On the relation between albedo, cloud fraction and aerosol optical depth in climate models and satellite observations

Transcription

1 On the relation between albedo, cloud fraction and aerosol optical depth in climate models and satellite observations Frida Bender, Anders Engström, Johannes Karlsson Department of Meteorology and Bolin Centre for Climate Research

2 Image courtesy of NASA

3 Stratocumulus cloud albedo albedo cloud frac4on 1

4 Stratocumulus cloud albedo albedo α clear cloud frac4on 1

5 Stratocumulus cloud albedo albedo α clear cloud frac4on 1

6 Stratocumulus cloud albedo albedo α clear cloud frac4on 1

7 Stratocumulus cloud albedo albedo α clear cloud frac4on 1

8 Stratocumulus cloud albedo albedo α clear cloud frac4on 1

9 Stratocumulus cloud albedo α cloud albedo α clear cloud frac4on 1

10 Stratocumulus cloud albedo α cloud albedo α clear cloud frac4on 1

11 Stratocumulus cloud albedo in observations and models Satellite observa4ons CERES/MODIS Bender et al. 2011

12 Stratocumulus cloud albedo in observations and models 2 CMIP3 models Satellite observa4ons CERES/MODIS Bender et al. 2011

13 Improved representation in CMIP5 models rnian c ACCESS1 0 ACCESS1 3 BNU ESM CESM1 CAM5 GFDL CM3 GFDL ESM2G GFDL ESM2M GISS E2 R HadGEM2 CC HadGEM2 ES IPSL CM5A LR IPSL CM5A MR IPSL CM5B LR MIROC4h MIROC5 MIROC ESM CHEM MIROC ESM MRI CGCM3 NorESM1 ME NorESM1 M MPI ESM LR CCSM4 CanESM2 BCC CSM1 1 CNRM CM5 INM CM44 Ensemble mean Aqua Terra Peruvian , alian r CF, Engström et al Namibian

14 Present-day clouds are brighter than pre-industrial clouds Californian 5 5 Peruvian PI (before 1850) and HIST ( ) cloud albedo differ by ~0.01 x PI Albedo x PI x HIST 0.05 x HIST.2 1 Cloud Fraction Australian Engström et al Cloud Fraction Namibian

15 Present-day clouds are brighter than pre-industrial clouds Californian 5 5 Californian 5 5 Peruvian Peruvian Albedo 5 Albedo x PI x HIST x PI x HIST Cloud Fraction Australian Cloud Fraction Namibian 5 Albedo CMIP5 models 5 25 yrs PI (before 1850) 25 yrs historical ( ) equally spaced 0.05 CF- bins x PI x HIST Albedo Albedo x PI x HIST Cloud Fraction 5 Canarian Cloud Fraction x PI x PI Albedo x HIST x HIST 0 0 Cloud Cloud Fraction 1 Australian x PI Engström et al Fig. 6. Scatter plots and slopes from the linear regression between cloud fraction and total x HIST 0 1 Cloud Fraction Namibian

16 Are polluted clouds brighter? Idealized model: Clean (Nd=75cm - 3 ) and polluted (Nd=150 cm - 3 ) cloud albedo differ by 0.04 Simple model

17 Satellite data GCM output 10 years of monthly mean data: albedo, cloud frac4on and AOD CERES and MODIS Mean of 20 CMIP5 models, Morning and afternoon normalized to ensemble mean overpasses Full day sampled MODIS cloud-free AOD All-sky AOD De- seasonalized De- regionalized AOD anomaly

18 Are polluted clouds brighter? Simple model Satellite observa4ons CERES/MODIS Simple model CMIP5 mul4- model mean

19 Are polluted clouds brighter? Satellite observa4ons CERES/MODIS Simple model CMIP5 mul4- model mean

20 Summary Regional stratocumulus cloud albedo can be determined from total albedo and cloud fraction Agreement with observations improved from CMIP3 to CMIP5 models Increase in cloud albedo in CMIP5 models from pre-industrial to present day likely due to aerosol CMIP5 models have higher cloud albedo at higher aerosol loading, an effect not seen in satellite observations

