Numerical modeling of low level horizontal penetration seeding of supercooled cloud using liquid carbon dioxide (Fukuta 1996) has been carried out for the first time. The model is time-dependent, two-dimensional, covering a region 4 km × 6 km in the x and z directions with 50 m grid intervals. We assume a supercooled cumulus cloud has already been formed and the liquid water content as constant with height. The motion of ice crystal thermal in cloud is assumed like that of cumulus cell according to Scorer (1972). The ice crystals are assumed to be spherical shape and grow by consuming supercooled cloud entrained into the ice thermal. The model shows Roll up Expansion of the Twin Horizontal Ice crystal Thermal (RETHIT) due to buoyancy. Rise of horizontal ice crystal thermal while rotating, expanding and entraining the supercooled cloud volume leads to formation of ice crystals which possess sufficiently large size and necessary fall velocity in a large cloud volume within a likely cloud lifetime at the cloud top. Creation of large crystals with fast fall velocity assures subsequent changes for effective precipitation development. The centrifugal force is also found to act on ice particles and help them spread. Optimal seeding rate of liquid carbon dioxide is assessed as about 10 gram per second.
|ジャーナル||Journal of the Faculty of Agriculture, Kyushu University|
|出版ステータス||出版済み - 11 1 1998|
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