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Published October 16, 2000 | Published
Journal Article Open

Quantitative constraints on the atmospheric chemistry of nitrogen oxides: An analysis along chemical coordinates


In situ observations Of NO_2, NO, NO_y, ClONO_2, OH, O_3, aerosol surface area, spectrally resolved solar radiation, pressure and temperature obtained from the ER-2 aircraft during the Photochemistry of Ozone Loss in the Arctic Region in Summer (POLARIS) experiments are used to examine the factors controlling the fast photochemistry connecting NO and NO_2 and the slower chemistry connecting NO_x and HNO_3. Our analysis uses "chemical coordinates" to examine gradients of the difference between a model and precisely calibrated measurements to provide a quantitative assessment of the accuracy of current photochemical models. The NO/NO_2 analysis suggests that reducing the activation energy for the NO+O_3 reaction by 1.7 kJ/mol will improve model representation of the temperature dependence of the NO/NO_2 ratio in the range 215–235 K. The NO_x/HNO_3 analysis shows that systematic errors in the relative rate coefficients used to describe NO_x loss by the reaction OH + NO_2 → HNO_3 and by the reaction set NO_2 + O_3 → NO_3; NO_2 + NO_3 → N_(2)O_5; N_(2)O_5 + H_(2)O → 2HNO_3 are in error by +8.4% (+30/−45%) (OH+NO_2 too fast) in models using the Jet Propulsion Laboratory 1997 recommendations [DeMore et al., 1997]. Models that use recommendations for OH+NO2 and OH+HNO_3 based on reanalysis of recent and past laboratory measurements are in error by 1.2% (+30/−45%) (OH+NO_2 too slow). The +30%/−45% error limit reflects systematic uncertainties, while the statistical uncertainty is 0.65%. This analysis also shows that the POLARIS observations only modestly constrain the relative rates of the major NO_x production reactions HNO3 + OH → H_(2)O + NO_3 and HNO_3 + hν → OH + NO_2. Even under the assumption that all other aspects of the model are perfect, the POLARIS observations only constrain the rate coefficient for OH+HNO_3 to a range of 65% around the currently recommended value.

Additional Information

© 2000 American Geophysical Union. Manuscript Accepted: 8 May 2000; Manuscript Received: 23 February 2000. Paper number 2000JD900290. The POLARIS experiments were supported by the NASA Upper Atmospheric Research Program and Atmospheric Effects of Aviation Project (M. Kurylo, P. DeCola, and R. Kawa, project managers). The ClO/ClONO_2/NO_2 instrument was developed with the support of the NASA Upper Atmospheric Research Program and the NASA Environmental Research Aircraft and Sensor Technology programs. Analyses presented in this paper were supported by NASA AEAP. K.K.P gratefully acknowledges an NSF graduate fellowship.We gratefully acknowledge the use of 0_3 measurements obtained by J. J. Margitan and M. H. Proffitt, Chuck Brock's contribution to the aerosol measurements and both experimental contributions to NO, NO_2, and NO_y measurements, and comments on this paper by David Fahey and Ru-Shan Gao.

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