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Impact of Updated Traffic Emissions on Hono Mixing Ratios Simulated for Urban Site in Houston, Texas : Volume 14, Issue 15 (20/08/2014)

By Czader, B. H.

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Book Id: WPLBN0003986084
Format Type: PDF Article :
File Size: Pages 26
Reproduction Date: 2015

Title: Impact of Updated Traffic Emissions on Hono Mixing Ratios Simulated for Urban Site in Houston, Texas : Volume 14, Issue 15 (20/08/2014)  
Author: Czader, B. H.
Volume: Vol. 14, Issue 15
Language: English
Subject: Science, Atmospheric, Chemistry
Collections: Periodicals: Journal and Magazine Collection (Contemporary), Copernicus GmbH
Publication Date:
Publisher: Copernicus Gmbh, Göttingen, Germany
Member Page: Copernicus Publications


APA MLA Chicago

Alvarez, S., Li, X., Choi, Y., Czader, B. H., & Lefer, B. (2014). Impact of Updated Traffic Emissions on Hono Mixing Ratios Simulated for Urban Site in Houston, Texas : Volume 14, Issue 15 (20/08/2014). Retrieved from

Description: Department of Earth and Atmospheric Sciences, University of Houston, Houston, USA. Recent measurements in Houston show that HONO traffic emissions are 1.7% of NOx emissions which is about twice the previously estimated value of 0.8% based on tunnel measurements in 2001. The 0.8% value is widely used to estimate mobile emissions of HONO for air quality modeling applications. This study applies the newly estimated HONO/NOx ratio in the WRF-SMOKE-CMAQ modeling system and estimates the impact of higher HONO traffic emissions on its mixing ratios. Since applied emission inventory resulted in overestimates of NOx mixing ratios and because HONO emissions and chemical formation depends on the magnitude of NOx, thus, before proceeding with HONO emission modifications emissions of NOx were adjusted to reflect current emission trends. The modeled mixing ratios of NOx were evaluated against measured data from a number of sites in the Houston area. Overall, the NOx mean value dropped from 11.11 ppbv in the base case to 7.59 ppbv in the NOx adjusted case becoming much closer to the observed mean of 7.76 ppbv. The Index of Agreement (IOA) is improved in the reduced NOx case (0.71 vs. 0.75) and the Absolute Mean Error (AME) is lowered from 6.76 to 4.94. The modeled mixing ratios of HONO were evaluated against the actual observed values attained at the Moody Tower in Houston. The model could not reproduce the morning HONO peaks when the low HONO/NOx ratio of 0.008 was used to estimate HONO emissions. Doubling HONO emissions from mobile sources resulted in higher mixing ratios, the mean value increased from 0.30 to 0.41 ppbv becoming closer to the observed mean concentrations of 0.69 but still low; AME was slightly reduced from 0.46 to 0.43. IOA for simulation that used the 2001 emission values is 0.63 while for simulation with higher HONO emission it increased to 0.70. Increased HONO emissions impacted OH mixing ratio, up to about 6% increase was found during morning and mid-day hours. The impact on ozone is marginal. This study results sheds light on the underestimated HONO and OH in the morning from global/regional chemical transport models with the typical emission of 0.8% HONO emission out of the total NOx emissions.

Impact of updated traffic emissions on HONO mixing ratios simulated for urban site in Houston, Texas

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