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Testing Remotely Sensed Evapotranspiration Estimates Using Airborne and Ground
Measurements
May 2004
Cressida Savige, Andrew French, Andrew Western, Jeffrey Walker, Mohammad Abuzar, Jorg Hacker and
Jetse Kalma
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Land Surface
Satellite
Satellite Image
Aircraft
LELE
MODEL
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Surface Energy Balance Rn = H + LE + G
RnC
LEC
HS
RnS
LES
HC
G
2-SOURCE
G
H
Rn
LE
1-SOURCE
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Irrigation Region
0 50Km
25
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Airborne Flux Measurements
SENSIBLE HEAT FLUX
0
100
200
300
400
500
600
332500 333500 334500 335500 336500 337500
Easting
En
erg
y F
lux
De
ns
ity
(W
m-2
)
x 10 flights
wi = 109 Wm-2
btw = 43 Wm-2
NR ~ 1
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LELATENT HEAT FLUX
0
50
100
150
200
250
300
332500 333500 334500 335500 336500 337500 338500
Easting
En
erg
y F
lux
De
ns
ity
(W
m-2
)
2-SOURCE = 183 Wm-2
SEBAL = 182 Wm-2
AIRBORNE = 136 Wm-2
H SENSIBLE HEAT FLUX
0
50
100
150
200
250
300
332500 333500 334500 335500 336500 337500 338500
Easting
En
erg
y F
lux
De
ns
ity
(W
m-2
)
SEBAL = 220 Wm-2
2-SOURCE = 217 Wm-2
AIRBORNE = 157 Wm-2
B = 1.2
AIRBORNE
B = 1.2
2-SOURCE
B = 1.2
SEBAL
LATENT HEAT FLUX (Wm-2)
0
50
100
150
200
250
300
0 50 100 150 200 250 300
Observed
Mo
de
lled
2-SOURCE
SEBAL
SENSIBLE HEAT FLUX (Wm-2)
0
50
100
150
200
250
300
0 50 100 150 200 250 300
Observed
Mo
de
lled
2-SOURCE
SEBAL
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Regional Fluxes
0 5Km
2.5
0
50
100
150
200
250
300
H LE
En
erg
y F
lux
De
ns
ity
(W
m-2
)
2-SOURCE
2-SOURCE
SEBAL
SEBAL
AIRBORNE
AIRBORNE
B = 3.2
AIRBORNE
B = 2.8
2-SOURCE
B = 1.7
SEBAL
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Model ComparisonDifference = 2-SOURCE - SEBAL
Sensible Heat Flux Difference Latent Heat Flux Difference
-160 1600 Wm-2
0 5Km
2.5 0 5Km
2.5
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Findings…
• Model estimates are
• Scale of surface heterogeneity is important…
• Model agreement…Pasture: good
Sparse cover: poor
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This project was supported by:
• Australian Research Council
• University of Melbourne
• Hydrological Sciences Branch, NASA Goddard Space Flight Centre
& Nanneella LandCare Group