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We present an analysis of correlations between O 3 , NO x reaction products (NO z ), and peroxides in photochemical models for polluted environments in comparison with measurements in the vicinity of Nashville, Tennessee. This analysis is associated with the use of O 3 /NO z , H 2 O 2 /NO z , and similar ratios as indicators for the relative impact of NO x and hydrocarbons (volatile organic compounds, VOC) on ozone formation. The measurements are used both to evaluate the NO x ‐VOC indicator theory and to identify NO x ‐VOC chemistry in Nashville. Results show that a linear correlation exists between O 3 and the sum 2H 2 O 2 + NO z , consistent between models and measurements. The ratio O 3 /2H 2 O 2 + NO z has a near‐constant value in both the Nashville urban plume and surrounding rural area. A similar correlation is found with total peroxides (O 3 versus 2peroxides + NO z ) but with greater scatter. The correlations between O 3 , NO z , and peroxides are consistent with an assumed dry deposition rate of 5 cm s −1 for H 2 O 2 and HNO 3 . Changes in dry deposition and RO 2 reaction rates cause minor adjustments in the NO x ‐VOC‐indicator analysis for H 2 O 2 /NO z . Measured indicator ratios for Nashville are close to the NO x ‐VOC transition predicted by models and form an intermediate point between previous measurements for Atlanta (NO x sensitive) and Los Angeles (VOC sensitive). The model ozone production efficiency (P(O 3 )/L(NO x )) is 3–4, significantly lower than would be derived from the O 3 ‐NO z slope (5–8).
Sillman et al. (Tue,) studied this question.