The Jungfraujoch: A Field Laboratory to Investigate the Free Troposphere A contribution to subproject AEROSOL

The free troposphere (FT) is a reservoir for primary and secondary pollutants which are transported there by dynamic mixing. Aerosol measurements in the FT are a convenient means for a quantification of the involved effects. Mountain stations are suitable for this purpose, since they allow the acquisition of long-term aerosol data, which are not available, for example, by measurements from aircraft platforms. Since July 1995, a number of aerosol parameters have been measured at the Jungfraujoch (JFJ) high-alpine research station (3454 m), Switzerland (Nyeki et al, 1998a). The seasonal cycle of aerosol concentration, measured since 1988 (Baltensperger et a/., 1997), exhibits a consistent maximum in summer and minimum in winter. This work presents measurements of the total and backwards hemispheric scattering coefficients (as?, CJBSP; TSI 3563 IN), the absorption coefficient ((TAP; Magee AE-10), the surface area concentration (S; PSI Instrument), the condensation nuclei concentration (CN; TSI CNC 3025, for particle diameters D > 3 nm; 3010 for D> 10 nm), the aerosol size distribution (16Scanning Mobility Particle Sizer (SMPS, TSI 3934), and the cloud liquid-water content (LWC; Gerber Scientific PVM-100), to define cloudless conditions.