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)

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

Simulations

Simulations

Simulation Domain

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

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

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

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

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

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

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

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

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

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

SOM: RegCM2 & VEMAP Precipitation

SOM: RegCM2 & VEMAP Precipitation 1 2

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

SOM: RegCM2 & VEMAP Precipitation

SOM: RegCM2 & VEMAP Precipitation

SOM Trajectories RegCM VEMAP J-J-A

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

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

Trajectory Separation by Month

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

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

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

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

Simulation Domain

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

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

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

Error: Ten-year average

Water Balance Analysis For Sep-Oct-Nov:

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

Error: S-O-N average

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

Evapotranspiration error from: Temperature error? SASAS (September 2001)

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

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

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

The region has substantial wetlands: SASAS (September 2001)

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

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

EXTRA SLIDES

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

SOM Trajectories RegCM VEMAP J-J-A

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

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

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

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

The region has substantial wetlands: SASAS (September 2001)

…and substantial irrigation: SASAS (September 2001)

Hydrological units boundaries: SASAS (September 2001)

Hydrological units boundaries: