Alain Protat, Julien Delanoë, LATMOS John Haynes, Colorado State University
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Transcript of Alain Protat, Julien Delanoë, LATMOS John Haynes, Colorado State University
The Centre for Australian Weather and Climate ResearchA partnership between CSIRO and the Bureau of Meteorology
Southern Ocean Clouds Characterization using CloudSat, CALIPSO, and the ISCCP regimes
Southern Ocean Clouds and MeteorologyWorkshop, 27 November 2012
Alain Protat, Julien Delanoë, LATMOS
John Haynes, Colorado State University
Christian Jakob , Monash University
The Southern Ocean Clouds Problem
Courtesy of J. Haynes
Courtesy of J. HaynesHypothesis : Not enough low-level clouds in models
The Southern Ocean Clouds Problem
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% !
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 ?
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 cloudsS3,S4,S5 : middle-topped cloudsS6 : high-topped clouds, moderate OTS7 : midlatitude precip systemsS8 : cirrusNorth part of SHB : S1, S2South part of SHB : S4, S5
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 waterSimple 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
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
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, S8Large variability among regimesMore slw and ice+slw in regimes S3, S4, S5Up to 10-15% of rain in most regimes
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 largeModal value of effective radius is very variable from one regime to the next.
Z Z
N0*Re
IWC IWC
N0*Re
Probability distribution functions (PDFs)
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 IWC
N0*Re
Mean Vertical Profiles
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
Thank you
Alain ProtatSouthern Ocean Clouds Characterization using CloudSat, CALIPSO, and the ISCCP regimes
Email: [email protected]
Thank you