Portable cell for simultaneously measuring the coefficients of light scattering and extinction for ambient aerosols

A portable multipass cell is described in which optical transmittance and scattering measurements are made simultaneously on the same volume of aerosol. The cell is filled with ambient aerosol in which the dispersed phase has been concentrated centrifugally by more than 1 order of magnitude. The cell was tested on board a ship for a wide variety of sea and atmospheric conditions. Measurement errors were identified and evaluated. The mean resolution of the transmittances was plus or minus 0.16% and the mean resolution of the scattering coefficients was plus or minus 0.000005 per m. Their combination gives the bulk single scattering albedo, which was resolved by plus or minus 0.1 for atmospheres with a visual range of approximately 50 km and by rapidly increasing accuracy for shorter ranges. Concentrating the dispersed phase was not essential for the scattering measurements and, with achievable improvements in the cell, would not be necessary for the transmittance measurements.