COSMICS Cold-air outbreak sorties Steven Abel and Richard Cotton © Crown copyright Met Office

Cold-air outbreaks Cold air flow over a relatively warm sea surface leading to the formation of boundary layer stratiform and convective clouds. Model often struggles to capture these mixed phase clouds. Similar issues occur for the southern Ocean, with the lack of cloud contributing to a large SST bias in most climate models (lots of active international research in this area). Poor representation of mixed-phase cloud microphysics Poor representation of surface fluxes Unable to capture correct boundary layer structure, particularly in stratiform region.

Stratiform sorties B668: Stratiform clouds GOAL: To provide measurements of the cloud topped boundary layer in the stratiform region and the transition to open cellular convection PIKNMIX 2012: Good in-situ measurements of cloud and boundary layer structure. Model unable to capture overcast cloud in stratiform region. Well known model problem in cold-air outbreak conditions. PIKNMIX-C: Two case-studies (similar model problems in capturing cloud) PIKNMIX-D: No cases COSMICS: Iceland and Kiruna operating bases to enable additional case studies. B668: Stratiform clouds © Crown copyright Met Office

B668: PikNMix-B The transition region and stratiform regime were well characterised by in-situ measurements. Science on way to Iceland, refuel, return at high level dropping sondes (B668). B A Prestwick FL200 A B 2 km Iceland © Crown copyright Met Office

COSMICS: Required to operate from Iceland or Kiruna because stratiform and transition region further north. B A B FL200 A Norwegian Sea Greenland Sea 2 km B C Iceland Keflavik © Crown copyright Met Office

Convective sorties B667:Convective clouds GOAL: To provide comprehensive in-situ measurements of mixed-phase convective clouds in cold-air outbreak conditions for the evaluation of high resolution NWP model simulations. CONSTRAIN / PIKNMIX 2012: Significant underestimate of IWC in the model. Good cloud microphysics data but no in-cloud dynamics (icing of turbulenece probe). PIKNMIX-D: AIMMS-20 gives us the ability to look at in-cloud turbulence in the presence of supercooled water. © Crown copyright Met Office

Convective sorties Sortie will consist of: Deep profiles in cloud free conditions. Boundary layer measurements of fluxes, aerosol and precipitation A  B. Cloud penetration runs at fixed levels. Runs generally between points A and B but deviations required to maximise number of cloud penetrations. Points A and B orientated across mean wind direction © Crown copyright Met Office

Instrumentation Key Instruments Temperature, Total Water, AIMMS-20, Turbulence probe, Cloud physics (all), WVSS-II, General Eastern/Buck, Nevzorov, Dropsonde Extremely useful FAAM CCN, FAAM CPC, GRIMM, Weather radar (for convective flights), Heimann, JW Nice to have ARIES, LIDAR, Core Chem, Nephelometer, PSAP, MARSS (for stratiform flight only), Aircraft video, TAMDAR © Crown copyright Met Office