Modification of a commercial condensation particle counter for boundary layer balloon-borne aerosol studies

J. Aerosol Sci. Vol. 29, Suppl. I, pp. S707-S708.1998 0 1998 Published by Elsevier Science Ltd. All rights reserved Printed in Great Britain 0021-8502&S $19.00+0.00

MODIFICATION OF A COMMERCIAL CONDENSATION PARTICLE COUNTER FOR BOUNDARY LAYER BALLOON-BORNE AEROSOL STUDIES J. Heintzenberg, A. Wiedensohler, T. Conrath, S. Ktitz and R. Dubois Institute for Tropospheric Research, Permoserstr. 15, D-04303 Leipzig, Germany KEYWORDS Balloon-CPC, number concentration, vertical profil MOTIVATION It is believed that atmospheric aerosol play a key role in global climate. Aerosol particles can effect the radiation balance of the earth directly and indirectly. The direct aerosol forcing of climate is due to the increased scattering and absorption of anthropogenic aerosol particles. The indirect effect of aerosol of climate is believed to be characterised by the modified of the number concentration and size of cloud droplets in polluted regions, and subsequently, by an increase of the cloud albedo. The quantify the aerosol effect in regional and global models, aerosol processes such as new particle formation, particle growth, and particle removal must be understood. Furthermore, physical and chemical aerosol parameters such as number, mass, size, and composition must be measured with a propitiate spatial and temporal resolution. To obtain vertical information about the particle number concentration and to study the process of new particle processes at ground based inversion layers, a balloon-borne condensation particle counter (CPC) was designed. DESIGN A commercial portable CPC for filter testing (TSI-8020) was modified and re-calibrated for boundary layer sounding of particle concentration >12 nm in diameter on a tethered balloon. A pre-impactor on the particle inlet sets an upper size limit of one micrometer to allow well defined interstitial aerosol measurements in cloudy air. The instruments works satisfactorily even during winter conditions up to 1000 m altitude. RESULTS Vertical profiles of the particle number concentration, temperature, humidity, wind speed and -direction have been measured using a tethered balloon as a platform for the instrumentation (Ktitz and Dubois, 1997). Daytime soundings up to 700 m above ground were done over Eastern Germany during a strong and persistent wintertime temperature inversion on January 18th 1996 (cf. Fig. 1). The inversion at 650 m above ground topped a closed stratus deck with a diffuse cloud base at 250 m. The profiles of temperature, humidity and particle number concentrations indicate that the layer below the inversion was well mixed. The evolution of the number concentration as a function of time and space with respect to the profiles of temperature, humidity and wind indicated new particle production at the top of the inversion layer. s707

Abstracts

S708

of the 5th International

Aerosol

Conference

1998

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Fig. 1: Vertical profiles of number concentrations 2 12 nm (NlZmn), temperature (T), and rel. humidity (rH) at the rural research station Melpitz, Germany during on 18th January, 1996 lo:30 CET SUMMARY

AND OUTLOOK

It was shown that the newly designed balloon-borne CPC is able to measure vertical profiles of meteorological parameters simultaneously with the particle number concentration >12 nm. In order to investigate further new particle production in the upper part of the boundary layer a second counting channel was added to the balloon payload allowing concurrent measurement of particle concentrations >5 nm and ~12 nm.