Spectrophone measurements of the absorption of solar radiation by aerosol

Absorption of the direct solar beam was measured using an instrument based on the spectrophone. The method is described and results obtained from filtered and unfiltered air samples are presented. This enabled the aerosol's contribution to the absorption to be determined. Comparison of this absorption was made with the local visibility: with a visibility of 10km the heating rates observed were typically 0.2K day−1, increasing to 0.5K day−1 when smoke made a major contribution to the aerosol.