| 1. |
- Kim, S. W., et al.
(författare)
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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
- 2011
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Ingår i: Atmospheric Chemistry and Physics. - : Copernicus GmbH. - 1680-7316 .- 1680-7324. ; 11:22, s. 11361-11386
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Tidskriftsartikel (refereegranskat)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-FortWorth. 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. How-ever, in Houston, where significant mobile, industrial, and inport 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 similar to 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 (O-3) plumes observed by the NOAA WP-3D aircraft, although the deficiencies in the model O-3 simulations indicate that many challenges remain for a full understanding of the O-3 formation mechanisms in Houston.
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| 2. |
- Lewander, Magnus, et al.
(författare)
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Fast and sensitive time-multiplexed gas sensing of multiple lines using a miniature telecom diode laser between 1529 nm and 1565 nm
- 2011
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Ingår i: Applied Physics B. - : Springer Science and Business Media LLC. - 0946-2171 .- 1432-0649. ; 104:3, s. 715-723
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Tidskriftsartikel (refereegranskat)abstract
- High-sensitive multi-species detection around 1550 nm using a modulated grating Y-branch, MG-Y, diode laser tunable between 1529 nm and 1565 nm is presented. The MG-Y diode laser is based on the Vernier effect of two modulated gratings, and exhibits quasi-continuous tuning over 36 nm. Multi-species detection is achieved by fast sequential scanning of single absorption lines of CH4, CO, C2H2, and CO2 distributed over the tuning range of the diode laser. The laser wavelength is scanned about 10 GHz around each absorption line for 5 ms and this is followed by a discrete large jump in operating wavelength to the next line. The MG-Y diode laser has a good repeatability in output frequency between sequential scan segments (< 10 MHz) enabling averaging of the scans. The setup employs digital wavelength modulation spectroscopy, dWMS, with Fourier-based WMS retrieval, applicable through the use of data acquisition cards and coherent sampling. Absorbance sensitivity using 2f-WMS signals of 7x10(-7) in 30 s (all precisions in this paper are at the 1 sigma level) is demonstrated for sensing of four gases and 2x10(-7) when only one gas is detected. Corresponding numbers for 0.5 s of averaging are 4x10(-6) and 1x10(-6).
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