Measured aerosol light scattering coefficients compared with values calculated from EAA and optical particle counter measurements: improving the utility of the comparison

Abstract The aerosol light scattering coefficient measured with a nephelometer, b sp , was compared with β sp , the aerosol light scattering coefficient calculated from size distributions measured with an electrical aerosol analyzer (EAA) and optical particle counters (OPC). Laboratory measurements were made on aerosols of known refractive index. For DOP (dioctylphthalate) and NaCl aerosols, the ratio β sp b sp increased from an average of 0.58 to an average of 0.85 when the optical counter was calibrated for the refractive index of the aerosol and the EAA data were replaced by OPC data in the 0.316–0.562 μm range. These corrections increased the calculated scattering in that size range by factors ranging from two to four. In field studies, b sp is often compared with β sp to determine if a particular optical model is consistent with measured properties. Two examples show that accurately measured physical size distributions can help in testing models of the optical properties of the aerosol. However, errors of the magnitude seen in the 0.316–0.562 EAA range and caused by incorrect OPC calibrations reduce the value of the comparisons.