Measurements of microphyscs in cold air Outbreks

Measurements were made in 2 sets of cold air outbreaks using the UK FAAM BAE 146  research aircraft. The first set were performed in March 2022 over the Eastern Atlantic the second set were perform in October to early November 2022 in the Western Atlantic over the Labrador Sea based in Goose Bay, Eastern Canada. In each set of experiments the focus was to study the evolution of the cloud microphysics as influenced by Cloud condensation nuclei, ice nuclei and secondary ice processes  in the stratocumulus clouds being advected southwards over progressively warmer sea until cloud break-up occurred into convective clouds. The aims were to improve the treatment of these cloud types in Global climate models and weather forecast models. These projects formed part of m-Phase funded by NERC as part of its Cloud Sense programme and ACAO a Met office program to study these clouds.A range of aerosol and cloud microphysical equipment was used in the 2 projects which will be discussed in the presentation.Analysis of the data set including a new novel Holographic instrument is still underway at the time of writing; however, some preliminary results indicate that:

• Generally the ice crystal number concentration exceeded the ice nucleus concentrations measured at the same temperature
• Some regions consisted entirely of super cooled water
• A range of secondary ice particle production mechanisms were observed including ice splinter production during riming and droplet shattering on freezing after capture by ice crystals
• Generally if the convective region was reached by the aircraft then secondary ice production was greater than in the stratocumulus region
• Precipitation was mostly in the ice phase