%0 journal article
%@ 1867-1381
%A Hermann, M., Weigelt, A., Assmann, D., Pfeifer, S., Mueller, T., Conrath, T., Voigtlaender, J., Heintzenberg, J., Wiedensohler, A., Martinsson, B.G., Deshler, T., Brenninkmeijer, C.A.M., Zahn, A.

%D 2016
%J Atmospheric Measurement Techniques
%N 5
%P 2179-2194 
%R doi:10.5194/amt-9-2179-2016
%T An optical particle size spectrometer for aircraft-borne measurements in IAGOS-CARIBIC
%U https://doi.org/10.5194/amt-9-2179-2016
5 
%X The particle number size distribution is an important parameter to characterize the atmospheric aerosol and its influence on the Earth's climate. Here we describe a new optical particle size spectrometer (OPSS) for measurements of the accumulation mode particle number size distribution in the tropopause region on board a passenger aircraft (IAGOS-CARIBIC observatory: In-service Aircraft for a Global Observing System – Civil Aircraft for Regular Investigation of the Atmosphere Based on an Instrument Container). A modified KS93 particle sensor from RION Co., Ltd., together with a new airflow system and a dedicated data acquisition system, is the key component of the CARIBIC OPSS. The instrument records individual particle pulse signal curves in the particle size range 130–1110 nm diameter (for a particle refractive index of 1.47-i0.006) together with a time stamp and thus allows the post-flight choice of the time resolution and the size distribution bin width. The CARIBIC OPSS has a 50 % particle detection diameter of 152 nm and a maximum asymptotic counting efficiency of 98 %. The instrument's measurement performance shows no pressure dependency and no particle coincidence for free tropospheric conditions. The size response function of the CARIBIC OPSS was obtained by a polystyrene latex calibration in combination with model calculations. Particle number size distributions measured with the new OPSS in the lowermost stratosphere agreed within a factor of 2 in concentration with balloon-borne measurements over western North America. Since June 2010 the CARIBIC OPSS is deployed once per month in the IAGOS-CARIBIC observatory.