A modeling study of the stratospheric NO_x/NO_y and NO_x/HNO₃ ratios: Single‐ versus dual‐channeled mode of OH, NO₂ association

Abstract

[1] UARS observations bearing upon the NO x /NO y and NO x /HNO 3 ratios were revisited within the framework of advances in laboratory studies that were spurred by the findings, around 1999, of considerable model underestimation of the observations. The objective was to study the two models of the OH, NO 2 association reaction, one that considers the single HNO 3 product channel and the other that considers dual HNO 3 and HOONO products channels. Rate coefficients of the OH + HNO 3 and the single-channeled OH + NO 2 ! HNO 3 reactions recommended in JPL00-3 produce remarkably improved agreement between the modeled and observed NO x /HNO 3 and NO x /NO y , compared to the case with the recommendations in JPL-97. This agrees with the results of other previous studies, such as those using the Photochemistry of Ozone Loss in the Arctic Region in Summer and MkIV data. The consumption of OH, NO 2 pair in the lower stratosphere via the three-body association occurs at almost the same rate (within ±5%) whether the singleor the double-channeled version of that process is used with rate coefficients from JPL00-3. However, only 70-80% of this consumption yields HNO 3 in the dual-channeled version, compared to 100% in the case of the single-channeled version. Consequently, the dualchanneled model of HNO 3 formation performs better than the single-channeled model in predicting NO x /HNO 3 and NO x /NO y ratios. At 46.4 mbar, for example, the mean percentage difference between the modeled and the observed NO x /HNO 3 equals about À10%, if HOONO is included. The corresponding number is about À19% when HOONO is excluded. Because laboratory experiments on OH, NO 2 association that directly detect HOONO isomer are still maturing, further studies are needed. Further studies are also needed to understand the intriguing tendency of the model-measurement differences to maximize around 20 mbar.INDEX TERMS: 0317 Atmospheric Composition and Structure: Chemical kinetic and photochemical properties; 0322 Atmospheric Composition and Structure: Constituent sources and sinks; 0340 Atmospheric Composition and Structure: Middle atmosphere-composition and chemistry; KEYWORDS: OH, NO 2 association reaction, NO x /NO y ratio, HOONO channel, HOONO conformers, HNO 3 formation mechanism, NO x /HNO 3 ratio Citation: Prasad, S. S., A modeling study of the stratospheric NO x /NO y and NO x /HNO 3 ratios: Single-versus dual-channeled mode of OH, NO 2 association,

Impact of a moderate volcanic eruption on chemistry in the lower stratosphere: balloon-borne observations and model calculations

“…In particular for nitrogen gas-phase chemistry, revised kinetic data were recommended because, following a number of studies (e.g. Brown et al, 1999;Gao et al, 1999;Jucks et al, 1999;Osterman et al, 1999;Kondo et al, 2000;Prasad, 2003), a lower rate for the reaction of NO 2 with OH and a higher rate for HNO 3 with OH significantly reduced model-measurement discrepancies highlighted in former published work (e.g. Fahey et al, 1993;Kondo et al, 1997;Sen et al, 1998).…”

Impact of a moderate volcanic eruption on chemistry in the lower stratosphere: balloon-borne observations and model calculations

“…As a result, the amount of ozone-depleting NO x is strongly reduced (e.g. Prather, 1992;Johnston et al, 1992;Fahey et al, 1993;Mills et al, 1993;Solomon et al, 1994;Kondo et al, 1997;Sen et al, 1998;Dhomse et al, 2015), whereas HNO 3 amounts increase (Koike et al, 1993(Koike et al, , 1994Webster et al, 1994;Rinsland et al, 2003) as shown for the Pinatubo aerosols. Different chemical impacts on stratospheric ozone are expected depending on the altitude.…”

“…It results in the additional formation of HNO 3 on sulfate aerosols and in the formation of reactive chlorine in sunlight, where HOCl is rapidly photolysed releasing Cl radicals (e.g. Hofmann and Solomon, 1989;Prather, 1992;McElroy et al, 1992). This heterogeneous reaction is highly dependent on the water content in the aerosols and has been shown to be of considerable importance in determining the abundance of active chlorine available to destroy ozone under some conditions, i.e.…”

Photochemical production of odd nitrogen directly from O2, N2 principals: Atmospheric implications and related open issues

“…The present study followed the recommendations of JPL 00‐3 for the calculation of H 2 SO 4 wt% from temperature and the partial pressure of H 2 O, parameters for H 2 SO 4 solution and the uptake model parameters for ClONO 2 + H 2 O, ClONO 2 + HCl, HOCl + HCl reactions. This approach is the same as the approach taken by one of us [ Prasad , 2003a] in his study of the stratospheric NO X /NO Y and NO X /HNO 3 ratios. A useful comparison of the pre‐ and post‐ JPL00‐3 implementation of the reactions on sulfate aerosols can be found in that paper.…”

“…According to the current understanding of the stratospheric NO X /NO Y chemistry, the theoretical models underestimate that ratio [ Danilin et al , 1999]. Although the newer experimental data and theoretical models of OH, NO 2 association and the HNO 3 + OH reaction [e.g., Donahue et al , 1997; Brown et al , 1999a, 1999b; Golden and Smith , 2000] produce a significant improvement, the problem persists [ Prasad , 2003a]. As pointed out earlier, the may not provide any reprieve in this matter, since the new source affect both NO X and NO Y similarly.…”