Atmospheric Chemistry and Physics Discussions www.atmos-chem-phys-discuss.net 1680-7367 1680-7375 3 4 2003 10.5194/acpd-3-3361-2003 http://www.atmos-chem-phys-discuss.net/3/3361/2003/ http://www.atmos-chem-phys-discuss.net/3/3361/2003/acpd-3-3361-2003.html http://www.atmos-chem-phys-discuss.net/3/3361/2003/acpd-3-3361-2003.pdf 3361 3372 2003-01-07 Comment on evidence for surface-initiated homogenous nucleation J. E. Kay V. Tsemekhman B. Larson M. Baker B. Swanson Department of Earth and Space Sciences, University of Washington, Seattle, USA Applied Physics Laboratory, University of Washington, Seattle, USA We investigate theoretical, laboratory, and atmospheric evidence for a recently proposed hypothesis: homogenous ice nucleation occurs at the surface, not in the volume, of supercooled water drops. Using existing thermodynamic arguments, laboratory experiments, and atmospheric data, we conclude that ice embryo formation at the surface cannot be confirmed or disregarded. Ice nucleation rates measured as a function of drop size in an air ambient could help distinguish between volume and surface nucleation rates.