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The NO_x-HNO_3 System in the Lower Stratosphere: Insights from In Situ Measurements and Implications of the J_(HNO_3)-[OH] Relationship

Perkins, K. K. and Hanisco, T. F. and Cohen, R. C. and Koch, L. C. and Stimpfle, R. M. and Voss, P. B. and Bonne, G. P. and Lanzendorf, E. J. and Anderson, J. G. and Wennberg, P. O. and Gao, R. S. and Del Negro, L. A. and Salawitch, R. J. and McElroy, C. T. and Hintsa, E. J. and Loewenstein, M. and Bui, T. P. (2001) The NO_x-HNO_3 System in the Lower Stratosphere: Insights from In Situ Measurements and Implications of the J_(HNO_3)-[OH] Relationship. Journal of Physical Chemistry A, 105 (9). pp. 1521-1534. ISSN 1089-5639.

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During the 1997 Photochemistry of Ozone Loss in the Arctic Region in Summer (POLARIS) mission, simultaneous in situ observations of NO_x and HO_x radicals, their precursors, and the radiation field were obtained in the lower stratosphere. We use these observations to evaluate the primary mechanisms that control NO_x−HNO_3 exchange and to understand their control over the partitioning between NO_2 and HNO_3 in regions of continuous sunlight. We calculate NO_x production (P_(NO)_x) and loss (L_(NO)_x) in a manner directly constrained by the in situ measurements and current rate constant recommendations, using approaches for representing albedo, overhead O_3 and [OH] that reduce model uncertainty. We find a consistent discrepancy of 18% between modeled rates of NO_x production and loss (L_(NO)_x = 1.18P_(NO)_x) which is within the measurement uncertainty of ±27%. The partitioning between NO_x production processes is [HNO_3 + OH (41 ± 2)%; HNO+3 + hν (59 ± 2)%] and between NO_x loss processes is [NO_2 + OH, 90% to >97%; BrONO_2 + H_2O, 10% to <3%]. The steady-state description of NO_x−HNO_3 exchange reveals the significant influence of the tight correlation between the photolysis rate of HNO_3 and [OH] established by in situ measurements throughout the lower stratosphere. Parametrizing this relationship, we find (1) the steady-state value of [NO_2]_(24h-avg)/[HNO_3] in the continuously sunlit, lower stratosphere is a function only of temperature and number density, and (2) the partitioning of NO_x production between HNO_3 + OH and HNO_3 + hν is nearly constant throughout most of the lower stratosphere. We describe a methodology (functions of latitude, day, temperature, and pressure) for accurately predicting the steady-state value of [NO_2]_(24h-avg)/[HNO_3] and the partitioning of NO_x production within these regions. The results establish a metric to compare observations of [NO_2]_(24h-avg)/[HNO_3] within the continuously sunlit region and provide a simple diagnostic for evaluating the accuracy of models that attempt to describe the coupled NO_x−HO_x photochemistry in the lower stratosphere.

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Wennberg, P. O.0000-0002-6126-3854
Alternate Title:The NOx-HNO3 System in the Lower Stratosphere: Insights from In Situ Measurements and Implications of the J(HNO3)-[OH] Relationship
Additional Information:© 2001 American Chemical Society. Publication Date (Web): January 5, 2001. Received: July 14, 2000; In Final Form: November 2, 2000. We thank the NASA Upper Atmospheric Research Program and Atmospheric Effects of Aviation Project for supporting the POLARIS field campaign. The development of the new ClO/ClONO_2/NO_2 instrument was supported by the NASA Upper Atmospheric Research Program and Environmental Research Aircraft and Sensor Technology programs. K.K.P. gratefully acknowledges a graduate fellowship from NSF. We also thank P. A. Newman, L. R. Lait, and M. R. Schoberl for providing the back-trajectory calculations, C. R. Webster for providing N_2O^(ALIAS), J. C. Wilson for providing aerosol surface area density, and E. R. Nash for providing the climatological mean temperatures. Lastly, we thank N. M. Donahue for his useful input on this manuscript.
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NSF Graduate Research FellowshipUNSPECIFIED
Issue or Number:9
Record Number:CaltechAUTHORS:20140625-103136729
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Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:46500
Deposited By: Ruth Sustaita
Deposited On:25 Jun 2014 18:00
Last Modified:03 Oct 2019 06:44

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