Lee Titus; BSc (physics), Dmet, MSc Candidate (physics) Environment Canada

1. Statistical Downscaling of General Circulation Models to Produce Climate Change Scenarios for Halifax, NS Lee Titus; BSc (physics), Dmet, MSc Candidate (physics) Environment Canada Meteorological Service of Canada Climate Change Section In collaboration with Dr. Richard Greatbatch, Dr. Jinyu Sheng and Dr. Ian Folkins in the Department of Atmospheric Science at Dalhousie University 1

3. Typical grid spacing in a GCM

4. 4 From IPCC 2001

5. METHOD • Remove seasonal cycle from predictand/predictors. • Focus on Winter (DJF) • Predictor Selection • Principal component analysis (PCA). • Multiple linear regression on Tmax and NCEP PC’s. • Validation • Use CGCM3 predictors to hindcast historical distribution. • Use future CGCM3 predictors to make projections.

6. Seasonal cycle removal

7. Predictor Selection mean sea level Pressure *** Redundancy inspired the removal of 500hpa geopotential height 500hpa zonal windspeed. 500hpa meridional windspeed total windspeed 500hpa vorticity 850hpa geopotential height 850hpa zonal windspeed 850hpa meridional windspeed wind direction 850hpa vorticity surface zonal windspeed surface meridional windspeed surface vorticity divergence 500hpa specific humidity 850hpa specific humidity surface specific humidity surface mean temperature

8. PCA/MLR BASICS

9. PCA mean sea level pressure -0.17 500hpa geopotential height 0.14 500hpa zonal windspeed -0.05 500hpa meridional windspeed 0.48 500hpa vorticity -0.14 ***CORRELATION = 0.62 850hpa geopotential height -0.0140% of the variation in TMAX is 850hpa zonal windspeed -0.08explained by temperature advection 850hpa meridional windspeed 0.58 850hpa vorticity 0.10 surface zonal windspeed -0.13 surface meridional windspeed 0.52 surface vorticity 0.24

10. PCA 850GPH 500GPH ???? MSLP

11. REGRESSION INFO Explained variance (percent) 79 Regression error variance 0.07 Number of predictors (PC's) 10 Gamma squared 0.21

12. VALIDATION

13. NCEP PREDICTION

14. NEXT • Once the best historical model from NCEP has been made…hindcast using CGCM3 predictors. • Project the CGCM3 predictors onto the eigenvectors created from NCEP.

15. CGCM3 PREDICTION

16. PROJECTIONS 1

17. SUMMARY • Predictor Selection/PCA improves regression • Reduces autocorrelation of regression errors (removal of seasonal cycle). • Identify governing physics by season (gives confidence in the future). • Normal distributions are a much better assumption using seasons compared to annual.

18. My Next Steps • FDEOFR to get regression coefficients as a function of frequency. • FDEOFR gives candidate downscaling frequencies and helps sort out physics (climate vs. weather)

19. CLIMATE QUOTES “The reasonable man tries to adapt to the world around him, while the unreasonable tries to adapt the world to himself. Therefore all progress depends on the unreasonable man” --George Bernard Shaw “The real problem is not global warming. It is in fact the majority’s level of awareness. As if we are somehow separate from nature” --Lee Titus “The laws of Congress and the laws of physics have grown increasingly divergent, and the laws of physics are not likely to change."--Bill McKibben