, L., Boersma, K. F., Brioude, J., Burrows, J. P., de Gouw, J., Fried, A., Gleason, J., Hilboll, A., Mellqvist, J., Peischl, J., Richter, D., Rivera, C., Ryerson, T., te Lintel Hekkert, S., Walega, J., Warneke, C., Weibring, P., and Williams, E.: Evaluations of NOx and highly reactive VOC emission inventories in Texas and their implications for ozone plume simulations during the Texas Air Quality Study 2006, Atmos. Chem. Phys., 11, 11361-11386, doi:10.5194/acp-11-11361-2011, 2011.