An Efficient Method for Online Calculations of Photolysis and Heating Rates

Abstract

The authors present a computationally highly efficient method for the online calculation of photolysis and heating rates, which is especially suited for coupled transport?chemistry models. For this purpose, the spectral range 178.6 nm ≤ ? ≤ 752.5 nm, which is important for photochemistry in the troposphere and middle atmosphere, is divided into eight wavelength bands. For each band a parameterization of its contribution to photolysis and heating rates for a purely absorbing atmosphere is proposed, taking into consideration only absorption by O2 and O3. Scattering by molecules, aerosols, and clouds are taken into account by a correction factor, which is calculated online with a radiative transfer code at only one wavelength within each interval. The method yields photolysis and heating rates with less than 10% error for solar zenith angles less than 80° in the troposphere and even beyond in the stratosphere.