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modeling and applications OF swot satellite data . C. Lion 1 , K.M. Andreadis 2 , R. Fjørtoft 3 , F. Lyard 4 , N. Pourthie 3 , J.-F. Crétaux 1 1 LEGOS/CNES, 2 Ohio State University/JPL 3 CNES, 4 LEGOS/CNRS. 1. SWOT mission. NASA and CNES, launch in 2019 - PowerPoint PPT Presentation
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MODELING AND APPLICATIONS OF SWOT SATELLITE DATA
C. Lion1, K.M. Andreadis2, R. Fjørtoft3,F. Lyard4, N. Pourthie3, J.-F. Crétaux1
1LEGOS/CNES, 2Ohio State University/JPL3CNES, 4LEGOS/CNRS
970
km
SWOT mission• NASA and CNES, launch in 2019• 970km orbit, 78°inclination, 22 days repeat• KaRIN: InSAR Ka band• Wide swath altimeter
• Ocean: “Low resolution” meso-scale and submeso-scalephenomena (10km and greater)
• Hydrology: “High resolution”surface area above (250m)² rivers above 100m
1
Preparing the mission for hydrology
2. SAR amplitude image: Rhone river, France CNES/ Altamira information simulator
1. Radar cross section CNES/ CAP Gemini simulator
Modelisation and simulation for technical use
2
Goals• Need for a simulator for scientific users (hydrology)– “Fast”: 3 months 3min– Easy to use: no need for heavy preparation of input data– Portable– Relatively realistic errors
• Targets: deltas, rivers, lakes…
• Output: water elevation
3
Simulator output: water heightThe Amazon river, Brazil
Simulator principle• Based on works of:
S. Biancamaria and M. Durand: swath calculation, principleV. Enjolras: residual error calculation
4
Simulator principle• Based on works of:
S. Biancamaria and M. Durand: swath calculation, principleV. Enjolras: residual error calculation
5
Simulator principle• Based on works of:
S. Biancamaria and M. Durand: swath calculation, principleV. Enjolras: residual error calculation
6
Residual height errors
Taken into account• Roll• Baseline variation• Thermal noise• Geometric
decorrelation• BAQ noise• Satellite position
Not taken into account yet• Troposphere• Layover• Shadow• Processing (classification…)• ….
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Residual height errors: Roll
• Roll
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H
h
B a
ir1r2
R
Residual height errors
• Baseline
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H
h
B
ir1r2
R
E_b
Residual height errors
• Coherence loss
g = gSNR + gSQRN + gg
N number of looks
10
H
h
B
ir1r2
R
Simulator principle• Based on works of:
S. Biancamaria and M. Durand: swath calculation, principleV. Enjolras: residual error calculation
11
Simulator principle• Based on works of:
S. Biancamaria and M. Durand: swath calculation, principleV. Enjolras: residual error calculation
12
m
Simulator principle• Based on works of:
S. Biancamaria and M. Durand: swath calculation, principleV. Enjolras: residual error calculation
13
Simulation: Ohio River
Input: Model LisFLOODReference water height (m)
Output: Water height observed by SWOT (m)
3 months modelization courtesy: K. Andreadis
40.5
40
39.5
39
38.5
40.5
40
39.5
39
38.5
Latit
ude
Latit
ude
275 276 277 278 279 275 276 277 278 279Longitude Longitude
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Assimilation methodology• Assimilating SWOT
observations in a identical twin synthetic experiment
• Ohio River study domain (only main stem)
• LISFLOOD hydraulic model• Ensemble Kalman filter• Errors introduced to boundary inflows, channel width,
depth and roughness• Observation errors from a Gaussian distribution
N(0,5cm)
15
courtesy: K. Andreadis
Assimilation results• Water surface elevation along the river channel at two SWOT
overpass times
208 Hours 280 Hours
• Information is not always propagated down/up stream• Small ensemble size could partly be the reason
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courtesy: K. Andreadis
Conclusions• Simulation of SWOT data with more representative errors
• The simulator is more user friendly: output format as input format, GUI, can be used with several models
• Can be used for assimilations studies (estimate indirect valuables)
• Need to improve the simulator: layover, decorrelation due to vegetation, troposphere …
17
Thank for your attention
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