MEASUREMENTS OF ICE-FORMING RATES PRODUCED BY SUPERSONIC FLOW AND INVESTIGATION OF MECHANISMS OF ICE CRYSTAL GENERATION^*

The ice forming rates pi produced by supersonic flow have been measured in supercooled fog suspended in a cold chamber at temperatures of 0 to -12℃.It has been shown that the ice-forming rates are 1011 to 1012 crystals per gram of air at Mach numbers of 1.1 to 1.84 and total pressures below 6 atm,and that the ice-forming rates slowly increase with increasing Mach numbers and total pressures and with decreasing ambient temperatures.These results are theoretically consistent with the rules for expansion in supersonic flow.In review of mechanisms of ice crystal generation,authors propose that the homogeneous nucleation-free zing(condensation-freezing)of water vapor in supersonic flow be the dominant mechanism.In our opinion,supersonic flow,for artificial precipitation,could be expected to provide an economical,non-polluting and convenient technology,and suitable for the long-distance operation.The data obtained from our experiments indicate that it is feasible to develop a new technique for weather modification.