Observation of High Ice Particle Concentrations In Convective Cells and Cloud Glaciation Evolution

✍ Scribed by J.-F. Gayet; R. G. Soulage

• Publisher: John Wiley and Sons
• Year: 1992
• Tongue: English
• Weight: 840 KB
• Volume: 118
• Category: Article
• ISSN: 0035-9009
• DOI: 10.1002/qj.49711850402

✦ Synopsis

Abstract

During an investigation into convective cloud at a single temperature level near −6°C, observations by aircraft have found ice crystal concentrations significantly in excess (up to 600 L^−1^) of those to be expected from primary ice formation (i.e. ice multiplication). Despite the fact that the main conditions for the operation of the Hallet‐Mossop secondary ice multiplication process were fulfilled, the corresponding rate of ice production, as calculated, appeared to be lower than was observed in the cloud. This suggests that other ice‐enhancement processes might be at work during the ice‐forming stage.

A small‐scale (100m) analysis of the data revealed that ice‐multiplication processes operated only in the fringes of the updraught regions of growing cells. It was also observed that a sudden occurrence of the ice usually coincided with the decay of the updraught. From these observations and from an evaluation of the amount of heat released by riming and vapour deposition processes, we suggest that the cell cores are auto‐seeded by the mixing or recycling of numerous ice crystals and that the rapid glaciation tends to be ineffective in increasing the buoyancy of the cell.