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 Circulation – NCEP/NCAR reanalysis
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
[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 Precipitation1 2

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

19. SOM: RegCM2 & VEMAP Precipitation

20. SOM: RegCM2 & VEMAP Precipitation

21. SOM Trajectories RegCM VEMAP
J-J-A

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

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

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
[oC]

42. Daily Min. Temperature RegCM2 Difference VEMAP
[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 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 +2 +4 +6
[mm/d]

53. SOM Trajectories
RegCM
VEMAP
J-J-A

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

55. 500 hPa Bandpass Variance & Bias
Sep-Oct-Nov
Dec-Jan-Feb
[m2]

56. 500 hPa Bandpass Variance & Bias
Sep-Oct-Nov
[m2]

57. 500 hPa SOM-weighted ave. & bias
October
[m]

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

59. …and substantial irrigation:
SASAS (September 2001)

60. Hydrological units boundaries:
SASAS (September 2001)

61. Hydrological units boundaries: