A methodology for the comparison of blocking climatologies across indices, models and climate scenarios

There is urgent need for a consistent blocking identification method that can be used and compared across reanalyses, models and climate scenarios. We present such a method and diagnose daily blocking frequency in 43 years (1958–2000) of ERA-40 Reanalysis for indices defined on both the commonly use...

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Bibliographic Details
Published in:Climate dynamics 2012-06, Vol.38 (11-12), p.2467-2481
Main Authors: Barnes, Elizabeth A., Slingo, Julia, Woollings, Tim
Format: Article
Language:English
Subjects:
Atmospheric circulation
Climate change
Climate models
Climatology
Climatology. Bioclimatology. Climate change
Cyclones
Earth and Environmental Science
Earth Sciences
Earth, ocean, space
Exact sciences and technology
External geophysics
Geophysics/Geodesy
Global warming
Greenhouse gases
Meteorology
Oceanography
Simulation
Wind
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Summary:There is urgent need for a consistent blocking identification method that can be used and compared across reanalyses, models and climate scenarios. We present such a method and diagnose daily blocking frequency in 43 years (1958–2000) of ERA-40 Reanalysis for indices defined on both the commonly used geopotential height and potential temperature fields as well as a zonal wind index. Applications of various blocking indices to the same data highlights the importance of a consistent methodology for comparison and a method that identifies blocks along a path that varies with the latitude of the storm track. Since the method accommodates blocking detection using 500 mb zonal-wind which is readily available in climate model output, we diagnose blocking in 14 CMIP3 models under two different greenhouse gas scenarios. Blocking duration remains nearly constant among the scenarios, but a robust reduction in blocking frequency with global warming is demonstrated.
ISSN:0930-7575
1432-0894
DOI:10.1007/s00382-011-1243-6