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


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


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


Period available (DARDAR+ISCCP regimes) : 200606 to 200806 (2 years)

Time resolution : 3 h

Cloud Phase versus Cloud Regime


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


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


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


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

Alain Protat, Julien Delanoë, LATMOS John Haynes, Colorado State University

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