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Unveiling Reanalyses: Insights, Challenges, and Applications

Discover the world of reanalyses - the retrospective analysis combining historical observations with model forecasts to generate valuable time-series data. Learn about its uses, potential issues, and key resources. Explore applications in climate modeling, intercomparisons, and addressing biases. Delve into crucial topics like data assimilation methods and uncertainties. Find useful resources for data download, visualization, and comparison. Uncover the secrets and intricacies of reanalyses today!

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Unveiling Reanalyses: Insights, Challenges, and Applications

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  1. Reanalyses – A sharing of juicy tidbits* and gory details** Andrew Klekociuk, Australian Antarctic Division * a choice or pleasing bit of anything, as gossip.** to tell all the small details about something that is unpleasant or interesting in a shocking way.

  2. Outline • A Brief Introduction to Reanalyses • Uses • Potential Issues • Resources

  3. Reanalysis = Retrospective Analysis • Observations taken over a long time period are combined objectively with a model forecast to form time-series of fields representing the state of the system. • Observations: • Atmosphere: pressure, temperature, wind humidity. • Ocean: pressure, temperature, currents, salinity.

  4. Reanalysis = Retrospective Analysis • Model is kept constant over entire time period (though quality, density and type of observations can change). • Differs from ‘operation analysis’ where the model may change. • Data assimilation fills gaps. • The best resource – http://reanalyses.org/

  5. Key Reanalyses • Atmosphere – http://reanalysis.org/atmosphere/overview-current-reanalyses • ECMWF(European Centre for Medium-Range Weather Forecasts) • NCEP/NCAR(National Centers for Environmental Prediction, National Center for Atmospheric Research) • Oceans – http://reanalysis.org/ocean/overview-current-reanalyses • NCEP CFSR (Climate Forecast System Reanalysis)

  6. Applications • Climate Model Intercomparisons Bias with respect to ERA-40, averaged over 1980-2000 ACCESS = Australian Community Climate and Earth System Simulator

  7. Potential Issues • Data Assimilation/Filtering/Interpolation Methods: 4-dimensional variational analysis (4D-var) vs other approaches. • Treatment of uncertainties (Gaussian) • http://earth.esa.int/dragon/D5_L1_Elbern.pdf

  8. Potential Issues • What observational data are used? ERA-Interim: Dee et al., QJRMS 2011, Fig 10

  9. ERA-Interim Ozone Measurements ERA-Interim: Dee et al., QJRMS 2011, Fig 15

  10. Total Column Ozone

  11. ERA-Interim Surface Pressure Surface Pressure ERA-Interim: Dee et al., QJRMS 2011, Fig 17

  12. Other Reanalyses of Interest • MACC (Monitoring Atmospheric Composition and Climate) http://www.gmes-atmosphere.eu/d/services/gac/reanalysis/macc • 20th Century Reanalysishttp://www.esrl.noaa.gov/psd/data/20thC_Rean

  13. Useful Resources • Downloading data – local servers (e.g. NCI) vs remote servers (e.g. http://apps.ecmwf.int/datasets) • Data viewers (e.g. Panopoly for HDF, GRIB, NetCDF - http://www.giss.nasa.gov/tools/panoply) • Web-based Reanalysis Intercomparison Tools (WRIT) - http://reanalyses.org/atmosphere/writ • NCO Tools http://nco.sourceforge.net

  14. Useful Resources • Climate Atlases – e.g. MERRA (Modern Era Retrospective-analyses for Research Applications) http://gmao.gsfc.nasa.gov/ref/merra/atlas/menu.php • Climate Explorer http://climexp.knmi.nl • Climate Data Library http://iridl.ldeo.columbia.edu • Climate Reanalyserhttp://cci-reanalyzer.org • Local Resources

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