Surface Water Fraction from SMOS data
Ahmad AL Bitar (CNRS/CESBIO)
Marie Parrens, Remi Cote, Jean-Pierre Wigneron,
Philippe Richaume, Yann Kerr
2nd SMOS Science Conference ,ESA-ESAC, Villafranca, Spain, 2015
Al Bitar et al.
SWaF
Introduction
2nd SMOS Science Conference ,ESA-ESAC, Villafranca, Spain, 2015
Al Bitar et al.
SWaF - SMOS Water Fraction
Fractional area covered with ponding or open
water, for an area of 25x25 km, over Tropical
watersheds.
60 %
Other
40 %
Water
2nd SMOS Science Conference ,ESA-ESAC, Villafranca, Spain, 2015
Al Bitar et al.
Surface water fraction from RS
Technology
Optical
SAR
Microwave
Spatial
resolution
Temporal
sampling
All
Weather
Impact of
Vegetation
++
+
-
-+
-
Abarca et al. 2012
--
Sippel et al .1998
Prigent et al. 2001
-
+
+
ref.
Hess et al. 2003
Courtesy of F. Frappard (LEGOS)
What is the potential of SMOS to map water surfaces ?
2nd SMOS Science Conference ,ESA-ESAC, Villafranca, Spain, 2015
Al Bitar et al.
The Mississippi Flooding
Shown at the SMOS 1st Workshop, Arles, 2011
Ponding effect during rainfall was reported in
several papers (Al Bitar et al. 2012, Jackson et
al. 2012)
2nd SMOS Science Conference ,ESA-ESAC, Villafranca, Spain, 2015
Al Bitar et al.
FOrest Soil Moisture EXperiment (FOSMEX)
No foliage
with foliage
2.5h
~3K
2.5h
~3K
Courtesy of M. Schwank
2nd SMOS Science Conference ,ESA-ESAC, Villafranca, Spain, 2015
Al Bitar et al.
2nd SMOS Science Conference ,ESA-ESAC, Villafranca, Spain, 2015
Al Bitar et al.
SWaF
Data & Methods
Region of interest
Data analysis
2nd SMOS Science Conference ,ESA-ESAC, Villafranca, Spain, 2015
Methods
Al Bitar et al.
Regions of interest
Amazon Basin
British Library - Amazon riverside
6 million km2
< Surface >
209 000 m3/s
< Outflow >
2 cm/km at the exit
15 % of freshwater to ocean
<
Slop
>
< Relevant >
2nd SMOS Science Conference ,ESA-ESAC, Villafranca, Spain, 2015
Al Bitar et al.
Regions of interest
Amazon Basin
Congo Basin
Lac Tanganyika
Lac Mweru
British Library – Afrixalus Frog
6 million km2
< Surface >
3.7 million km2
209 000 m3/s
< Outflow >
41 800 m3/s
2 cm/km at the exit
15 % of freshwater to ocean
<
Slop
>
< Relevant >
2nd SMOS Science Conference ,ESA-ESAC, Villafranca, Spain, 2015
0-5000 altitude
2nd biggest river basin
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Al Bitar et al.
Seasonal dynamics in tropical watersheds
Congo
Amazon
basin
TBh percentiles at 0.9, ascending orbits ,
3 months separation , 42.5
2nd SMOS Science Conference ,ESA-ESAC, Villafranca, Spain, 2015
AL Bitar A., CESBIO
Al Bitar et al.
Timeseries over Amazon basin
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Topography ?
Vegetation dynamics ?
Soil Moisture ?
Physical temperature ?
Water surfaces ?
2nd SMOS Science Conference ,ESA-ESAC, Villafranca, Spain, 2015
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Al Bitar et al.
Timeseries over Amazon basin
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
Topography ?
Vegetation dynamics ?
Soil Moisture ?
Physical temperature ?
Water surfaces ?
2nd SMOS Science Conference ,ESA-ESAC, Villafranca, Spain, 2015
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Al Bitar et al.
Timeseries over Amazon basin

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
Topography ?
Vegetation dynamics ?
Soil Moisture ?
Physical temperature ?
Water surfaces ?
2nd SMOS Science Conference ,ESA-ESAC, Villafranca, Spain, 2015
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Al Bitar et al.
Timeseries over Amazon basin
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

Topography ?
Vegetation dynamics ?
Soil Moisture ?
Physical temperature ?
Water surfaces ?
2nd SMOS Science Conference ,ESA-ESAC, Villafranca, Spain, 2015
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Al Bitar et al.
Timeseries over Amazon basin
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Topography ?
Vegetation dynamics ?
Soil Moisture ?
Physical temperature ?
