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Steven Siems 1 and Greg McFarquhar 2 1 Monash University, Melbourne, VIC, Australia

Observations of supercooled liquid water from in-situ and remote sensing observations. Steven Siems 1 and Greg McFarquhar 2 1 Monash University, Melbourne, VIC, Australia 2 University of Illinois, Urbana, IL, USA.

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Steven Siems 1 and Greg McFarquhar 2 1 Monash University, Melbourne, VIC, Australia

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  1. Observations of supercooled liquid water from in-situ and remote sensing observations Steven Siems1 and Greg McFarquhar2 1Monash University, Melbourne, VIC, Australia 2University of Illinois, Urbana, IL, USA Workshop on Clouds, Aerosols, Radiation and Air-Sea Interface of Southern Ocean: Establishing Directions for Future Research, 18-19 March 2014, Seattle, WA

  2. Mixed phase clouds occur regularly in Arctic/ Southern Oceans, especially in the spring & fall Supercooled water contents large enough that they can cause aircraft instruments to ice up in Arctic

  3. Mixed phase clouds occur regularly in Arctic/ Southern Oceans, especially in the spring & fall Supercooled water contents large enough that they can cause aircraft instruments to ice up in Arctic We also know that they occur over the Southern Oceans, yet there are not as much in-situ data

  4. Mixed phase clouds occur regularly in Arctic/ Southern Oceans, especially in the spring & fall Supercooled water contents large enough that they can cause aircraft instruments to ice up in Arctic Why do these clouds persist?

  5. Mixed phase clouds occur regularly in Arctic/ Southern Oceans, especially in the spring & fall Supercooled water contents large enough that they can cause aircraft instruments to ice up in Arctic How do aerosols affect these mixed-phase clouds

  6. Mixed phase clouds occur regularly in Arctic/ Southern Oceans, especially in the spring & fall Supercooled water contents large enough that they can cause aircraft instruments to ice up in Arctic Pristine conditions over Southern Oceans provide good contrast to existing Arctic observations

  7. Aerosol Impacts on Mixed-Phase Clouds Glaciation indirect effect (Lohmann 2002) Riming indirect effect (Borys et al. 2004) Thermodynamic indirect effect (Rangno & Hobbs 2001; Lance et al. 2011

  8. Arctic Experiments Review past Arctic experiments to understand what data needed to study supercooled/mixed-phase clouds over Southern Oceans

  9. M-PACE: Sept. 27 to Oct. 22 2004 Objective: Collect focused set of observations to advance understanding of dynamical and microphysical processes in mixed-phase clouds, including radiative transfer through clouds Analysis of > 100 vertical profiles conducted

  10. Vertical profiles of Ni & Nw generated from measurements as function of normalized altitude (Zn) used to develop/evaluate models & retrievals

  11. 1 Fridlind et al. 2007 zn 0 1 zn 0 Poor agreement between modeled & measured IWC & ice crystal concentration

  12. 1 1 Fridlind et al. 2007 zn zn 0 0 1 1 zn zn 0 0 Better agreement between modeled & observed ice concentration when have 1) formation of ice nuclei from drop evaporation residuals 2) drop freezing during evaporation 1 zn 0 Ice # [L-1]

  13. M-PACEOctober 2004 Pristine Conditions Open ocean Few cloud droplets Ice multiplication Precipitation Polluted Conditions Sea Ice Many cloud droplets Ice nucleation Little precipitation ISDACApril 2008

  14. NRC NAX radar X band radar Z and Vd crossections

  15. Strong capping inversion between normalized altitude (zn) of 0.8 to 1.2

  16. Strong capping inversion between normalized altitude (zn) of 0.8 to 1.2 Subadiabatic LWC for zn > 0.8 consistent with entrainment of dry air above cloud top or growth of ice at expense of liquid water

  17. Controls of Cloud Properties • Examined dependence of cloud properties on aerosol amounts above and below cloud base for different surface and meteorological conditions • Assessed importance of different indirect effects • Although needed more data, some patterns emerged

  18. ISDAC M-PACE Normalized Frequency

  19. ISDAC M-PACE Normalized Frequency LWC < for ISDAC than M-PACE, consistent with more open water during M-PACE

  20. ISDAC M-PACE Normalized Frequency

  21. ISDAC M-PACE Normalized Frequency Nliq > for ISDAC than M-PACE, consistent with presence of more aerosols/CCN

  22. ISDAC M-PACE Normalized Frequency

  23. ISDAC M-PACE Normalized Frequency rel < for ISDAC than M-PACE,

  24. ISDAC M-PACE Normalized Frequency Nice < for ISDAC than M-PACE, consistent with thermoynamic indirect effect

  25. Southern Ocean Data • Need equivalent set of data over Southern Oceans to understand why these clouds persist and to advance our understanding of dynamical & microphysical processes in mixed-phase clouds, including radiative transfer • Need in-situ cloud microphysics, in-situ aerosols and remote sensing to give context of measurements

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