osse next steps discussion
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OSSE Next Steps Discussion
CLARREO Spring SDT Meeting Discussion
Discussion Leaders: Dan Feldman and Bill Collins
April 17, 2013
Discussion Topics
• How can OSSE calculations and analysis from CMIP5 best inform continuing CLARREO pre-Phase A activities?
• What are the most appropriate methods for sampling CMIP5 that are sufficient for exploring the science value of CLARREO?
• How should the OSSE simulations interface with existing observational datasets and the larger OSSE community?
Science Questions
• What are the science goals with CLARREO OSSE simulations of the CMIP5 archive?– Identify those (hopefully short-term) observables that
differentiate models according to their long-term climate sensitivity or feedbacks?
– Show how well existing datasets differentiate climate models and improvements with CLARREO?
CMIP5 archive sampling
• The problem: extremely large archive to sample.• Current sampling approach:
– Analyze the CFMIP first to assess potential OSSE errors, then assess the larger archive.
• Open sampling questions:– Long-term (forced response prediction) or near-term
(climate forecast) simulations?– AOGCMs or Earth System Models?
From CMIP5 OSSEs to CLARREO Science Questions
Quantity/property of interest CMIP5 Experiments
Unforced variability in the climate system
Long-duration pre-industrial runs among multiple ensemble members for a single model and forcing scenario
Comparisons against climate record
Historical and decadal simulations initialized from historical initial conditions
Signals of varying climate sensitivity
Intra-ensemble variability within a single RCP
Signals of various forcing agents
Single forcing agent simulations
Cloud spectral signatures Aqua planet, patterned/uniform delta SST, etc.
Spectral signatures of differing scenarios
Contrast across RCPs
Taylor, 2009
Data Storage and Accessibility
• Data files currently are 1.2 GB per month (SW) and 0.8 GB per month (LW) which dwarfs the input file size.
• Lossy data compression: how much error can be tolerated?
• Access to the CLARREO server for the extended scientific community?
Model-Model vs. Model-Measurement Comparisons
• Different treatments of radiation within the climate models that have reported to CMIP5.
• Measurement-model intercomparison vs model-model intercomparison.– Realism vs. consistency with model radiation– How to deal with natural variability?
OSSEs for Existing and Future Datasets
• Some hyperspectral instruments (e.g., AIRS and SCIAMACHY) have decadal-length records.
• Should OSSEs focus on existing datasets or on the value of future ones?
Interfacing with COSP
• CFMIP Observational Simulator Package (COSP) is fast and runs “inline” but with no hyperspectral capabilities.– COSP data currently underutilized.
• Opportunities for synergy between the COSP community and CLARREO OSSEs?– Enable the COSP framework to work on a much
larger number of instruments.– Build on the COSP analysis tools and frameworks
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