CLARIFY-2016 Cloud characterisation and aerosol-cloud-interaction flight planning Steven Abel, 29 th February 2016, Birmingham

Strawman flight plans 1. Cloud characterisation Sc cloud and BBA separated in the vertical - expect this to occur frequently. Flight would aim to characterise the BBA and MBL aerosol, MBL structure and cloud properties. Useful for model evaluation and semi-direct studies. Could also provide data for the direct radiative effect of aerosol above cloud.

2. BBA entrained into top of Sc More of a focus on cloud top region – expect this to occur episodically and model forecasts will be key to position the aircraft. Look for evidence of BBA in-cloud (CVI) and/or sub-cloud layer

Example profiles from SAFARI Flight A787- Keil and Haywood (2003) Clear slot above Sc typically observed Cloud drop conc = 150 cm -3 Clear slot often a vertically thin layer  need to focus on cloud top region when looking at BBA entrainment Slightly elevated aerosol and CO sitting on top of Sc  BBA entrained into cloud top? Cloud drop conc = 200 cm -3

Mid-level cloud Mid-level cloud at the top of the BBA layer – expect this to occur episodically but possibly easier to forecast from the model than BBA entrained into Sc.

Mid-level cloud Example from SAFARI-2000 flight A788 Mid-level cloud encountered on profile out of Windhoek. Cloud top temperature -14 C

Precipitation susceptibility Proposal: Precipitation susceptibility (dlnP/dlnN ccn ) will be determined from measurements of precipitation rate, cloud water contents, cloud thickness and CCN concentrations. Compositing of cloud columns with a given thickness (or LWP) allows derivation of the relation between changes in precipitation and aerosol perturbations. Is this achievable? Requires decent statistics in varying precipitation and aerosol condtions. Suggestion: Have a standard run that is done as often as possible on every sortie where there is Sc – transits, radiation flights where there is cloud etc. Run 500 ft below cloud base to measure Precipitation rate from particle size distribution LWP from MARSS radiometer Aerosol concentration from PCASP or CCN If we get enough statistics then can calculate dlnP/dlnN ccn as a function of LWP Assumes cloud drops formed on MBL aerosol i.e. Not entrained BBA.

Co-ordination with LASIC AMF at Ascension on transit scanning radar boundary-layer RHIs towards documenting cloud vertical structure ~200 deg view. est. 5 km range at 1.5 deg elevation hits cloud base Good chance we will observe shallow Cu instead of Sc. Flight in co-ordination with radar

Questions?

365 m view offshore from ARM site

FAAM aircraft range (5 hr flight) Rings show approximate time available on task with a transit at either 5 kft or 24 kft