Ž . Atmospheric Research 58 2001 295–313 www.elsevier.comrlocateratmos Impact of the Bergeron–Findeisen process on the release of aerosol particles during the evolution of cloud ice A. Schwarzenbock a, ) , S. Mertes a , J. Heintzenberg a , ¨ W. Wobrock b , P. Laj b a ( ) Institute for Tropospheric Research IfT , Permoserstr. 15, 04303 Leipzig, Germany b ( ) Laboratoire de Meteorologie Physique LaMP , UniÕersite Blaise Pascal – CNRS – OPGC, ´´ ´ 24 aÕenue des Landais, F-63177 Aubiere Cedex, France ` Received 23 September 2000; accepted 5 March 2001 Abstract Ž . The paper focuses on the redistribution of aerosol particles APs during the artificial nucleation and subsequent growth of ice crystals in a supercooled cloud. A significant number of Ž . the supercooled cloud droplets during icing periods seeding agents: C H , CO did not freeze as 3 8 2 was presumed prior to the experiment but instead evaporated. The net mass flux of water vapour Ž . from the evaporating droplets to the nucleating ice crystals Bergeron–Findeisen mechanism led to the release of residual particles that simultaneously appeared in the interstitial phase. The strong decrease of the droplet residuals confirms the nucleation of ice particles on seeding germs without natural aerosol particles serving as ice nuclei. As the number of residual particles during the seedings did not drop to zero, other processes such as heterogeneous ice nucleation, spontaneous freezing, entrainment of supercooled droplets and diffusion to the created particle-free ice germs must have contributed to the experimental findings. During the icing periods, residual mass concentrations in the condensed phase dropped by a factor of 1.1–6.7, as compared to the unperturbed supercooled cloud. As the Bergeron–Findeisen process also occurs without artificial seeding in the atmosphere, this study demonstrated that the hydrometeors in mixed-phase clouds might be much cleaner than anticipated for the simple freezing process of supercooled droplets in tropospheric mid latitude clouds. q 2001 Elsevier Science B.V. All rights reserved. Keywords: Mixed-phase cloud; Residual particles; Bergeron–Findeisen process; Mass concentration in condensed phases ) Corresponding author. Tel.: q 49-341-235-2151; fax: q 49-341-235-2361. Ž . E-mail address: alfons@tropos.de A. Schwarzenbock . ¨ 0169-8095r01r$ - see front matter q 2001 Elsevier Science B.V. All rights reserved. Ž . PII: S0169-8095 01 00096-5