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September 17th 2003 - ICID RS ET - Montpellier 1
On SEBI-SEBS validation in France, Italy, Spain, USA and China
Massimo Menenti Li Jia2 and ZongBo Su2
- Laboratoire des Sciences de l ’Image, de l ’Informatique et de la Télédétection (LSIIT) , Strasbourg, France
-Istituto per i Sistemi Agricoli e Forestali del Mediterraneo (ISAFoM), National Research Council (CNR), Italy2ALTERRA Green World Research, Wageningen University and Research Centre, 6700 AA Wageningen, The Netherlands;
September 17th 2003 - ICID RS ET - Montpellier 2
land evaporation: processes and observations
potential
heat balancesurface
water balancesoil
water balanceair
actual
evaporationland
0=+++ LEHGRn PEqdivtv
v −=+δδ0=+++++ EwmQIP δδ
September 17th 2003 - ICID RS ET - Montpellier 3
Actual evaporation:a history of methods
NDVI vs. Trad[3]
linear relationshipB, n variable
[2]
linear relationship[1]
SVAT+
PBL[5]
SVAT[4]
improvedobservations
[7]
local maximum ET[6]
heat balanceland surface
Menenti, 2001
September 17th 2003 - ICID RS ET - Montpellier 4
RS flux-algorithms
• SEBAL (Bastiaanssen, 1995)
• SEBI (Menenti & Choudhury, 1993; • Su et al, 2000)
• Dual - view angle measurements of surface temperature (Menenti et al, 2001)
temperature
albe
do
LE ≈ 0
H ≈ 0
pbl-temp
obs
September 17th 2003 - ICID RS ET - Montpellier 5
SEBI: theory and definitions
)r()T-T(-
)r()T-T(
)r()T-T(-
r)T-T(
SEBI
we
wa0
de
da0
we
wa0
e
a0
=SEBI-1=
EEwet
r λλ=Λ
GRE
n −λ=Λ
( )( )GRH n −Λ−= 1
��
���
����
�
�−���
�
�=
∆
max0hmax
*pamax Cln1Lh
zh
κHucρθ
��
���
����
�
�−���
�
�=
∆
minh0min
*pamin Clnκ1
Lh
zh
Hucρθ
Menenti and Choudhury (1993)
Hmin : ( ) ( )γ+
−+−=
seercρGQs
λE satapa*wet
/GQH −= *max
Reference height = PBL top or blending height
Ta = potential air temperature
September 17th 2003 - ICID RS ET - Montpellier 6
Case studies
• France, DAISEX 1999 at Colmar and Hartheim (Jia et al., 2001)• Italy, Pian di Rosia 1997 (Roerink et al., 2000).• Spain (Jia et al., 2003)• USA SGP ’97 (Su et al., 2002)• China (Su et al., 2003)
September 17th 2003 - ICID RS ET - Montpellier 7
DAISEXL Overview of data collected
- DAIS (Digital Airborne Imaging Spectrometer)- HYMAP (Hyperspectral Mapper)- ROSIS (Reflective Optics System Imaging Spectrometer)- POLDER (POLarized and Directional Earth's Reflectances)
-WAAC (Wide Angle Airborne Camera)
- LEANDRE LIDAR (aerosols lidar)- ARAT (in-situ atmospheric sensors)
- ERS-1/ERS-2 Tandem SAR
- Landsat TM / SPOT data (for the dates of campaigns)
THREE YEARS OF CAMPAIGNS:Barrax: 1998, 1999 and 2000; Alsace: 1999
September 17th 2003 - ICID RS ET - Montpellier 8
SEBI from field measurements
-0.4
-0.2
0
0.2
0.4
0.6
0.17 0.18 0.19 0.2 0.21 0.22
albedo
Nor
mor
lized
(T0
- Ta)
(K /
(s m
-1))
Wet conditionActualDry condition
-100
0
100
200
300
400
500
600
09:00 09:20 09:32 09:40 12:00 12:20 12:48 16:14 17:00
Hour(UTC)
Ener
gy fl
ux (
W m
-2)
Rn G H_obsH_sebi LE_obs LE_sebi
SEBI Flux densities
200
250
300
350
200 250 300 350
LE obsevation ( W m-2 )
LE e
stim
atio
n by
SE
BI (
W m
-2 )
RMSD = 17.4 W m-2
Colmar, sugar beet: SEBI estimates vs. field measurements
RMSD = 17.4 Wm-2
September 17th 2003 - ICID RS ET - Montpellier 9
Dry and Wet reference vs. Observations
September 17th 2003 - ICID RS ET - Montpellier 10
From SEBI to LE - map
-0.4
-0.2
0
0.2
0.4
0.6
0.8
0 0.05 0.1 0.15 0.2 0.25
albedo
Nor
mal
ized
(T0-
Ta) (
K/(s
m-1
) )
Wet boundaryActualDry boundary
Colmar sugarbeet
Fallow
Sugar beet
Bare soil
maizDistribution of LE at Colmar sub-site; cross indicates location of field measurements
normalized (T0 – Ta) versus surface albedo; airborne HYMAP, DAIS, Colmar
Wm-2
LE
September 17th 2003 - ICID RS ET - Montpellier 11
The Simplified Surface Energy Balance Index ( SEBI )
10
20
30
40
50
60
0 0.2 0.4 0.6 0.8 1
Surface reflectance (-)
Sur
face
tem
pera
ture
(o C)
mean temperature
T H
λE max (r 0)
H max (r 0)
T 0
T λE
0
50
100
150
200
250
0 50 100 150 200 250
H [S-SEBI] (W/m2)H
[me
asu
red
] (W
/m2
)
eddy correlationbowen ratioscintillometer
Menenti and Choudhury, 1993; Roerink et al., 1999
