Assessing the Water Cycle in Regional Climate Simulation
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Assessing the Water Cycle Assessing the Water Cycle in in
Regional Climate SimulationRegional Climate Simulation
W. J. Gutowski, Jr.W. J. Gutowski, Jr.Iowa State UniversityIowa State University
SASAS (September 2001)
with thanks to: with thanks to: F. OtienoF. Otieno, Z. Pan, R. W. Arritt, E. S. Takle, Z. Pan, R. W. Arritt, E. S. Takle
SASAS (September 2001)
OutlineOutline
10-yr RCM simulations10-yr RCM simulations
Precipitation analysisPrecipitation analysis
Error evaluationError evaluation
Conclusions: Sources of error?Conclusions: Sources of error?
Simulations
Model Observed GCM-control GCM-Scenario
RegCM2 NCEPReanalysis(1979-1988)
HadleyCentre(~1990’s)
HadleyCentre(2040-2050)
HIRHAM(DMI)
“ “ “
Simulations
Model Observed GCM-control GCM-Scenario
RegCM2 NCEPReanalysis(1979-1988)
HadleyCentre(~1990’s)
HadleyCentre(2040-2050)
HIRHAM(DMI)
“ “ “
Simulation DomainSimulation Domain
PrecipitationPrecipitation
– VEMAP - monthly; 0.5˚ x 0.5˚VEMAP - monthly; 0.5˚ x 0.5˚
– Higgins et al. - hourly; 2˚ x 2.5˚Higgins et al. - hourly; 2˚ x 2.5˚
Circulation – NCEP/NCAR reanalysisCirculation – NCEP/NCAR reanalysis
Precipitable water – NCEP/NCAR reanalysisPrecipitable water – NCEP/NCAR reanalysis
Runoff - UNH 0.5˚ climatologyRunoff - UNH 0.5˚ climatology
Observations
SASAS (September 2001)
OutlineOutline
10-yr RCM simulations10-yr RCM simulations
Precipitation analysisPrecipitation analysis
Error evaluationError evaluation
Conclusions: Sources of error?Conclusions: Sources of error?
Bias: average differenceBias: average difference
Bias Score: intensity “spectrum”Bias Score: intensity “spectrum”
SOM: SOM: pattern differencepattern difference
Diagnoses
Precip.Bias by Month & Location
-2 0 2 4 [mm/d]
-40
0
1979 1981 1983 1985 1987Year
WINTER SPRING
SUMMER FALL
Season’s Bias by Year~ south-central US ~
(“Fall” = Sep-Oct-Nov, etc.)
(“Score” ~ relative exceeding of threshold)
Bias Score by LocationThreshold = 1 mm/d
(“Score” ~ relative exceeding of threshold)
Bias Score by LocationThreshold = 2 mm/d
(“Score” ~ relative exceeding of threshold)
Bias Score by LocationThreshold = 4 mm/d
(“Score” ~ relative exceeding of threshold)
Bias Score by Month~ south-central US ~
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
1
2
SOM: RegCM2 & VEMAP Precipitation
1
2
SOM: Major Dimensions
0 [mm/mo] 100 200
“warm”
“cold”
SOM: RegCM2 & VEMAP Precipitation
SOM: RegCM2 & VEMAP Precipitation
SOM Trajectories
RegCM
VEMAP
J-J-A
SOM Trajectories
RegCM
D-J-F
VEMAP
D-J-F
RegCM
VEMAP
J-J-A
2
SOM: Major Dimensions
0 [mm/mo] 100 200
“cold”
Trajectory Separation by Month
SASAS (September 2001)
OutlineOutline
10-yr RCM simulations10-yr RCM simulations
Precipitation analysisPrecipitation analysis
Error evaluationError evaluation
Conclusions: Sources of error?Conclusions: Sources of error?
