1. Evapotranspiration monitoring: an overview
Gellens-Meulenberghs F., Arboleda, A. and Ghilain, N.
Royal Meteorological Institute,
Avenue Circulaire, 3,
B-1180 Brussels, Belgium

2. 8th APMG Symposium/3rd SALGEE Workshop 2013
Content
Introduction
Methodology
Validation
Products and examples
To get information
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8th APMG Symposium/3rd SALGEE Workshop 2013

3. 8th APMG Symposium/3rd SALGEE Workshop 2013
Introduction
The water cycle
From (
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8th APMG Symposium/3rd SALGEE Workshop 2013

4. 8th APMG Symposium/3rd SALGEE Workshop 2013
Introduction
From (
transpiration
evaporation
evapotranspiration
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8th APMG Symposium/3rd SALGEE Workshop 2013

5. Large differences depending on places and seasons
Introduction
Water and energy budget (monthly values at global scale)
Latent heat flux, associated to evapotranpiration, consumes a large part of available energy
Deep percolation
28 %
Surface runoff
14 %
Total precipitation
100 %
Ground surface
Evapotranspiration
58 %
Net radiation
100 %
Ground surface
Latent heat
53 %
Sensible heat
45 %
Ground heat
2 %
Large differences depending on places and seasons
Evapotranpiration consumes a large part of precipitation
From Dirmeyer, 2011 (J. Hydrometeorol., 12, )
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8th APMG Symposium/3rd SALGEE Workshop 2013

6. 8th APMG Symposium/3rd SALGEE Workshop 2013
Introduction
Multimodels show a lot of uncertainty
Previous intercomparisons have highlighted large differences in modelled and satellite-based heat flux products that exist for particular regions and periods (Jimenez et al., 2011).
Our objective: to improve ET assessment thanks to MSG SEVIRI data
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7. 8th APMG Symposium/3rd SALGEE Workshop 2013
Methodology
Bare soil
Grass
High vegetation
The tile approach: The energy exchanges between the surface and the atmosphere is modelled using a resistance scheme. Each pixel in the image is divided into ‘tiles’ of homogeneous vegetation types
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8. 8th APMG Symposium/3rd SALGEE Workshop 2013
Methodology
Pixels and tiles:
MSG pixel
Tiles:
% of bare soil
% of forest
% of crops
% of grassland …
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9. Methodology Where: Sensible heat flux (Hi) Latent heat flux (LEi)
Energy balance at the skin layer :
Where:
……………………………….…….…….…… (1) S
= DSSFSAF
………………………………………(2)
 = ALSAF L
= DSLFSAF
….….. (3)
Sensible heat flux (Hi)
 = emissivity
………………………………..… (4)
Tsk,i = skin temperature
Ta = air temperature
Latent heat flux (LEi)
= air density
……….…………………….... (5)
air humidity
aerodinamic resisstance
Ground heat flux (Gi)
canopy resisstance
……………………………………………………... (6)
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8th APMG Symposium/3rd SALGEE Workshop 2013

10. Methodology Canopy resistance rci Aerodynamic resistance
Maximum transpiration rate (plant species dependent)
Canopy resistance rci
Total surface leaves (scaling leaf properties to landscape)
Empirical functions (plant response to ambiant factors)
Aerodynamic resistance
Heat fluxes at pixel level dr
d h z0
Turbulence generation by wind
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11. 8th APMG Symposium/3rd SALGEE Workshop 2013
Methodology
Daily evapotranspiration product (DMET): temporal integration of instantaneous (METi) product.
METi : instantaneous evapotranspiration for i time-step between 00:30 UTC and 24:00 UTC.
In optimal conditions (no missing slots) 48 images are integrated for a given day.
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8th APMG Symposium/3rd SALGEE Workshop 2013

