CIRRUS UNCINUS GENERATING CELLS AND THE EVOLUTION OF CIRRIFORM CLOUDS - 3. NUMERICAL COMPUTATIONS OF THE GROWTH OF THE ICE PHASE.

Equations were developed to calculate the growth of the ice phase in cirrus clouds. Calculations indicated that nucleation of ice crystals in cirrus uncinus heads forming at temperatures lower than minus 38 degree C generally should occur near the upwind base of the head, and in cirrostratus clouds at the top of the cloud. The growth of ice crystals and the resulting shape of cirrus uncinus clouds with an updraft velocity of 100 cm s** minus **1 were calculated. Latent heat release due to the ice crystal growth increased the initial updraft velocity only slightly. A downdraft velocity comparable in magnitude to the original updraft velocity was calculated to occur in the downshear part of the cirrus uncinus head.