September 17th 2003 - ICID RS ET - Montpellier 12
SEBS Core Modules
Boundary Layer Similarity Theory
Roughness for Heat Transfer
Surface Energy Balance Index
Meteorological Data
Boundary Layer Variables
Remote Sensing Data
VIS
NIR TIR
Input Output
EvaporativeFraction
Turbulence Heat Fluxes
Actual Evaporation
SEBS - The Surface Energy Balance System
September 17th 2003 - ICID RS ET - Montpellier 13
Spain: validation with scintillometers
Location of scintillometer measurements sites
Transmitter Receiver Surface Site Location Height
(m) Location Height
(m)
Distance between transmitter and
receiver (m) Characteristics
Tomelloso 39°07.357′N
2°55.314′W
4.56 39°07.653′N
2°55.951′W
4.15 1070 Dry vineyard
Lleida 41°32.644′N
0°51.644′E
39 41°34.962′N
0°52.444′E
45 4440 Small scale irrigation area with fruit trees, alfalfa
Badajoz 38°55.697′N
6°36.590′W
68 38°56.298′N
6°40.141′W
56 5250 Large scale irrigation area with wheat, corn, alfalfa, lettuce, olives, beans, tomatoes.
Location and characteristics of scintillometer experimental sites in Spain.
September 17th 2003 - ICID RS ET - Montpellier 14
SEBS Data RequirementsSurface temperature (K) ATSR
Surface albedo (–) ATSR
NDVI (–) ATSR
Fractional vegetation cover (–) ATSR
PBL depth (m) NWP-RACMO
PBL pressure (Pa) RACMO
PBL potential temperature (K) RACMO
PBL speci.c humidity (%) RACMO
PBL wind speed (m/s) RACMOChannel Central wavelength 50% band wid
(mm) (mm)1 * 12.0 11.60-12.502 * 11.0 10.52-11.333 3.7 3.47-3.904 1.6 1.575-1.6425 * 0.87 0.853-0.8756 * 0.65 0.647-0.6697 0.55 0.543-0.565 ATSR channels
September 17th 2003 - ICID RS ET - Montpellier 15
Sensible heat flux: SEBI vs. scintillometers
100 150 200 250 300 350
100
150
200
250
300
350
H e
stim
ated
by
SEBS
(W m
-2)
H observed by LAS (W m-2)
Tomelloso Lleida Badajoz
SEBI (SEBS version)
ATSR-2: surface temperature, albedoand NDVI
vertical error bars = standard deviation over pixels along path
horizontal error bars = error LAS measurements
September 17th 2003 - ICID RS ET - Montpellier 16
SEBI: Forward and nadir T0
(Nadir View) (Forward View)
USA: Southern Great Plain 1997 Hydrology Experiment (SGP’97)
Colour from red to yellow, green, blue indicates increasing evaporative fraction
forward view = higher fraction of foliage, lower surface brightness temperature
higher estimate of evaporative fraction
September 17th 2003 - ICID RS ET - Montpellier 17
July 1, 2000July 1, 2000 July 8, 2000July 8, 2000
China: Monitoring Droughts
September 17th 2003 - ICID RS ET - Montpellier 18
April 2000
01020304050607080
0 20 40 60
Relative Evaporation (%)
Aver
age
Rel
ativ
e So
il Moi
stur
e up
to d
epth
of 5
0cm
(%) Average
Relative SoilMoisture upto Depth of50 cmPredictedAverageRelative SoilMoisture
6
April 2000
01020304050607080
0 10 20 30 40 50
Relative Evaporation (%)
Ave
rgae
Rel
ativ
e So
il Moi
stur
e up
to 2
0 cm
Dep
th (%
) AverageRelative SoilMoisture upto Depth of20 cmPredictedAverageRelative SoilMoisture
April 2000
01020304050607080
0 10 20 30 40 50
Relative Evaporation (%)
Rela
tive
Soil M
oist
ure
(at1
0 cm
dep
th)
SOILMOISTURE(at10 cmdepth)PredictedAverageRelative SoilMoisture
China: Relative evaporation vs relative soil moisture
Time Series of Drought Severity Index
Comparison with Soil Moisture Measurements
September 17th 2003 - ICID RS ET - Montpellier 19
Development – related changes in land cover and
water balanceColour composite of multitemporal images of the Soil Adjusted Vegetation Index (SAVI) calculated with AVHRR Ch1 and Ch2 reflectance at 1 km spatial resolution, Aral Sea Basin 1992: SAVI (April)= red; SAVI (june)= green; SAVI (august)= blue; area is 1568 km x 1232 km; greenish areas = irrigated lands
September 17th 2003 - ICID RS ET - Montpellier 20
Concluding Remarks
• Method performs well under different conditions• Use of NWP models to determine PBL variables makes
large area applications feasible• Error budgets give significantly higher error estimates• SEBS will be further developed by integrating generic
algorithms to process TOA radiometric data• Case studies should be expanded to time series