1. Seasonal Cycle of Climate Feedbacks in the NCAR CCSM3.0 Patrick Taylor CLARREO Science Team Meeting July 7, 2010 Patrick Taylor CLARREO Science Team Meeting July 7, 2010

2. Influence of Feedback Seasonality on CLARREO  We must consider that climate feedbacks may have seasonal structure.  Based on these results, the seasonality of LW global mean climate feedbacks is small. However, the results suggest that LW feedbacks exhibit a seasonal cycle in the zonal mean.  The SW global mean climate feedbacks, however, seems to exhibit seasonal variability in the global mean due to northern and southern hemispheric differences.  We must consider that climate feedbacks may have seasonal structure.  Based on these results, the seasonality of LW global mean climate feedbacks is small. However, the results suggest that LW feedbacks exhibit a seasonal cycle in the zonal mean.  The SW global mean climate feedbacks, however, seems to exhibit seasonal variability in the global mean due to northern and southern hemispheric differences.

3. Why look at the seasonality of climate feedbacks?  Different physics will dominate in different seasons at different regions, thus evaluating model differences in the seasonal feedbacks may suggest difference due to certain parameterizations.  Causes of inter-model differences in feedbacks may be revealed by looking at the geographic and seasonal distribution of feedbacks.  Different physics will dominate in different seasons at different regions, thus evaluating model differences in the seasonal feedbacks may suggest difference due to certain parameterizations.  Causes of inter-model differences in feedbacks may be revealed by looking at the geographic and seasonal distribution of feedbacks.

4. Seasonal Cycle and Climate Sensitivity  How can the seasonal cycle influence the climate sensitivity?  Colman (2003)  Zhang et al. (2005)  Lu and Cai (2010)  2-Box EBM Result  How can the seasonal cycle influence the climate sensitivity?  Colman (2003)  Zhang et al. (2005)  Lu and Cai (2010)  2-Box EBM Result

5. Zhang et al. (2005)

6. Lu and Cai (2009)

7. Model Information  NCAR CCSM3.0  T85 resolution- 1.41  x1.41   Coupled Ocean  SRESA1B IPCC AR4  Approximate doubling of year 2000 CO 2 levels by 2100.  NCAR CCSM3.0  T85 resolution- 1.41  x1.41   Coupled Ocean  SRESA1B IPCC AR4  Approximate doubling of year 2000 CO 2 levels by 2100.

8. Seasonal LW CRE CERES EBAFNCAR CCSM3.0

9. Seasonal SW CRE NCAR CCSM3.0CERES EBAF

10. Feedback Calculations  Partial Radiative Perturbation Technique  Wetherald and Manabe (1988)  Feedback radiative perturbations defined as difference between “initial” and “final” states  “Initial”: 2000-2010  “Final”: 2100-2110  Monthly Mean model output used for radiation calculations  Partial Radiative Perturbation Technique  Wetherald and Manabe (1988)  Feedback radiative perturbations defined as difference between “initial” and “final” states  “Initial”: 2000-2010  “Final”: 2100-2110  Monthly Mean model output used for radiation calculations

11. MCICA Subcolumns } subcolumn Large-scale model Gridbox Stochastically sample gridbox mean cloud frequency Cloud Generator Governing Equations

12. Linearity Test

13. Feedback Uncertainties Soden and Held (2006) w =+1.80  0.18 Wm -2 K -1  =-0.84  0.26 Wm -2 K -1 C =+0.69  0.38 Wm -2 K -1  =+0.26  0.08 Wm -2 K -1

14. Interpreting Seasonal Cycle of Feedbacks Wm-2

15. Results: TOA Radiative Forcing and Perturbations Seasonal Cycle

16. Global Mean: Longwave

17. CCSM3.0 vs. BMRC Colman (2003) Water vapor Lapse Rate Clouds

18. Seasonal Variations: Water Vapor, LW

19. Seasonal Variations: Clouds, LW

20. Global Mean: Shortwave

21. CCSM3.0 vs. BMRC Colman (2003) Water vapor Clouds Albedo

22. Seasonal Variations: Surface Albedo, SW

23. Seasonal Variations: Clouds, SW

24. Seasonal Variations: Clouds, Net

25. Summary  The global-mean seasonal contributions to the LW feedbacks show no seasonal variability.  Differences are exhibited between the global- mean seasonal contributions to the SW feedbacks in the NCAR CCSM3.0 and the results of Colman (2003).  Small differences in surface albedo  Large differences in cloud feedback  Model pattern differences in the zonal mean contributions are small, however large inter- model differences in radiative perturbation magnitudes were found.  Implications for CLARREO.  The global-mean seasonal contributions to the LW feedbacks show no seasonal variability.  Differences are exhibited between the global- mean seasonal contributions to the SW feedbacks in the NCAR CCSM3.0 and the results of Colman (2003).  Small differences in surface albedo  Large differences in cloud feedback  Model pattern differences in the zonal mean contributions are small, however large inter- model differences in radiative perturbation magnitudes were found.  Implications for CLARREO.