Combining Bayesian methods and aircraft observations to constrain the HO<sup>.</sup> + NO<sub>2</sub> reaction rate

Abstract

Abstract. Tropospheric ozone is the third strongest greenhouse gas, and has the highest uncertainty in radiative forcing of the top five greenhouse gases. Throughout the troposphere, ozone is produced by radical oxidation of nitrogen oxides (NO x = NO + NO 2 ). In the upper troposphere (8-10 km), current chemical transport models under-estimate nitrogen dioxide (NO 2 ) observations. Improvements to simulated NO x production from lightning have increased NO 2 predictions, but the predictions in the upper troposphere remain biased low. The upper troposphere has low temperatures (T < 250 K) that increase the uncertainty of many important chemical reaction rates. This study constrains uncertain reaction rates by combining model predictions with measurements from the Intercontinental Chemical Transport Experiment-North America observational campaign. The results show that the nitric acid formation rate, which is the dominant sink of NO 2 and radicals, is currently overestimated by 22 % in the upper troposphere. The results from this study suggest that the temperature sensitivity of nitric acid formation is lower than currently recommended. Since the formation of nitric acid removes nitrogen dioxide and radicals that drive the production of ozone, the revised reaction rate will affect ozone concentrations in upper troposphere impacting climate and air quality in the lower troposphere.

Constraints on ship NO&lt;sub&gt;x&lt;/sub&gt; emissions in Europe using GEOS-Chem and OMI satellite NO&lt;sub&gt;2&lt;/sub&gt; observations

“…In particular, the value for the uptake coefficient γ N 2 O 5 in GEOS-Chem is high compared to recent laboratory and field estimates of this value (e.g. Brown et al, 2009;Mollner et al, 2010;Henderson et al, 2012;Butkovskaya et al, 2007Butkovskaya et al, , 2009. We conclude that the nested GEOS-Chem CTM is in close agreement with OMIobserved NO 2 columns over Europe.…”

Nitrogen Oxides Emissions, Chemistry, Deposition, and Export Over the Northeast United States During the WINTER Aircraft Campaign

“…GEOS‐Chem uses the rate constant recommended by the NASA Jet Propulsion Laboratory panel evaluation (Sander et al, ). Several studies have suggested that this rate constant might be 15–20% lower than the value recommended by Jet Propulsion Laboratory (Henderson et al, ; Mollner et al, ). As no measurements of OH, HO 2 , or H 2 O 2 were made as part of WINTER, we cannot directly evaluate our modeled OH concentrationss.…”

Emissions of nonmethane volatile organic compounds from open crop residue burning in the Yangtze River Delta region, China

“…The NO x /NO y ratio described in this work was corrected for this contribution. For the calculation, we conservatively assumed the average OH concentration of 2.0 × 10 6 molecules cm −3 and the rate constant for the reaction of NO 2 + OH → HNO 3 to be k = 2.58 × 10 −11 [ Henderson et al ., ], used in recent estimates of NO x lifetime in continental regions [ Browne and Cohen , ].…”