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Cloud Microphysical-Dynamical Processes

Cloud Microphysical-Dynamical Processes. 25 August. 25 August: Lower cloud coupled to surface for the full case. Radiatively shaded lower cloud. Contributions from above and below. Growth of the well-mixed layer. 25 August: Radiatively-shaded lower cloud.

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Cloud Microphysical-Dynamical Processes

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  1. Cloud Microphysical-Dynamical Processes

  2. 25 August

  3. 25 August: Lower cloud coupled to surface for the full case. Radiatively shaded lower cloud Contributions from above and below Growth of the well-mixed layer

  4. 25 August: Radiatively-shaded lower cloud Upper cloud leaves and cloud starts to radiatively cool generating turbulence Thermal plumes Turbulent layer growth

  5. ASCOS: 25 August, looking at specific time periods

  6. 25 August – ½ hour average profiles Turbulence from surface initially, moving towards cloud generated More turbulence and W variance over time Skewness becoming less Shallow well-mixed layer, increasing in depth over time Peak liquid right after upper cloud goes away interpolated More ice later in case

  7. 25 August – single-layer, surface-coupled stratocumulus Correlation between vertical velocity and microphysics

  8. 25 August – single-layer, surface-coupled stratocumulus ~6 km 0.7-2 km

  9. 25 August – The difference between these is radiative shading.

  10. 27 August & 28 August De-coupled De-coupled Coupled Why skewness increase at top? Cloud top driven circulations mix down leading to coupling w/ surface Matches at 300m Abrupt transition

  11. 27 August & 28 August De-coupled De-coupled Coupled Ice production increases with the coupling…. but doesn’t decrease after de-coupling

  12. 27 August & 28 August – 1 hour average profiles Turbulence maximized near top in “decoupled” but approximately constant w/ height for “coupled” Skewness more negative for decoupled and more positive for coupled interpolated Thermal structure supports coupling vs. decoupling analysis Microphysics is variable, possibly higher peak values when coupled

  13. 27 August & 28 August – Not many clear correlations for any of the time periods

  14. 27 August & 28 August – Timeseries analyses

  15. 26 August: Why the variable ice production?

  16. EXTRA SLIDES

  17. Context: Barrow in Fall Motions at multiple wavelengths Ice forms in updrafts near cloud top, falls out. Liquid persists throughout cycle, supported by almost complete ice fallout

  18. Context: Barrow in Fall Dominant scales: 0.7 – 10 km Dominant scales: 2 – 10 km

  19. A conceptual model for Arctic fall stratocumulus • Updraft • Cloud top lifts • LWC near adiabatic • Ice particle nucleation • Limited ice concentration • IWC maximum near liquid base • Downdraft • Cloud top descends • LWC sub-adiabatic (evaporation) • Ice particles fall out • IWC negligible

  20. More Large Drops in Cleaner Clouds

  21. Polluted Case • prevalent riming • narrow droplet distribution • low ice crystal concentrations 2 mm

  22. Clean Case • little riming • broad droplet distribution • high ice crystal concentrations 2 mm

  23. Cold Polluted (over Clean) Case • In Polluted Clouds • 10-100 times fewer ice crystals • few large droplets present polluted clean

  24. Cold Polluted (over Clean) Case • In Polluted Clouds • more riming 6 mm 6 mm 6 mm

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