Review and Improvement of Methods for Estimating Rates of Photolysis inPhotochemical Models (Volume 1)

摘要

Photolysis of species such as NO2 and formaldehyde influence significantly theformation of photochemical air pollution. Improved description of spatial and temporal variations in photolysis rates is needed, and improving the description of ultraviolet light intensity is key to improving urban and regional air quality models in this respect. Radiative transfer models were reviewed, and the Tropospheric Ultraviolet-Visible (TUV) model was implemented as a flexible photolysis module for online use within air quality models. Radiation measurements from the 1997 Southern California Ozone Study were used to assess the contributions of aerosols and ozone to variability in atmospheric optical depth. Aerosols were found to account for 90% or more of the observed variability in optical depth. Sensitivity analysis was combined with an assessment of the likely range of variation for key TUV inputs parameters to estimate their influence on photolysis rate uncertainty. The amount of aerosol and its relative efficiency in scattering versus absorbing UV radiation each were found to lead to -10% uncertainties in photolysis rate coefficients.