1. The Centre for Australian Weather and Climate Research A partnership between CSIRO and the Bureau of Meteorology Southern Ocean cloud biases in ACCESS and improvements Charmaine Franklin 27 November 2012 www.cawcr.gov.au

2. The Centre for Australian Weather and Climate Research A partnership between CSIRO and the Bureau of Meteorology satellite simulators Diagnosing cloud processes in climate models with observations is difficult and fraught with issues – Correspondence of model quantities to available observations – Limitations of satellite observations – Scale of model grids (~100 km) vs. satellite pixels (~1 km) Simulators reduce the effects of these issues so that comparisons between models and observations more likely are an evaluation of the model The simulator is a piece of diagnostic code that mimics the observational process by converting model variables into pseudo- satellite observations What would a satellite see if the atmosphere had the clouds of a climate model?

3. The Centre for Australian Weather and Climate Research A partnership between CSIRO and the Bureau of Meteorology satellite simulator schematic model output fields observed radiances simulated radiances retrieval algorithm retrieved satellite fields downscaler and forward model simulated satellite fields satellite simulator climate model satellite instruments

4. The Centre for Australian Weather and Climate Research A partnership between CSIRO and the Bureau of Meteorology CFMIP Observational Simulator Package COSP takes model grid box mean vertical profiles and breaks these into subcolumns that represent areas similar to a satellite pixel Subgrid profiles are used in instrument simulators to simulate retrievals Statistical routines compute diagnostics that can be compared with satellite observations CFMIP = Cloud Feedback Model Intercomparison Project COSP schematic from Bodas-Salcedo et al. 2011 BAMS

5. The Centre for Australian Weather and Climate Research A partnership between CSIRO and the Bureau of Meteorology ACCESS1.3 Proto-type HadGEM3 (Hewitt et al. 2011 GMD) prognostic cloud, prognostic condensate: PC2 revised calculation of parcel perturbations for shallow convection – more consistent vertical fluxes between BL and convection RH based CAPE closure “buddy” scheme used at coastal gridpts that separates near surface winds into land and ocean components – improves precip over maritime continent CABLE land surface scheme Modifications to clouds and radiation: Ice cloud fraction parameterisation (Franklin et al. 2012 QJ) Triplecloud scheme to account for cloud horizontal inhomogeneity in radiative transfer calculations (Shonk et al. 2010 QJ) Area cloud fraction scheme to account for effects of coarse vertical resolution (Boutle and Morcrette 2010 ASL) Changes in the air-sea flux parameterisation (Fairall et al. 2003)

6. The Centre for Australian Weather and Climate Research A partnership between CSIRO and the Bureau of Meteorology ACCESS1.3 AMIP model evaluation

7. The Centre for Australian Weather and Climate Research A partnership between CSIRO and the Bureau of Meteorology cloud fraction djf 2006-2007 50 – 440 hPa 440 –680 hPa > 680 hPa

8. The Centre for Australian Weather and Climate Research A partnership between CSIRO and the Bureau of Meteorology cloud fraction jja 2007

9. The Centre for Australian Weather and Climate Research A partnership between CSIRO and the Bureau of Meteorology cloud/hydrometeor occurrence zonal mean

10. The Centre for Australian Weather and Climate Research A partnership between CSIRO and the Bureau of Meteorology cloud radiative effect Subtracting the clear sky fluxes from total gives a measure of cloud effects on outgoing radiation: reverse the sign so the effect is into the climate system

11. The Centre for Australian Weather and Climate Research A partnership between CSIRO and the Bureau of Meteorology cloud radiative effect error (djf and jja 2007)

12. The Centre for Australian Weather and Climate Research A partnership between CSIRO and the Bureau of Meteorology evaluation of regional cloud properties Radar reflectivity A measure of the efficiency of a radar target in intercepting and returning radio energy. It depends upon the size, shape, aspect, and dielectric properties of that target Proportional to particle diameter to the sixth power in the Rayleigh scattering regime Lidar scattering ratio Lidar is a similar principle to radar - pulses of light emitted into the atmosphere are scattered back by clouds, aerosols or air molecules Scattering ratio defined as the ratio of the total backscatter / molecular backscatter (backscatter if no clouds or aerosols), SR > 5 = clouds Proportional to particle radius squared ISCCP cloud optical depth Amount of light cloud droplets or ice particles prevent from passing through a column of atmosphere. Derived from retrievals that use visible and infrared radiances

13. The Centre for Australian Weather and Climate Research A partnership between CSIRO and the Bureau of Meteorology southern ocean djf2007 40 – 60S, 130 – 175W

14. The Centre for Australian Weather and Climate Research A partnership between CSIRO and the Bureau of Meteorology southern ocean

15. The Centre for Australian Weather and Climate Research A partnership between CSIRO and the Bureau of Meteorology model developments: ice fall speeds Franklin et al. (2012) identified that PC2 produces large in-cloud water contents and faster falling ice particles in mid-lower levels ACCESS climate set up uses 1 ice prognostic but this is split diagnostically by temperature to represent 2 hydrometeor types: small ice crystals and large aggregates - snow

16. The Centre for Australian Weather and Climate Research A partnership between CSIRO and the Bureau of Meteorology

17. integrated histograms

18. The Centre for Australian Weather and Climate Research A partnership between CSIRO and the Bureau of Meteorology cloud radiative effect djfSW (rmse, bias)LW (rmse, bias)net (rmse, bias) global ctl23.5, 4.812.9, -0.320.2, 4.5 global fall22.7, 5.012.4, -1.019.6, 4.0 SO ctl24.7, 17.914.3, 0.520.0, 18.3 SO fall23.4, 16.313.7, 0.118.9, 16.7

19. The Centre for Australian Weather and Climate Research A partnership between CSIRO and the Bureau of Meteorology summary ACCESS1.3 SO evaluation: total cloud cover underestimated by up to 20% low -8%, mid -12%, high +2% SW and net cloud radiative effect underestimated in djf by 18 Wm -2 High clouds: Good comparison with CloudSat cloud fraction with but due to too many low radar reflectivities not enough large – ice particle sizes underestimated Too much high cloud fraction compared to CALIPSO and not enough occurrences of large scattering ratios – ice water content underestimated Low clouds < 2 km: not enough condensate and non-precipitating cloud, too much rain and drizzle ISCCP: Not enough optically thick clouds at all heights Changing ice fall speeds shows some improvements: increases frequency of occurrence of large SR and optically thick clouds, particularly at correct height

20. The Centre for Australian Weather and Climate Research A partnership between CSIRO and the Bureau of Meteorology Charmaine Franklin Email: charmaine.franklin@csiro.au Web: www.cawcr.gov.au Thank you www.cawcr.gov.au