1. Boulder, June, 2006 Extremes in Ensemble Simulations of the Maunder Minimum: Midlatitude Cyclones, Precipitation, and Wind speed Christoph Raible (1) M. Yoshimori (1,2), T. Stocker (1), C. Casty (1) (1) Climate and Environmental Physics, Physics Institute, University of Bern, Project: NCCR Climate (2) Center for Environmental Prediction, Rutgers University, USA Bern

2. A European Pattern Climatology from 1766-2000 Motivation Coast line of northern Germany Hamburg

3. A European Pattern Climatology from 1766-2000 Outline > Model and experimental design > Mean changes in the Maunder Minimum > Extremes in cyclone intensity > Summary > Outlook

4. A European Pattern Climatology from 1766-2000 Model Community Climate System Model (version 2 from NCAR)  Atmosphere: T31(3.75ºx3.75º), 26 vertical levels  Ocean: 3.6ºx1.8º, 25 vertical levels  Land  Sea ice  Coupled without flux corrections

5. A European Pattern Climatology from 1766-2000 Experimental design Simulations:  1990 control forced with perpetual 1990 AD conditions: 300 yrs (used: last 152yrs)  1640 control forced with perpetual 1640 AD conditions: 350 yrs  6 transient ensemble simulations for the Maunder Minimum (TMM) from 1640 -1715 AD

6. A European Pattern Climatology from 1766-2000 Experimental design Simulations:  1990 control forced with perpetual 1990 AD conditions: 300 yrs (used: last 152yrs)  1640 control forced with perpetual 1640 AD conditions: 350 yrs  6 transient ensemble simulations for the Maunder Minimum (TMM) from 1640 -1715 AD

7. A European Pattern Climatology from 1766-2000 Mean changes: cyclone density (DJF) Difference: mean of TMM – 1990 CTRL 1990 CTRL Unit: number / (1000km) 2 significant at the 5% level

8. A European Pattern Climatology from 1766-2000 Mean changes in extremes (DJF) Difference TMM – 1990 CTRL of the 90% percentile of Precipitation Unit: mm/day significant at the 5% level wind speed Unit: m/s

9. A European Pattern Climatology from 1766-2000 Definition of regions Atlantic Pacific Europe Northern Europe Southern Europe

10. A European Pattern Climatology from 1766-2000 Definition of cyclone intensity Cyclone intensity index Distribution of intensity index Cyclone track: Estimation of Z1000 gradient within 1000km around the minimum for each time step

11. A European Pattern Climatology from 1766-2000 Extremes in cyclone intensity > Ensemble of Maunder Minimum Simulations (TMM) > 1990 Control simulation (CTRL) Distribution of the intensity of strong cyclones in the North Atlantic (DJF):

12. A European Pattern Climatology from 1766-2000 Mean changes in extreme cyclone intensity Significant values (95% level) are highlighted in bold. If all ensemble members have greater values than the control, the means are underlined. Sea.ATLEURN-EURS-EURPAC DJF+1.8+2.7+3.9+2.9+0.2 MAM+0.4+0.5+0.8+1.2+0.4 JJA+1.4+1.5+1.2+0.2+0.5 SON+1.4+0.4+0.2+3.0+1.9 Difference in the mean of the distribution of cyclone intensity (TMM – 1990 Ctrl)

13. A European Pattern Climatology from 1766-2000 Summary  A southward shift of the tail-end of the mid-latitude cyclone tracks in the Maunder Minimum (MM) which is related to extremes in precipitation and wind speed in winter  Extremes in cyclone intensity are stronger in the MM compared with today, even though the number of cyclones is decreased in some areas (e.g., northern Europe).

14. A European Pattern Climatology from 1766-2000 Reason for intensification of Maunder Minimum cyclones —Increased meridional temperature gradient. —Increased lower tropospheric baroclinicity, which is not balanced by the upper tropospheric baroclinicity. —The diabatic component of cyclones seems to play a minor role in intensification of MM cyclones

15. A European Pattern Climatology from 1766-2000 Outlook  Comparison with proxy reconstructions  Analysis of extremes with respect to blocking and cold spell events in the Maunder Minimum  Applying the analysis of extreme to transient simulations with CCSM3 from 1500 to 2100 AD

16. A European Pattern Climatology from 1766-2000 extreme ironing! Worse than extreme cyclones …

17. A European Pattern Climatology from 1766-2000 Mean changes Low-pass filtered Northern Hemisphere temperature anomaly in relation to perpetual 1640 AD simulation: Solar and volcanic forcing:

18. A European Pattern Climatology from 1766-2000 Conclusions  There is a connection between cyclone intensity and precipitation and wind speed extremes in winter.  The cyclone intensity is also connected with the large-scale atmospheric circulation.  In summer the relationships vanish.  Both connections are independent from the climate state (no changes comparing TMM with 1990 Ctrl).

