Scaling ozone photochemistry I

Introduction Conclusions References Tables Figures Back Close Abstract Introduction Conclusions References Tables Figures Back Close Full Screen / Esc Print Version Interactive Discussion EGU Abstract A scaling analysis has been used to capture the integrated behaviour of several pho-tochemical mechanisms for a wide range of precursor concentrations and a variety of environmental conditions. The Buckingham Pi method of dimensional analysis was used to express the relevant variables in terms of dimensionless groups. These group-5 ing show maximum ozone, initial NO x and initial VOC concentrations are made non-dimensional by the average NO 2 photolysis rate (j av) and the rate constant for the NO-O 3 titration reaction (k NO); temperature by the NO-O 3 activation energy (E NO) and Boltzmann constant (k) and total irradiation time by the cumulative j av ∆t photolysis rate (π 3). The analysis shows dimensionless maximum ozone concentration can be 10 described by a product of powers of dimensionless initial NO x concentration, dimen-sionless temperature, and a similarity curve directly dependent on the ratio of initial VOC to NO x concentration and implicitly dependent on the cumulative NO 2 photolysis rate. When Weibull transformed, the similarity relationship shows a scaling break with dimensionless model output clustering onto two straight line segments, parameterized 15 using four variables: two describing the slopes of the line segments and two giving the location of their intersection. A fifth parameter is used to normalize the model output. The scaling analysis, similarity curve and parameterization appear to be independent of the details of the chemical mechanism, hold for a variety of VOC species and mixtures and a wide range of temperatures and actinic fluxes.