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9. April 2023
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Closed loop brightness temperature data inversion for the retrieval of soil hydraulic properties
Marin Dimitrov, Jan Vanderborght, K. Z. Jadoon, Lutz Weihermüller, Mike Schwank and Harry Vereecken
2011 International Geoscience and Remote Sensing Symposium (IGARSS)Vancouver, Canada
Soil Moisture Remote Sensing Session
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OutlineOutline
I. Introduction1. Motivation2. Measurement setup3. Measurement equipment
II. Measurement Results
1. Soil moisture 2. Soil temperature 3. Brightness temperature
III. Inverse modeling
1. Flow chart diagram 2. Results
IV. Conclusions
Radiometer JülBaRa with Radiometer JülBaRa with holding construction in the air.holding construction in the air.
Photo from July 2010Photo from July 2010
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MotivationMotivation
• Investigation of the soil surface structure effects on the spatio-temporal soil moisture and soil temperature distribution
• Estimation of the relationship between the surface soil moisture and temperature and the subsurface states
• Implementation of classical (in-situ) and remote sensing methods
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Measurement campaignMeasurement campaignGoalsGoals
5TE and SDI Sensors 5TE and SDI Sensors
Radiometer JülBaRa Radiometer JülBaRa
• Monitoring of the soil moisture and soil temperature of plots with different soil structure
• Characterization and calibration of the L-Band Radiometer JülBaRa
• Monitoring of the L-band brightness temperature over bare soil ploughed plot
• Linking of the L-Band brightness temperature with the soil hydraulic properties
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Measurement campaignMeasurement campaignMeasurement setupMeasurement setup
1
2 1
2
Measurements plotsMeasurements plots
Ploughed plot Ploughed plot
Seedbed plot Seedbed plot
Reference plot Reference plot
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Measurement campaignMeasurement campaignMeasurement equipmentMeasurement equipment
Used measurement equipment. Pictures from test field Selhausen.Used measurement equipment. Pictures from test field Selhausen.
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Technical Characteristics:
• L Band Radiometer (λ ≈ 21 cm, f ≈ 1.4 GHz)• 2 channels (1.4-1.414 and 1.415-1.43 GHz)• Dual polarized conical horn antenna
• -3 dB beamwidth of 12°
Measuring cycle and operation:
• Calibrations at TCold = 278 & THot = 338K• Full cycle lasts for 45 s• Measuring software Labview• Rotation at horizontal and vertical direction
• 0 – 140° in horizontal direction• 48 – 140° in vertical direction
L Band RadiometerL Band RadiometerJülBaRaJülBaRa
Holding construction and rotation Holding construction and rotation possibilities of JülBaRapossibilities of JülBaRa
JülBaRa is in permanent use since September 2009
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ResultsResultsSoil moistureSoil moisture
Meteorological data and measured soil moisture in 2, 5, 10 and 30 cm Meteorological data and measured soil moisture in 2, 5, 10 and 30 cm depth between 27.09.2009 and 27.10.2009depth between 27.09.2009 and 27.10.2009
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ResultsResultsBrightness temperatureBrightness temperature
Measured brightness temperature (horizontal and vertical polarization) at Measured brightness temperature (horizontal and vertical polarization) at 45° with L-Band Radiometer JülBaRa between 27.09.2009 and 27.10.200945° with L-Band Radiometer JülBaRa between 27.09.2009 and 27.10.2009
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ResultsResultsSoil temperatureSoil temperature
Measured soil surface temperature Measured soil surface temperature from 02.10 to 07.10.2009from 02.10 to 07.10.2009
Photo from 2 October 2009 (12 P.M.)Photo from 2 October 2009 (12 P.M.)Plot 3Plot 2
16.6 °C16.6 °C 16.3 °C16.3 °C
15.4 °C15.4 °C
Mean skin temperature for the plotsMean skin temperature for the plots
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ResultsResultsModeling procedureModeling procedure
Flow chart diagram of the inverse modeling procedureFlow chart diagram of the inverse modeling procedureInversion for the soil hydraulic parameters, fitting of the brightness temperature Inversion for the soil hydraulic parameters, fitting of the brightness temperature
Soil hydraulic parameters:θr, θs, α, n, Ks
Hydrological simulator Hydrus 1D
Meteorological data: Rain and ETo (from Tair, Solar, Wind and Humidity)
Simulated moisture
profile
Simulated permitivity (ε)
profile
Dielectric mixing model
ε
Simulated Reflectivity
pSIMR
Tb sim.
Inversion
Objective function: Φ=Σ(Tb sim.-Tb meas.)^2
RTM
Roughness correction
CRTM or Fresnel
Tb meas.
θ sim.
.corrpSIMR
Global optimization with SCE
Effective soil temperature
θ meas
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ResultsResultsModeling procedureModeling procedure
Θr [cm^3/cm^3]
Θs [cm^3/cm^3]
α [cm^-1]
n [-]
Ks [cm/min]
Unknown hydraulic parameters: θr, θs, Ks, n and α
MVGθr
cm3
/cm3
θs
cm3
/cm3
α
1/cm
n-
Ks
cm/day
l-
Laboratory 0.0 0.353 0.004 1.32 0.064 0.5
Inverted 0.03 0.42 0.001 1.60 0.030 0.5
Parameter development after 1500 iterations, using Fresnel
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ResultsResultsModeling procedureModeling procedure
Modeled and measured brightness temperature, modeled and Modeled and measured brightness temperature, modeled and measured soil moisturemeasured soil moisture
R^2 = 0.75
One to one line of the brightness temperatureOne to one line of the brightness temperature
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ConclusionsConclusions
• Measurement plots with different soil surface structures
• Measurement of various soil moisture and soil temperature values in the different plots
• strong (0.2 – 5.6° C) variation of the soil surface temperature at the beginning of the campaign
• lowest soil surface temperature in the reference plot
• lowest soil moisture in the ploughed plot
• highly comparable soil moisture values in the reference and the seedbed plot
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ConclusionsConclusions
• Complex coupled inversion procedure for estimation of soil hydraulic parameters
• Coupling of six different models and some additional calculations
• Multi objective task: comparison of modeled and measured brightness temperatures, further evaluation of the soil moisture
• Innovative method for handling radiometer data, assessment of the soil hydraulic parameters
• Implementation of the inversion procedure for the other plots
• Improvement of the inversion procedure is still needed
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AcknowledgmentsAcknowledgments
The authors thanks to:
• Assist. Prof. Kosta Kostov, Bulgarian Academy of Sciences for all of the consultations
• Francois Jonard, Dr. Jutta Bikowski, Christian Steenpass and Dr. Ulrike Rosenbaum
• Rainer Harms, Normen Hermes and Ferdinand Engels
• The whole ZAT team and IBG Workshop
The Research Unit MUSIS gratefully acknowledge the financial support from the
Deutsche Forschugsgemeinschaft.
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Thank you for your attention!
Radiometer field of view from above, July 2010 Radiometer field of view from above, July 2010