Angular truncation error in the integrating nephelometer
The atmospheric light scattering extinction coefficient measured with an integrating nephelometer has a systematic error resulting from light lost at the angular extremes of the physical integration of scattered light. This error was calculated for typical atmospheric aerosols for the Ahlquist and Charlson instrument (integration range is 8° to 170°). The range of error resulting from angular truncation was from 0 to 22 per cent and depended primarily on the exponent of the Junge panicle size distribution and the large particle size cut-off. The error was essentially independent of the particle refractive index, small particle cut-off below 0.1 ?m and the wavelength of light (436–600 nm). The calculated typical error of about 10 per cent agreed with previously published empirical and calculated results.