500 hPa Heights & BiasSep-Oct-Nov
[m]
[m2]
500 hPa Bandpass Variance & Bias
Sep-Oct-Nov
[kg-m-2]
Precipitable Water & Bias
Sep-Oct-Nov
Simulation DomainSimulation Domain
Sep-Oct-Nov 1984
-25
0
25
50
1 31 61 91Time (days)
RegCM2Higgins
Sep-Oct-Nov 1987
-25
0
25
50
1 31 61 91Time [days]
RegCM2
Higgins
Water Balance AnalysisWater Balance Analysis
ΔE =ΔP −(P −E)m +Ro
Observed runoff
Model output
Precipitation error
Evapotranspiration error
From terrestrial balance:
Water Balance AnalysisWater Balance Analysis
ΔE=ΔP −(P −E)m +Ro +dWdt o
Observed runoff
Model output
Precipitation error
Evapotranspiration error
From terrestrial balance:
Subsurface storage
Water Balance AnalysisWater Balance Analysis
ΔC=ΔP −ΔE
Precipitation error
Evapotranspiration error
From atmospheric balance:
Vapor convergence error
Error: Ten-year averageError: Ten-year average
-1.5
-1
-0.5
0
B C DΔ ΔΔP E C
Water Balance AnalysisWater Balance Analysis
ΔE=ΔP −(P −E)m +Ro +dWdt o
For Sep-Oct-Nov:
Water Balance AnalysisWater Balance Analysis
ΔE=ΔP −(P −E)m +Ro +dWdt o
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 averageError: S-O-N average
-3
-2
-1
0
1
-1 -0.5 0 0.5 1
P E C
Storage [mm/d]
Δ ΔΔP E C
SASAS (September 2001)
OutlineOutline
10-yr RCM simulations10-yr RCM simulations
Precipitation analysisPrecipitation analysis
Error evaluationError evaluation
Conclusions: Sources of error?Conclusions: Sources of error?
SASAS (September 2001)
Evapotranspiration error from:Evapotranspiration error from:
Temperature error?Temperature error?
Daily Max. TemperatureRegCM2 Difference VEMAP
-12.5 - 2.5 2.5 12.5 22.5 [oC]
Daily Min. TemperatureRegCM2 Difference VEMAP
-12.5 - 2.5 2.5 12.5 22.5 [oC]
SASAS (September 2001)
Evapotranspiration error from:Evapotranspiration error from:
Temperature error? Apparently no.Temperature error? Apparently no.
Surface moisture error?Surface moisture error?
SASAS (September 2001)
The region has substantial wetlands:The region has substantial wetlands:
SASAS (September 2001)
Not resolved by Not resolved by
60 km grid.60 km grid.
Large source of Large source of
water?water?
The region has substantial wetlands:The region has substantial wetlands:
AcknowledgmentsAcknowledgments
Primary Funding: Primary Funding: U.S. National Oceanic and Atmospheric U.S. National Oceanic and Atmospheric
Administration (NOAA)Administration (NOAA)
Additional Support: Additional Support: Electric Power Research Institute (EPRI)Electric Power Research Institute (EPRI)
SASAS (September 2001)
EXTRA
SLIDES
RegCM2 Bias VEMAP
JAN
JUL
0-2 +2 [mm/d]+4 +6- 4
SOM TrajectoriesRegCM
VEMAP
J-J-A
SOM Trajectories
RegCM
D-J-F
VEMAP
D-J-F
RegCM
VEMAP
J-J-A
500 hPa Bandpass Variance &
Bias
(a) Sep-Oct-Nov
(b) Dec-Jan-Feb
[m2]
[m2]
500 hPa Bandpass Variance & Bias
Sep-Oct-Nov
[m]
500 hPa SOM-weighted ave. & bias
October
SASAS (September 2001)
The region has substantial wetlands:The region has substantial wetlands:
SASAS (September 2001)
……and substantial irrigation:and substantial irrigation:
SASAS (September 2001)
Hydrological units boundaries:Hydrological units boundaries:
Hydrological units boundaries:Hydrological units boundaries:
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