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CCI Cloud AssessmentMark Ringer, Met Office Hadley Centre

CMUG 4th Integration meeting, Exeter – June 2nd – 4th, 2014

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Introduction

• CCI clouds produces a range of cloud parameters: cloud amount, cloud liquid water, cloud effective radius, etc

• Includes merged (all sensors) and individual sensor products (AATSR, MODIS, AVHRR)

• Phase 1 prototype data set covers 2007 – 2009

• Product definitions correspond to GEWEX cloud assessment – not specifically model-oriented

• We previously used ISCCP as a precursor data set

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General comments – comparison with other cloud data sets

• Cloud amount underestimated over global oceans

• High-level cloud underestimated over land in tropics and mid-latitudes

• Low-level cloud underestimated over sub-tropical oceanic stratocumulus areas (e.g. California, Peru)

• Large underestimate of thin cirrus cloud (algorithm? channel selection?)

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Cloud liquid water CCI vs. other data sets: JJA 2007

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Cloud liquid waterHadGEM2 vs. obs: JJA 2007

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Cloud droplet effective radius CCI merged product: JJA 2007

OBS

MODEL

– OBS

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Cloud droplet effective radius CCI individual sensor products

OBS

MODEL

– OBS

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Comments

• Interpretation of model simulation depends on data set being used for comparison

• We need to understand how/why CCI differs from other data sets of comparable cloud parameters

• Why is LWP closer to SSM/I?

• Why is CCI MODIS/ATSR different from standard MODIS/ATSR products?

• Interpretation of merged products?

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Phase 2 – modelling perspective

• A long-term record suitable for identifying trends in cloud would be of great interest…but there are risks

• Could also focus on interannual variability & model evaluation/development to show value of CCI

• Consider relation to large amount of current & future work in this area, e.g. CFMIP, WCRP grand challenge on clouds, circulation & climate sensitivity

• Specific model-oriented products may be required

• Merged products unlikely to be of use to modellers – emphasis on forward-modelling individual sensors (COSP)

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Interannual variability1997-98 ENSO: Models vs. ISCCP