Collection kernels for the capture of Slver Iodide nuclei by cloud water droplets


  • L. Mathews
  • P. St.-Amand


Cloud and Precipitation Microphysics


Capture of Agl nuclei by cloud drops, through the microphysical  processes of inertial and interceptive impaction, Brownian  diffusion, and wake capture is expressed in terms of a collection  kernel as a function of Agl nuclei and cloud drop radii. Also, the  effect of phoretic forces and turbulence on the collection kernel  is assessed. For the capture of 0.01 to I0 um radius Agl by cloud droplets with radii 50 um or greater, the collection kernels are  greater than 10^-6. These kernels are large enough to bring  practical concentrations of Agl nuclei into contact with cloud  drops at a rate such asto cause rapid freezing of cloud water  accompanied by a large heat release if the updraft portion of a  cloud is seeded. However, impractically large amounts of nuclei  may be required to contact droplets in the downdraft portion of  a cloud, and more so, if drop evaporation is rapid and the drops  are positively charged.




Technical Notes and Correspondence