El chichón – influence on aerosol optical depth and direct, diffuse and total solar irradiances at vancouver, b.c

Abstract

Solar radiation data for Vancouver, B.C. were used to determine the increase in aerosol optical depth and the changes in the total, direct, diffuse and net short‐wave radiation fluxes associated with the presence of aerosol that originated from the eruption of El Chichón (Mexico) in April 1982. The aerosol optical depth increased by 400% resulting in reductions of 33% in the direct and increases of 80% in the diffuse short‐wave radiation. These maximum changes were experienced some 9 months following the eruption. The relative insensitivity of the total short‐wave radiation (maximum reduction was 6%) suggests that the volcanic cloud was a strong forward scatterer rather than an absorber or back scatterer. Moreover, interannual variability in the surface albedo and a negative feedback associated with the dependence of the surface albedo on the directionality of the incident radiation resulted in no consistent change in the amount of short‐wave radiation absorbed by the Earth's surface. © Taylor & Francis Group, LLC.