Condensation Nuclei (CN) and Ultrafine CN in the Free Troposphere to 12 km:: A case study over the Jungfraujoch high-alpine research station

Condensation nuclei (CN) were measured in the free troposphere (FT) above the Jungfraujoch (JFJ) high-alpine research station (3454 m; Switzerland) from 4.5 to 12 km asl in a case study on July 30, 1997. Vertical profiles of CN concentration for d greater than or equal to 5 nm (N-greater than or equal to 5), d greater than or equal to 15 nm (N-greater than or equal to 15) were measured, and indicated that ultrafine CN (UCN; 5 less than or equal to: d less than or equal to 15 nm; N5-15) exhibited a distinct increase with altitude. Some evidence for near-constant values of d(logCN)/dz within discrete layers was found, which generally coincided with different airmasses as delineated by changes in the lapse rate d theta/dz at similar to 5.5, 6.4, 9.0 and 10.6 km asl. In addition, CN concentration was mapped over a 40 x 75 km horizontal domain at 8.0 km asi centered above the JFJ. A pronounced variation in N-greater than or equal to 5, N-greater than or equal to 15 and specific humidity, but not in UCN, exhibited quasi-stationary 2-D features and was attributed to the chance encounter of a mountain wave. The case study provides further evidence that the upper FT may be a source of new particles.