© crown copyright met office cci cloud assessment mark ringer, met office hadley centre cmug 4 th...
TRANSCRIPT
© Crown copyright Met Office
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 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)