Assessing the Water Cycle in Regional Climate Simulation

1. Assessing the Water Cycle in Regional Climate Simulation W. J. Gutowski, Jr. Iowa State University with thanks to: F. Otieno, Z. Pan, R. W. Arritt, E. S. Takle SASAS (September 2001)

2. Outline • 10-yr RCM simulations • Precipitation analysis • Error evaluation • Conclusions: Sources of error? SASAS (September 2001)

3. Simulations

4. Simulations

5. Simulation Domain

6. Observations • Precipitation • VEMAP - monthly; 0.5˚ x 0.5˚ • Higgins et al. - hourly; 2˚ x 2.5˚ • Circulation – NCEP/NCAR reanalysis • Precipitable water – NCEP/NCAR reanalysis • Runoff - UNH 0.5˚ climatology

7. Outline • 10-yr RCM simulations • Precipitation analysis • Error evaluation • Conclusions: Sources of error? SASAS (September 2001)

8. Diagnoses • Bias: average difference • Bias Score: intensity “spectrum” • SOM: pattern difference

9. Precip.Bias by Month & Location -2 0 2 4 [mm/d]

10. Season’s Bias by Year ~ south-central US ~ (“Fall” = Sep-Oct-Nov, etc.)

11. Bias Score by Location Threshold = 1 mm/d (“Score” ~ relative exceeding of threshold)

12. Bias Score by Location Threshold = 2 mm/d (“Score” ~ relative exceeding of threshold)

13. Bias Score by Location Threshold = 4 mm/d (“Score” ~ relative exceeding of threshold)

14. Bias Score by Month ~ south-central US ~ (“Score” ~ relative exceeding of threshold)

15. Self-Organizing Maps • Set of maps • Show characteristic data structures • Trained to distribution of data • Give 2-D projection of higher order • map space • Are approximately continuous

16. SOM: RegCM2 & VEMAP Precipitation

17. SOM: RegCM2 & VEMAP Precipitation 1 2

18. SOM: Major Dimensions 1 “warm” 2 “cold” 0 [mm/mo] 100 200

19. SOM: RegCM2 & VEMAP Precipitation

20. SOM: RegCM2 & VEMAP Precipitation

21. SOM Trajectories RegCM VEMAP J-J-A

22. SOM Trajectories RegCM VEMAP J-J-A RegCM D-J-F VEMAP D-J-F

23. SOM: Major Dimensions 2 “cold” 0 [mm/mo] 100 200

24. Trajectory Separation by Month

25. Outline • 10-yr RCM simulations • Precipitation analysis • Error evaluation • Conclusions: Sources of error? SASAS (September 2001)

26. 500 hPa Heights & Bias Sep-Oct-Nov [m]

27. 500 hPa Bandpass Variance & Bias Sep-Oct-Nov [m2]

28. Precipitable Water & Bias Sep-Oct-Nov [kg-m-2]

29. Simulation Domain

32. Water Balance Analysis From terrestrial balance: Evapotranspiration error Observed runoff Model output Precipitation error

33. Water Balance Analysis From terrestrial balance: Evapotranspiration error Subsurface storage Observed runoff Model output Precipitation error

34. Water Balance Analysis From atmospheric balance: Vapor convergence error Evapotranspiration error Precipitation error

35. Error: Ten-year average

36. Water Balance Analysis For Sep-Oct-Nov:

37. Water Balance Analysis For Sep-Oct-Nov: • Plausible values? • model’s root-zone storage: => -0.5 mm/d • (P-E)m - Ro: => -0.1 mm/d

38. Error: S-O-N average

39. Outline • 10-yr RCM simulations • Precipitation analysis • Error evaluation • Conclusions: Sources of error? SASAS (September 2001)

40. Evapotranspiration error from: • Temperature error? SASAS (September 2001)

41. Daily Max. Temperature RegCM2 Difference VEMAP -12.5 - 2.5 2.5 12.5 22.5 [oC]

42. Daily Min. Temperature RegCM2 Difference VEMAP -12.5 - 2.5 2.5 12.5 22.5 [oC]

43. Evapotranspiration error from: • Temperature error? Apparently no. • Surface moisture error? SASAS (September 2001)

44. The region has substantial wetlands: SASAS (September 2001)

45. The region has substantial wetlands: • Not resolved by 60 km grid. • Large source of water? SASAS (September 2001)

46. Acknowledgments • Primary Funding: U.S. National Oceanic and Atmospheric Administration (NOAA) • Additional Support: Electric Power Research Institute (EPRI) SASAS (September 2001)

47. EXTRA SLIDES

48. RegCM2 Bias VEMAP JAN JUL - 4 -2 0 +2 +4 +6 [mm/d]