Radar observations of the microphysical properties of convective clouds observed in the UK during the CSIP campaign

Microphysical processes are believed to play a crucial role in the development and secondary initiation of precipitating convective clouds. A wide variety of microphysical situations occurred in convective clouds observed during the Convective Storm Initiation Project (CSIP), held during July 2004 and June-August 2005 in southern England. The convective clouds were observed principally with the dual-polarisation, Doppler S-band radar and the Doppler L-band radar on the Chilbolton 25-m dish. A large array of instruments and facilities was also deployed during CSIP, including two light aircraft, a wind profiler, two Doppler lidars, several radiometers and six mobile radiosonde stations. Radiosondes were released at a frequency of up to one per hour during intensive operation periods. In addition the BAE 146 FAAM aircraft flew in the vicinity of the Chilbolton radars as part of the ICEPIC (ICE and Precipitation Initiation in Cumulus) campaign.

It was found that rain fell from some warm clouds no more than 1 km deep, while on other days, almost no rain fell from clouds that were more than 4 km deep, with tops colder than about -10 C. The UK Met Office Unified Model over-predicted the amount of precipitation in the latter situation. On at least one day the first precipitation in clouds consisted of a small concentration of large drops. The microphysics observations from the radar and aircraft will be presented in this talk in the context of the other extensive observations and the UM results.