assessing the water cycle in regional climate simulation

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


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)

“ “ “

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


OutlineOutline





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


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


1

2

SOM: Major Dimensions

0 [mm/mo] 100 200

“warm”

“cold”

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


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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:


ΔE=ΔP −(P −E)m +Ro +dWdt o

Observed runoff

Model output

Precipitation error


From terrestrial balance:

Subsurface storage


ΔC=ΔP −ΔE

Precipitation 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



For Sep-Oct-Nov:



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


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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]


Evapotranspiration error from:Evapotranspiration error from:

Temperature error? Apparently no.Temperature error? Apparently no.

Surface moisture error?Surface moisture error?


The region has substantial wetlands:The region has substantial wetlands:


Not resolved by Not resolved by

60 km grid.60 km grid.

Large source of Large source of

water?water?


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)


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


……and substantial irrigation:and substantial irrigation:


Hydrological units boundaries:Hydrological units boundaries:

assessing the water cycle in regional climate simulation

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