バルク法では、凝結水を落下が無視できる雲粒と落下する雨粒に分けて考えるが、雨粒と関係なく雲粒から雨粒へ変換する過程を autoconversion とよび、
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The initial stage of the collision-coalescence process whereby cloud droplets collide and coalesce to form drizzle drops.
Originally a term for the rate equation to approximate the transfer of cloud drops to drizzle. Because of the low collection efficiencies among cloud drops, autoconversion can be the limiting factor in the formation of drizzle
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