Satellite altimetry over land surfaces€¦ · 1 Satellite altimetry over land surfaces -...

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Satellite altimetry over land surfaces

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Applications in hydrology

and for land surface properties

Frédéric Frappart email: [email protected]

XVth Rencontres du Vietnam - 8-14/09/2019 2nd VSEO Remote Sensing of Inundation, Flooding and Wetland

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1) Time series of water level

2) Time series of surface water volume

3) Time series of water discharge

4) Calibration/validation of hydrological models

5) Land surface properties and soil moisture

Contents


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Time series of water level


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Why monitoring water levels using radar

altimetry?

Negro River, Amazon

Lower acqisition period

(10 to 35 days)

Lower accuracy

(> 10 cm)

Larger number of stations than in situ networks Monitoring of rivers, lakes but also floodplains Same reference for all water stages


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• From a database

• Computed using a dedicated software

Time series of water level


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Lake levels: G-REALM

https://ipad.fas.usda.gov/cropexplorer/


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Lake and river levels: Hydroweb

http://hydroweb.theia-land.fr


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River and lake levels: DAHITI

https://dahiti.dgfi.tum.de


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River and lake levels: River & Lake


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Time series of surface water volume


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• Interpolation of altimetry-based water stages on the inundated

areas determined using satellite images (Frappart et al.,

Remote Sens. Env., 2005)

• Creation of hypsometric curves to

estimate the level of a flooded

pixel: h(λ,φ,t) = f(inundation(λ,φ,t) )

Frappart et al., Env. Res.

Lett. (2012)

• Determination of the surface water volume variations

Method


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MODIS-based (e.g., Sakamoto et al., Remote Sens. Env., 2007)

Surface water extent datasets


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GIEMS: Global Inundation Extent Multi-Satellite

Surface water extent datasets

Merging of satellite data with different wavelengths (surface classification, NN, vegetation)

Passive microwave SSM/I emissivities at 19, 37 GHz, H and V polarizations

Active microwave ERS scatterometer backscattering coefficient at 5.25 GHz

Visible and near infrared AVHRR NDVI (visible and near-infrared reflectances)

[Prigent et al., J. Geophys. Res., 2007; Geophys. Res. Lett., 2012 Papa et al., Geophys. Res. Lett., 2006; 2008; J. Geophys. Res., 2010]

Mean fractional surface water extent at annual maximum

Data mapped on equal-area grid with 0.25°x0.25° resolution at equator (773 km²)

Monthly resolution for 1993-2007 (soon 5 days)

and at least extended to 2012 and longer

%


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Examples of surface water volume variations

Frappart et al., Sci. Tot. Env.

(2018)


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Frappart et al., Sci. Tot. Env. (2018)


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Frappart et al., Env. Res. Lett. (2012)

Silva et al., Int. J. Remote Sens. (2012)

Papa et al., J. Geophys. Res. (2010)

543 stations altimétriques

ENVISAT RA-2


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Frappart et al., Environ. Res.

Lett. (2012)


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Time series of water discharge


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River profile

Average river profile of the Amazon mainstem during the 1995-

1996 hydrological cycle (Birkett et al., J. Geophys. Res., 2002)


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River discharge

• Using a rating curve based on in situ discharges:

(Rantz et al., 1982)

for a single satellite altimetry mission:

(Zakharova et al., C. R. Geosci., 2006)


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River discharge

For multiple satellite altimetry missions:

(Bogning et al., Remote Sens., 2018)


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River discharge

• Using rating curves based on simulated discharges from a

hydrological model:

(Paris et al., Water Resour. Res., 2016)


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Calibration/validation of hydrological models


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Validation of hydrological models

Hydrodynamics modeling of the central Amazon using LISFLOOD

(Wilson et al., Geophys. Res. Lett., 2007)

River

Floodplain + model

o altimetry

Topex/Poseidon Track


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Validation of hydrological models

Hydrodynamics modeling of the Amazon using MGB-IPH (Paiva et

al., Water Resour. Res., 2013)


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Assimlation into hydrological models

Hydrodynamics modeling of the Amazon using MGB-IPH (Paiva et

al., Water Resour. Res., 2013)


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Land surface properties and soil moisture


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Global maps of radar altimetry backscatering

ENVISAT (Ku)

ENVISAT (S)


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ENVISAT (Ku)

SARAL (Ka)


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ENVISAT (Ku)

ENVISAT (S)


31 Télédétection RADAR : théorie et applications dans le domaine de l'environnement


ENVISAT (Ku)

SARAL (Ka)

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Backscattering as a function of frequency

Frappart et al., Phys. Chem. Earth (2015)


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Backscattering as a function of frequency

Frappart et al., Phys. Chem. Earth (2015)


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Backscattering as a function of incidence

Fatras et al., Remote Sens. Env. (2015)


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Soil moisture inversion

Soil moisture inversion over

sand surfaces insemi-arid

areas

Fatras et al., Remote Sens.

Env. (2012)


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Flood extent estimates

Papa et al., Int. J. Remote Sens. (2006)

% of inundation (July 1993)

Months with floods

Flood if σ0 > 20 dB at C-band using Topex/Poseidon Flood extent incresases of 4% when σ0 increases of 1 dB


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