The vienna workshop on intercomparison of condensation nuclei and aerosol particle counters

Abstract

Atmospheric aerosols are considered an important factor influencing the evolution of the global climate. The present global database on atmospheric aerosol concentrations, however, appears to be still incomplete and partly inconsistent. Accordingly, the present measuring network needs to be improved and standardized. Various instruments are presently used for the measurement of aerosol particle concentrations in the atmosphere. However, direct comparison of data obtained from instruments with different measuring principles is generally complicated. For obtaining a consistent database on atmospheric aerosols, it is necessary to identify primary and transfer calibration standards for aerosol concentration measurement and to perform intercomparisons of various aerosol particle counters. It would be useful to develop a basic set of instrumentation. During an experimental workshop at the University of Vienna, various instruments for measurement of aerosol number concentration were compared using several well-defined aerosols in a linear flow system. Different expansion type, continuous flow type and mixing type condensation nuclei counters, an optical particle counter, different types of electrical aerosol spectrometers, and a Faraday cup electrometer were considered. In many cases satisfactory agreement of the instruments was found, however, for certain experimental conditions considerable deviations and nonlinearities have been observed. A detailed study of the detection efficiency has been performed for several instruments.