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Altocumulus Cloud Sortie Paul Barrett, Phil Brown, Alan Blyth © Crown copyright Met Office Altocumulus Sortie – PiknMix 2014 Mixed Phase supercooled layer cloud measurements in the mid-troposphere • • • Motivation: Investigate the turbulence and ice properties in supercooled altocumulus clouds Typical Weather conditions: Frontal systems: • ahead of warm fronts • within humid warm sectors • occluding fronts • within large scale upper troughs (500hPa down to 800hPa) • No embedded waves Cloud Top Temperature • -10°C to -30°C (ideal -20°C) © Crown copyright Met Office Key Instruments: (possible Go / no-go) • AIMMS / 5-port turbulence, • CDP, SID2, CIP15/100, 2DC, WVSS2, TWC, Nevzorov Nice to have: • • • LIDAR, Dropsonde, Video, MARSS, BCPd, 3V-CPI, Aerosol Measurements – PCASP, GRIMM, CPC, CAS? T-Amdar (icing, humidity) Altocumulus Model and Flight Strategy • Cellular Liquid Cloud structure underneath temperature inversion – very thin liquid layer <1000ft • Ice virga falling from liquid layer • Turbulence Structure c.f. Stratocumulus • Sloping Cloud top along constant potential temperature surfaces – difficult to fly through! © Crown copyright Met Office Flight Strategy • • • • • • • SLRs become “slant” profiles w.r.t inversion altitude – 1,3,4,7 dog-leg stack of straight and level runs: Along and across wind legs Profiles, wings level, at 1000ft/min to minimise horizontal contam. of vertical structure Aircraft to drift with the wind LIDAR to measure CTH If high LWC expected then Cloud Top Runs last! (warmer clouds) Sample the inversion at regular intervals in time and space B674 Altitude Time Series N © Crown copyright Met Office S N S N S