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