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

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 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? 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 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 Mixed phase clouds occur regularly in Arctic/ Southern Oceans, especially in the spring & fall

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

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

M-PACE: Sept. 27 to Oct 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 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

Vertical profiles of N i & N w generated from measurements as function of normalized altitude (Zn) used to develop/evaluate models & retrievals

Poor agreement between modeled & measured IWC & ice crystal concentration Fridlind et al znzn znzn

Better agreement between modeled & observed ice concentration when have 1) formation of ice nuclei from drop evaporation residuals 2) drop freezing during evaporation znzn znzn znzn znzn znzn 0 1 Ice # [L -1 ]

M-PACE October 2004 Pristine Conditions –Open ocean –Few cloud droplets –Ice multiplication –Precipitation Polluted Conditions –Sea Ice –Many cloud droplets –Ice nucleation –Little precipitation ISDAC April 2008

NRC NAX radar X band radar Z and V d crossections NRC NAX radar X band radar Z and V d crossections

Strong capping inversion between normalized altitude (z n ) of 0.8 to 1.2

Subadiabatic LWC for z n > 0.8 consistent with entrainment of dry air above cloud top or growth of ice at expense of liquid water

-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 Controls of Cloud Properties

ISDACM-PACE

ISDACM-PACE LWC < for ISDAC than M-PACE, consistent with more open water during M-PACE

ISDACM-PACE

ISDACM-PACE N liq > for ISDAC than M-PACE, consistent with presence of more aerosols/CCN

ISDACM-PACE

ISDACM-PACE r el < for ISDAC than M-PACE,

ISDACM-PACE N ice < for ISDAC than M-PACE, consistent with thermoynamic indirect effect

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