19. A European Pattern Climatology from 1766-2000 Mean changes: 2m temperature (DJF) Difference: mean of TMM – 1990 CTRL 1990 CTRL Unit: Celsius significant at the 5% level

20. A European Pattern Climatology from 1766-2000 Mean changes: Z1000 (DJF) Difference: mean of TMM – 1990 CTRL 1990 CTRL Unit: gpm significant at the 5% level

21. A European Pattern Climatology from 1766-2000 Mean changes: Eady growth rate (DJF) in 700 hPa Difference: mean of TMM – 1990 CTRL 1990 CTRL Unit: 1/day significant at the 5% level

22. A European Pattern Climatology from 1766-2000 Difference: mean of TMM – 1990 CTRL 1990 CTRL Unit: 1/day significant at the 5% level Mean changes: Eady growth rate (DJF) in 300 hPa

23. A European Pattern Climatology from 1766-2000 Conclusions Latent heat flux change TMM – CTRL in W/m 2 for winter

24. A European Pattern Climatology from 1766-2000 Changes in extreme precipitation (90% percentile Difference: mean of TMM – 1990 CTRL DJF Unit: mm/day Shading: 95% significant JJA

25. A European Pattern Climatology from 1766-2000 Changes in extreme precipitation (90% percentile Unit: m/s Shading: 95% significant Difference: mean of TMM – 1990 CTRL DJF JJA

26. A European Pattern Climatology from 1766-2000 Experimental design Simulations:  1990 control forced with perpetual 1990 AD conditions: 300 yrs (used: last 152yrs)  1640 control forced with perpetual 1640 AD conditions: 350 yrs  6 transient ensemble simulations for the Maunder Minimum (TMM) from 1640 -1715 AD

27. A European Pattern Climatology from 1766-2000 Mean changes: precipitation (DJF) Difference: mean of TMM – 1990 CTRL 1990 CTRL Unit: mm/day Shading: 95% significant c

28. A European Pattern Climatology from 1766-2000 Mean changes: wind speed (DJF) in 1000 hPa Difference: mean of TMM – 1990 CTRL 1990 CTRL Unit: m/s Shading: 95% significant

29. A European Pattern Climatology from 1766-2000 Motivation  Have extremes in cyclone characteristics changed under colder climate conditions than today?  Are extremes in cyclone characteristics linked to extremes in precipitation and wind speed?  What is the relation between extremes in cyclones and the general atmospheric circulation?

30. A European Pattern Climatology from 1766-2000  Have extremes in cyclone characteristics changed under colder climate conditions than today?  Are extremes in cyclone characteristics linked to extremes in precipitation and wind speed?  What is the relation between extremes in cyclones and the general atmospheric circulation? Note that half-daily data is used for the following analysis.

31. A European Pattern Climatology from 1766-2000  Have extremes in cyclone characteristics changed under colder climate conditions than today?  Are extremes in cyclone characteristics linked to extremes in precipitation and wind speed?  What is the relation between extremes in cyclones and the general atmospheric circulation?

32. A European Pattern Climatology from 1766-2000 Correlation: Cyclone intensity and extremes in precipitation / wind speed (DJF) Precip.: Wind speed: Atlantic N-Europe S-Europe c

33. A European Pattern Climatology from 1766-2000 Correlation: Cyclone intensity and extremes in precipitation / wind speed (JJA) Precip.: Wind speed: Atlantic N-Europe S-Europe

34. A European Pattern Climatology from 1766-2000 Correlation: Cyclone intensity index and Z1000 / 2m temperature (DJF) Z1000: 2m Temp.: Atlantic N-Europe S-Europe

35. A European Pattern Climatology from 1766-2000 Atlantic N-Europe S-Europe Correlation: Cyclone intensity index and Z1000 / 2m temperature (JJA) Z1000: 2m Temp.: