1. The Centre for Australian Weather and Climate Research A partnership between CSIRO and the Bureau of Meteorology Southern Ocean Clouds Characterization using CloudSat, CALIPSO, and the ISCCP regimes Southern Ocean Clouds and Meteorology Workshop, 27 November 2012 Alain Protat, Julien Delanoë, LATMOS John Haynes, Colorado State University Christian Jakob, Monash University

2. The Southern Ocean Clouds Problem Courtesy of J. Haynes

3. Hypothesis : Not enough low-level clouds in models The Southern Ocean Clouds Problem

4. Southern Ocean Cloud Frequency of Occurrence CloudSat-CALIPSO CFO (Mace et al. 2009) 70% of low-level clouds (underestimated) 10% of mid-level clouds 20% of high clouds 90-95% !

5. Questions The Centre for Australian Weather and Climate Research A partnership between CSIRO and the Bureau of Meteorology 1 – Why do models fail to reproduce the radiation budget in the SHB ? Is it cloud occurrence ? Statistical Overlap assumption in models in this area ? Details in the microphysical properties of low and high clouds ? 2 – Significant amounts of supercooled liquid water have been inferred from past aircraft measurements in the area. Could it explain why models behave badly in the SHB ? 3 – There is a seasonal dependence of model skills (DJF is the worst period). Why is that ? Any change in the microphysical properties ? More generally, is model skill dependent on “cloud regime” in the SHB ?

6. The cloud regimes in the SHB The Centre for Australian Weather and Climate Research A partnership between CSIRO and the Bureau of Meteorology Haynes et al. (JCLIM 2010) : 8 cloud regimes have been identified (ISCCP histograms) S1,S2 : low-topped clouds S3,S4,S5 : middle-topped clouds S6 : high-topped clouds, moderate OT S7 : midlatitude precip systems S8 : cirrus North part of SHB : S1, S2 South part of SHB : S4, S5

7. Thermodynamic phase : CloudSat-CALIPSO The Centre for Australian Weather and Climate Research A partnership between CSIRO and the Bureau of Meteorology Temperature model (ECMWF) => Ice / Liquid water Simple method : Different response of radar and lidar in presence of supercooled liquid water: Very strong lidar extinction where there is no specific radar signal Delanoë and Hogan (2010, JGR) : DARDAR Courtesy of J. Delanoë, LATMOS

8. Colocating ISCCP regimes / DARDAR Mask The Centre for Australian Weather and Climate Research A partnership between CSIRO and the Bureau of Meteorology Period available (DARDAR+ISCCP regimes) : 200606 to 200806 (2 years) Time resolution : 3 h

9. Cloud Phase versus Cloud Regime The Centre for Australian Weather and Climate Research A partnership between CSIRO and the Bureau of Meteorology 70% of ice, up to 80-90% for S6, S7, S8 Large variability among regimes More slw and ice+slw in regimes S3, S4, S5 Up to 10-15% of rain in most regimes

10. Ice microphysics versus Cloud Regime The Centre for Australian Weather and Climate Research A partnership between CSIRO and the Bureau of Meteorology S1 : 13 % (37) S2 : 3 % (8) S3 : 2 % (10) S4 : 11 % (10) S5 : 16 % (12) S6 : 22 % (10) S7 : 30 % (10) S8 : 2 % (4) CloudSat is not sensitive enough to detect all SHB clouds (probably S1 low-level clouds) Regime dependence of statistical microphysical properties is generally large Modal value of effective radius is very variable from one regime to the next. Z Z N0* Re  IWC    N0* Re Probability distribution functions (PDFs)

11. Ice microphysics versus Cloud Regime The Centre for Australian Weather and Climate Research A partnership between CSIRO and the Bureau of Meteorology Regime dependence of the mean vertical profile of all microphysical properties is large Z Z N0* Re  IWC    N0* Re Mean Vertical Profiles

12. Next steps The Centre for Australian Weather and Climate Research A partnership between CSIRO and the Bureau of Meteorology Regime dependence of low-level cloud microphysical properties (which retrieval method ?) Seasonal and spatial distributions of the regime dependence of cloud microphysics Evaluate if the ACCESS model parameterizations reproduce this observed variability as a function of season, spatial distribution, and cloud regime

13. Thank you Alain Protat Southern Ocean Clouds Characterization using CloudSat, CALIPSO, and the ISCCP regimes Email: a.protat@bom.gov.au Thank you