The production of high ice‐crystal concentrations in stratiform clouds

Abstract

AbstractThe appearance of ice crystals in high concentrations, of ∼ 500 1−1 in the −3 to −8°C zone of stratiform clouds, recently reported by Bower et al., is explained by the shedding of splinters by riming ice crystals at rates observed in the laboratory earlier by Hallett and Mossop. The appearance of a second maximum at −15°C, with small crystals of diameter less than 125 μm in concentrations of ∼ 1000 1−1, is attributed to the transport of small ice splinters produced in the Hallet‐Mossop zone that grow at small ice supersaturations in weak updraughts between the −8°C and −12°C levels, and thereafter at water saturation in convective cells containing liquid water and updraughts of 1 m s−1 between the −12°C and −15°C levels.