Index Geophysics

Inferring ozone production in an urban atmosphere using measurements of peroxynitric acid

Observations of peroxynitric acid (HO₂NO₂) obtained simultaneously with those of NO and NO₂ provide a sensitive measure of the ozone photochemical production rate. We illustrate this technique for constraining the ozone production rate with observations obtained from the NCAR C-130 aircraft platform during the Megacity Initiative: Local and Global Research Observations (MILAGRO) intensive in Mexico during the spring of 2006. Sensitive and selective measurements of HO₂NO₂ were made in situ using chemical ionization mass spectrometry (CIMS). Observations were compared to modeled HO₂NO₂ concentrations obtained from the NASA Langley highly-constrained photochemical time-dependent box model. The median observed-to-calculated ratio of HO₂NO₂ is 1.18. At NO_x levels greater than 15 ppbv, the photochemical box model underpredicts observations with an observed-to-calculated ratio of HO₂NO₂ of 1.57. As a result, we find that at high NO_x, the ozone production rate calculated using measured HO₂NO₂ is faster than predicted using accepted photochemistry. Inclusion of an additional HO_x source from the reaction of excited state NO₂ with H₂O or reduction in the rate constant of the reaction of OH with NO₂ improves the agreement.

Spencer, K. M.

McCabe, D. C.

Crounse, J. D.

Olson, J. R.

Crawford, J. H.

Weinheimer, A. J.

Knapp, D. J.

Montzka, D. D.

Cantrell, C. A.

Hornbrook, R. S.

Mauldin III, R. L.

Wennberg, P. O.

2018-01-15

Text

application/pdf

10.5194/acp-9-3697-2009

https://acp.copernicus.org/articles/9/3697/2009/

eISSN: 1680-7324

eng