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22 Idealized model CCN AOD Andreae (2009) Jones at al. (2001) N d Parameter sampled from observed distribu4on Parameter corresponding to data/gcm- output LWP Wood (2012) τ Cor4 & Peter (2009) α cloud α = α cld f + α clr (1 - f ) f α

23 Improved representation in CMIP5 models rnian c c ACCESS1 0 ACCESS1 3 BNU ESM CESM1 CAM5 GFDL CM3 GFDL ESM2G GFDL ESM2M GISS E2 R HadGEM2 CC HadGEM2 ES IPSL CM5A LR IPSL CM5A MR IPSL CM5B LR MIROC4h MIROC5 MIROC ESM CHEM MIROC ESM MRI CGCM3 NorESM1 ME NorESM1 M MPI ESM LR CCSM4 CanESM2 BCC CSM1 1 CNRM CM5 INM CM44 Ensemble mean Aqua Terra Californian r CF, ACCESS1 0 ACCESS1 3 BNU ESM CESM1 CAM5 GFDL CM3 GFDL ESM2G GFDL ESM2M GISS E2 R HadGEM2 CC HadGEM2 ES IPSL CM5A LR IPSL CM5A MR IPSL CM5B LR MIROC4h MIROC5 MIROC ESM CHEM MIROC ESM MRI CGCM3 NorESM1 ME NorESM1 M MPI ESM LR CCSM4 CanESM2 BCC CSM1 1 CNRM CM5 INM CM44 Ensemble mean Aqua Terra Australian c c c 5 ACCESS1 0 ACCESS1 3 BNU ESM CESM1 CAM5 GFDL CM3 GFDL ESM2G GFDL ESM2M GISS E2 R HadGEM2 CC HadGEM2 ES IPSL CM5A LR IPSL CM5A MR IPSL CM5B LR Peruvian MIROC4h MIROC5 ACCESS1 0 MIROC ESM CHEM 5 MIROC ESM MRI CGCM3 ACCESS1 3 NorESM1 ME NorESM1 M MPI ESM LR BNU ESM CCSM4 CanESM2 BCC CSM1 1 CESM1 CAM5 CNRM CM5 INM CM44 Ensemble mean GFDL CM3 5 Aqua 5Terra GFDL ESM2G GFDL ESM2M GISS E2 R HadGEM2 CC 5 HadGEM2 ES IPSL CM5A LR IPSL CM5A MR r CF, IPSL CM5B LR MIROC4h Namibian MIROC5 ACCESS1 0 ACCESS1 3 MIROC ESM CHEM BNU ESM CESM1 CAM5 5GFDL CM3 5 MIROC ESM GFDL ESM2G GFDL ESM2M GISS E2 R MRI CGCM3 HadGEM2 CC HadGEM2 ES IPSL CM5A LR NorESM1 ME IPSL CM5A MR IPSL CM5B LR NorESM1 M MIROC4h MIROC5 MIROC ESM CHEM 5 MPI ESM LR MIROC ESM MRI CGCM3 NorESM1 ME CCSM4 NorESM1 M MPI ESM LR CCSM4 CanESM2 CanESM2 BCC CSM1 1 CNRM CM5 BCC CSM1 1 INM CM44 Ensemble mean 5 Aqua CNRM CM5 Terra INM CM44 Ensemble mean 5 Aqua 5 Terra Peruvian , alian c r CF, Canarian ACCESS1 0 ACCESS1 3 BNU ESM CESM1 CAM5 GFDL CM3 GFDL ESM2G GFDL ESM2M GISS E2 R HadGEM2 CC HadGEM2 ES IPSL CM5A LR IPSL CM5A MR IPSL CM5B LR MIROC4h MIROC5 MIROC ESM CHEM MIROC ESM MRI CGCM3 NorESM1 ME NorESM1 M MPI ESM LR CCSM4 CanESM2 BCC CSM1 1 CNRM CM5 INM CM44 Ensemble mean Aqua Terra r CF, Fig. 3. Correlation coe r CF, r CF, Engström et al Namibian cient and estimated c from the relation between albedo and total