Water surfaces ?
e p (t , θ ) ≈
2nd SMOS Science Conference ,ESA-ESAC, Villafranca, Spain, 2015
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TB p (t , θ )
TSKT (t )
Al Bitar et al.
Double component radiative modeling
TB p ,Mixt (t ,θ ) = SWaFp ⋅ TB p ,eau + (1 − SWaFp )⋅ TB p ,Other
TB mixte
TB Water
other
TB Other
SWaF
2nd SMOS Science Conference ,ESA-ESAC, Villafranca, Spain, 2015
Al Bitar et al.
Water Brightness temperature
Fresnel law for Freshwater reflectivity
2nd SMOS Science Conference ,ESA-ESAC, Villafranca, Spain, 2015
Al Bitar et al.
Algorithm
L3 TB H/V
Forest and water
temperature
Moyemp±2.58σ
Filter for outlayers
Double component
radiative transfert
Temporal
interpolation
SWaF
2days
Monthly averaging
SWaF
monthly
2nd SMOS Science Conference ,ESA-ESAC, Villafranca, Spain, 2015
Al Bitar19
et al.
Monthly SWaF - SMOS Water Fraction
Monthly Surface Water Fraction over Amazone
2nd SMOS Science Conference ,ESA-ESAC, Villafranca, Spain, 2015
Al Bitar et al.
Monthly SWaF - SMOS Water Fraction
Monthly Surface Water Fraction over Congo
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Al Bitar et al.
SWaF
Results
Landcover
Altimeters
2nd SMOS Science Conference ,ESA-ESAC, Villafranca, Spain, 2015
Climate
Al Bitar et al.
SWaF and Landcover maps
GC
Globcover
< Long name >
22 + 1
< Classes
>
MERIS
<
>
Sensor
~ 300 m
< Resolution >
ESA
< Provider >
Arino et al., 2008
< Sources & ref. >
2nd SMOS Science Conference ,ESA-ESAC, Villafranca, Spain, 2015
Al Bitar et al.
SWaF and Landcover maps
GC
Globcover
IGBP
< Long name >
International Geosphere
Biosphere Programme
22 + 1
< Classes
>
17
MERIS
<
>
MODIS
~ 300 m
< Resolution >
~ 500 m
ESA
< Provider >
Univ. of Arizona/USGS
Arino et al., 2008
< Sources & ref. >
Broxton et al., JAMC, 2014
Sensor
2nd SMOS Science Conference ,ESA-ESAC, Villafranca, Spain, 2015
Al Bitar et al.
SWaF and Landcover maps
GLOBCOVER
aggregated to 25km EASE
IGBP
aggregated to 25km EASE
2nd SMOS Science Conference ,ESA-ESAC, Villafranca, Spain, 2015
Al Bitar et al.
SWaF and Landcover maps
2nd SMOS Science Conference ,ESA-ESAC, Villafranca, Spain, 2015
Al Bitar et al.
SWaF and Landcover maps
2nd SMOS Science Conference ,ESA-ESAC, Villafranca, Spain, 2015
Al Bitar et al.
SWaF and Altimeters
2nd SMOS Science Conference ,ESA-ESAC, Villafranca, Spain, 2015
Al Bitar et al.
Jason2 – Water height
SMOS Water Fraction (SWaF)
SWaF and Altimeters
Pearson corr.: 0.98
Jason2 river height from Hydroweb Legos (J.F. Creteaux)
2nd SMOS Science Conference ,ESA-ESAC, Villafranca, Spain, 2015
Al Bitar et al.
SWaF and Climate regimes
2nd SMOS Science Conference ,ESA-ESAC, Villafranca, Spain, 2015
Al Bitar et al.
SWaF and Climate regimes
3 to 4 months
A phase shift of 4 months in accordance with the phase shift of rainfall observed in
(Molonier et al., 1996)
2nd SMOS Science Conference ,ESA-ESAC, Villafranca, Spain, 2015
Al Bitar et al.
SWaF
Conclusions
2nd SMOS Science Conference ,ESA-ESAC, Villafranca, Spain, 2015
Al Bitar et al.
SWaF
SMOS Water Fraction over Tropical watersheds
•
•
•
•
•
is an innovative new application of SMOS
shows good agreement with Landcover maps
is highly correlated to water height in flat areas
is usefull for global water and carbon cycle studies
needs CAL/VAL and improvements
2nd SMOS Science Conference ,ESA-ESAC, Villafranca, Spain, 2015
Al Bitar et al.
Thank you.
Tomorow afternoon presentation by Beatriz Molero, Arnaud Mialon and Ahmad Al Bitar
on CATDS products and new L4 SMOS applications.
2nd SMOS Science Conference ,ESA-ESAC, Villafranca, Spain, 2015
Al Bitar et al.