Evaluation of simulated photochemical partitioning of oxidized nitrogen in the upper troposphere

Abstract

Abstract. Regional and global chemical transport models underpredict NO x (NO + NO 2 ) in the upper troposphere where it is a precursor to the greenhouse gas ozone. The NO x bias has been shown in model evaluations using aircraft data and total column NO 2 (molecules cm −2 ) from satellite observations (Napelenok et al., 2008). The causes of NO x underpredictions have yet to be fully understood due to the interconnected nature of simulated emission, transport, and chemistry processes. Recent observationbased studies, in the upper troposphere, identify chemical rate coefficients as a potential source of error (Olson et al., 2006;Ren et al., 2008). Since typical chemistry evaluation techniques are not available for upper tropospheric conditions, this study develops an evaluation platform from in situ observations, stochastic convection, and deterministic chemistry. We derive a stochastic convection model and optimize it using two simulated datasets of time since convection, one based on meteorology, and the other on chemistry. The chemistry surrogate for time since convection is calculated using seven different chemical mechanisms, all of which predict shorter time since convection than our meteorological analysis. We evaluate chemical simulations by inter-comparison and by pairing results with observations based on NO x :HNO 3 , a photochemical aging indicator. Inter-comparison reveals individual chemical mechanism biases and recommended updates. Evaluation against observations shows that all chemical mechanisms overpredict NO x Correspondence to: B. H. Henderson (barronh@gmail.com) removal relative to long-lived methanol and carbon monoxide. All chemical mechanisms underpredict observed NO x by at least 30%, and further evaluation is necessary to refine simulation sensitivities to initial conditions and chemical rate uncertainties.

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

“…The model framework used here was originally developed by Henderson et al (2011); the core framework and additions for this work are described below. The model framework relies on the convective turnover of the upper troposphere, or deep convection, that maintains a "persistent imbalance" (Prather and Jacob, 1997).…”

“…Photochemical processing includes gas-phase chemistry, partitioning to aerosols, and heterogeneous reactions. The gas-phase chemistry is simulated using the deterministic model used by GEOS-Chem "full" NO x -hydrocarbon simulations (Mao et al, 2009) with the improvements suggested by Henderson et al (2011). Additional reactions for CH 3 O 2 NO 2 have been added based on JPL11 with photolysis estimated using HNO 4 as a proxy (following Browne et al, 2011).…”

“…Although the exact value of τ is unknown, the range can be constrained by evaluation of chemical simulations and meteorological back trajectories. By evaluating the back trajectories from Fuelberg et al (2007), Henderson et al (2011) estimated a τ range from 40 to 58 h. By evaluating the chemical simulations, Henderson et al (2011) estimated a τ value for GEOS-Chem of 36 h. Because of the uncertainty in the τ value, the modeling framework will be evaluated at each average time-since-convection from 36 to 58 by one-hour intervals.…”

“…Olson et al (2006) and Ren et al (2008) both identify chemical reactions as a potential source of uncertainty. Henderson et al (2011) found that the chemistry representation of the global and regional models may cause a 30 % low-bias.…”

Decadal changes in summertime reactive oxidized nitrogen and surface ozone over the Southeast United States

“…Aircraft campaigns during the summers of 2004 and 2013, including the International Consortium for Atmospheric Research on Transport and Transformation (ICARTT; Singh et al, 2006), the Southeast Nexus (SENEX; Warneke et al, 2016), and the Studies of Emissions and Atmospheric Composition, Clouds and Climate Coupling by Regional Surveys (SEAC 4 RS; Toon et al, 2016), provide detailed characterization of tropospheric composition in this region separated by nearly a decade. These data have been widely used to evaluate model estimates of RON and ozone Pierce et al, 2007;Perring et al, 2009;Fischer et al, 2014;Hudman et al, 2007;Henderson et al, 2011;Hudman et al, 2009;Edwards et al, 2017;Baker and Woody, 2017;Travis et al, 2016;Mao et al, 2013b;Fisher et al, 2016;Yu et al, 2016;Liu et al, 2016). Together with measurements from surface networks, including the National Atmospheric Deposition Program (NADP) and EPA Air Quality System (AQS), these datasets enable a close examination of responses of RON and surface ozone to NO x emission reductions in this region.…”