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Predictability of spring cold spells in Europe M. E. Shongwe, G. J. van Oldenborgh, C. Ferro and C. A. S. Coelho.

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Presentation on theme: "Predictability of spring cold spells in Europe M. E. Shongwe, G. J. van Oldenborgh, C. Ferro and C. A. S. Coelho."— Presentation transcript:

1 Predictability of spring cold spells in Europe M. E. Shongwe, G. J. van Oldenborgh, C. Ferro and C. A. S. Coelho

2 Outline Motivation Model verification Possible source of model skill Skill scores relative to a simple statistical model The KNMI Climate Explorer Summary

3 2006 Spring 2m temperature Whereas global warming is a topical issue world wide, there is still a need to investigate the predictability of cold extremes in e.g Europe (spring 2006 a good illustration)

4 Operational GCMs verified MODELRESOLUTIONREFERENCE ECMWF-2T95L40 van Oldenborgh et al. (2005a,b) NCEP-CFST62L64Saha et al. (2005) UKMO3.75° x 2.5° L55Scaife et al. (2000)

5 Model ROC curves

6 Model ROC scores normal seasons All three models show some skill in predicting near- average seasons in Eastern Europe, but……..

7 Models verified against NCEP-NCAR Reanalysis Model ROC scores coldest seasons The skill is even much higher over the same area for the coldest springs…..suggesting that there is some physical mechanism responsible.

8 Data source: NCEP-CPC Monitoring and data Snow Cover Climatology Amongst other candidate land surface processes influencing cold spells in NE Europe is the presence or absence of snow and its effect on the albedo and sensible heat exchange Snow cover climatology expresses the fraction of time with snow on the ground. Interannual standard deviations of the probability of the presence of snow on the ground early in March- April

9 Scatter plots Spatial averaged early February snow water equivalent (mm) versus boreal spring near-surface (2m) temperature. The three coldest MAMs were characterised by high snow-depth on the ground. The effect of snow on the center of the temperature distribution is smaller

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14 Verification of Principal Regression model? Using the regression model the area of highest skill shifts is more southward?

15 The KNMI Climexp (http:climexp.knmi.nl)

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18 Summary There is an obvious incentive for investigating the predictability of cold outbreaks in Europe as demonstrated during last spring. The GCMs verified seem to be predicting these extremes skillfully over Eastern Europe. Snow-related feedbacks are in part responsible for colder spring seasons. More accurate analysis of snow is expected to improve colder temperature predictions. To do....Methods of improving GCM prediction (e.g. statistical recalibration).


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