12. * -To be included in future versions
Methodology
from satellite MSG-II
FVC -Fractional Vegetation Cover-
LST -Land Surface Temperature-
LAI -Leaf Area Index-
AL -Surface ALbedo-
DSSF-Shortwave flux at surface
DSLF-Longwave flux at surface *
MODEL
FORMULATION
Ti -Tiles in pixel-
FVi -Fraction of tiles-
Rsi -Tile minimum stomatal resistance
LAIi -Tile Leaf Area Index -
FVCi -Tile fractional vegetation cover
ALM -Monthly pixel Albedo
From database (ECOCLIMAP)
MET QF
From NWP (ECMWF)
Ta -Air temperature-
U -Wind speed-
Pa -Air pressure -
Td -Dew-point temperature-
ST -Soil Temperature-
SM -Soil Moisture-
* -To be included in future versions
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13. 8th APMG Symposium/3rd SALGEE Workshop 2013
Methodology
Evapotranspiration (ET): methodology
LSA-SAF data
MET AL
DSSF
DSLF
FVC
LAI
LST
eg. 12th September 2011, 12 UTC.
Ghilain, N., Arboleda, A., Sepulcre-Cantò, G., Batelaan, O., Ardö, J. and Gellens-Meulenberghs, F. (2012) in HESS.
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14. 8th APMG Symposium/3rd SALGEE Workshop 2013
Validation
Spatial scale
From wikipedia
For water flux: s= air humidity
Eddy covariance
FLUXNET network
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15. 8th APMG Symposium/3rd SALGEE Workshop 2013
Validation
Evapotranspiration (ET): validation
MET
fluxes
temperature (for consistency with LST): to be investigated in details during CDOP2
Δ: LSA-SAF DSSF
: obs DSSF
+: LSA-SAF LE
: obs LE
+: LSA-SAF t skin
(internal product, from ET model)
: obs rad temp
+: LSA-SAF LST
: obs air temp
Diepenbeek station, BE
July, 2007
April, 2007
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16. 8th APMG Symposium/3rd SALGEE Workshop 2013
Validation
Evapotranspiration (ET): validation
MET
Cabauw (NL) - grassland
Wetzstein (GE) - coniferous forest
March – Nov
2007
Tojal (PT) - grassland
Vielsalm (BE) - mixed forest
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17. 8th APMG Symposium/3rd SALGEE Workshop 2013
Validation
Evapotranspiration (ET): validation
DMET
Cabauw (NL) - grassland
Wetzstein (GE) - coniferous forest
March – Nov
2007
Tojal (PT) - grassland
Vielsalm (BE) - mixed forest
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18. Instantaneous product (MET, available each 30 min)
Products and examples
Instantaneous product (MET, available each 30 min)
MET
LSA-SAF instantaneous evapotranspiration product (MET)
associated quality flag
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8th APMG Symposium/3rd SALGEE Workshop 2013

19. 8th APMG Symposium/3rd SALGEE Workshop 2013
Products and examples
Instantaneous product (MET, available each 30 min)
24 successive hours (mm h-1):
1 to 6 UTC
7 to 12 UTC
13 to 18 UTC
19 to 24 UTC
28th April 2010
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20. 8th APMG Symposium/3rd SALGEE Workshop 2013
Products and examples
Daily MET product (DMET)
10 successive days (mm d-1):
6th to 10th
11th to 15th
September 2009
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Products and examples
MET in March 2013
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8th APMG Symposium/3rd SALGEE Workshop 2013

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Products and examples
MET in March 2013
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8th APMG Symposium/3rd SALGEE Workshop 2013

23. 8th APMG Symposium/3rd SALGEE Workshop 2013
Products and examples
MET in March 2013
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8th APMG Symposium/3rd SALGEE Workshop 2013

24. 8th APMG Symposium/3rd SALGEE Workshop 2013
Products and examples
MET in March 2013
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8th APMG Symposium/3rd SALGEE Workshop 2013

25. To see examples of applications come this afternoon to Alirio’s talk
Products and examples
To see examples of applications come this afternoon to Alirio’s talk
3rd SALGEE Workshop 2013
20 March 2013
Topic 1-2
Drought assessment & Fire risk forecast
14:50 15:05 Evapotranspiration: application in hydrology and drought monitoring
Alirio Arboleda, RMI
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26. 8th APMG Symposium/3rd SALGEE Workshop 2013
To get information
Where can I find information on the product, the methodology and the validation? 1.
a short description of the product
access to regularly updated documention
A product user manual (‘PUM’) to help you use
the product
An Algorithm Theoretical Basis document (‘ATBD’)
A Validation Report (‘VR’)
2. Open-access papers in Hydrology and Earth System Sciences
Ghilain, N., Arboleda, A., and Gellens-Meulenberghs, F.: Evapotranspiration modelling at large scale using near-real time MSG SEVIRI derived data, Hydrol. Earth Syst. Sci., 15, , doi: /hess , 2011
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27. 8th APMG Symposium/3rd SALGEE Workshop 2013
To get information
To discover our latest developments ?
3. Come to the next LSA-SAF workshop !
See:
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8th APMG Symposium/3rd SALGEE Workshop 2013

28. 8th APMG Symposium/3rd SALGEE Workshop 2013
To get information
Contact us !
LSA-SAF ET team from RMI
Françoise Meulenberghs
Alirio Arboleda
Nicolas Ghilain
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8th APMG Symposium/3rd SALGEE Workshop 2013

29. 8th APMG Symposium/3rd SALGEE Workshop 2013
Acknowledgments
To all validation data providers
EUMETSAT
ESA / PRODEX Program / BELSPO
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8th APMG Symposium/3rd SALGEE Workshop 2013

30. Thanks for your attention ! Questions ?
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8th APMG Symposium/3rd SALGEE Workshop 2013