Three‐dimensional solar radiation effects on the actinic flux field in a biomass‐burning plume

Abstract

Three‐dimensional (3‐D) solar radiative transfer models describe radiative transfer under inhomogeneous atmospheric conditions more accurately than the commonly used one‐dimensional (1‐D) radiative transfer models that assume horizontal homogeneity of the atmosphere. Here results of 3‐D radiative transfer simulations for a biomass‐burning plume are presented and compared with local one‐dimensional (l‐1‐D) simulations, i.e., 1‐D simulations in every column of the model domain. The spatial distribution of the aerosol particles was derived from a 3‐D atmospheric transport simulation. We studied the impact of 3‐D radiative effects on the actinic flux within the plume center. The differences in the actinic flux between results from the 3‐D and the l‐1‐D simulations are considerable, ranging from −40% to more than +200%, depending on the wavelength, solar zenith angle, and the absorbing properties of the aerosol. The reason for this discrepancy is the neglect of horizontal photon transport in the 1‐D simulation. These large 3‐D effects on the actinic flux have the potential to influence significantly the in‐plume photochemistry.