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  1. 1. 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
  2. 2. Outline <ul><li>I. Introduction </li></ul><ul><ul><li>Motivation </li></ul></ul><ul><ul><li>Measurement setup </li></ul></ul><ul><ul><li>Measurement equipment </li></ul></ul><ul><li>II. Measurement Results </li></ul><ul><li> 1. Soil moisture </li></ul><ul><li> 2. Soil temperature </li></ul><ul><li> 3. Brightness temperature </li></ul><ul><li>III. Inverse modeling </li></ul><ul><li> 1. Flow chart diagram </li></ul><ul><li> 2. Results </li></ul><ul><li>IV. Conclusions </li></ul>Radiometer JülBaRa with holding construction in the air. Photo from July 2010
  3. 3. Motivation <ul><ul><li>Investigation of the soil surface structure effects on the spatio-temporal soil moisture and soil temperature distribution </li></ul></ul><ul><ul><li>Estimation of the relationship between the surface soil moisture and temperature and the subsurface states </li></ul></ul><ul><ul><li>Implementation of classical (in-situ) and remote sensing methods </li></ul></ul>
  4. 4. Measurement campaign Goals <ul><ul><li>Monitoring of the soil moisture and soil temperature of plots with different soil structure </li></ul></ul><ul><ul><li>Characterization and calibration of the L-Band Radiometer JülBaRa </li></ul></ul><ul><ul><li>Monitoring of the L-band brightness temperature over bare soil ploughed plot </li></ul></ul><ul><ul><li>Linking of the L-Band brightness temperature with the soil hydraulic properties </li></ul></ul>5TE and SDI Sensors Radiometer JülBaRa
  5. 5. Measurement campaign Measurement setup 1 2 1 2 Measurements plots Ploughed plot Seedbed plot Reference plot
  6. 6. Measurement campaign Measurement equipment Used measurement equipment. Pictures from test field Selhausen.
  7. 7. <ul><li>Technical Characteristics: </li></ul><ul><li>L Band Radiometer (λ ≈ 21 cm, f ≈ 1.4 GHz) </li></ul><ul><li>2 channels ( 1.4-1.414 and 1.415-1.43 GHz ) </li></ul><ul><li>Dual polarized conical horn antenna </li></ul><ul><ul><li>-3 dB beamwidth of  12° </li></ul></ul><ul><li>Measuring cycle and operation: </li></ul><ul><li>Calibrations at T Cold = 278 & T Hot = 338K </li></ul><ul><li>Full cycle lasts for  45 s </li></ul><ul><li>Measuring software Labview </li></ul><ul><li>Rotation at horizontal and vertical direction </li></ul><ul><ul><li>0 – 140° in horizontal direction </li></ul></ul><ul><ul><li>48 – 140° in vertical direction </li></ul></ul>L Band Radiometer JülBaRa Holding construction and rotation possibilities of JülBaRa JülBaRa is in permanent use since September 2009
  8. 8. Results Soil moisture Meteorological data and measured soil moisture in 2, 5, 10 and 30 cm depth between 27.09.2009 and 27.10.2009
  9. 9. Results Brightness temperature Measured brightness temperature (horizontal and vertical polarization) at 45° with L-Band Radiometer JülBaRa between 27.09.2009 and 27.10.2009
  10. 10. Results Soil temperature Measured soil surface temperature from 02.10 to 07.10.2009 Photo from 2 October 2009 (12 P.M.) Plot 3 Plot 2 16.6 °C 16.3 °C 15.4 °C Mean skin temperature for the plots
  11. 11. Results Modeling procedure Flow chart diagram of the inverse modeling procedure 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 Tb sim. Inversion Objective function: Φ = Σ (T b sim. -T b meas. )^ 2 RTM Roughness correction CRTM or Fresnel Tb meas. θ sim. Global optimization with SCE Effective soil temperature θ meas
  12. 12. Results Modeling procedure Unknown hydraulic parameters: θ r, θ s, Ks, n and α Parameter development after 1500 iterations, using Fresnel Θ r [cm^3/cm^3] Θ s [cm^3/cm^3] α [cm^-1] n [-] Ks [cm/min] MVG θ r cm 3 /cm 3 θ s cm 3 /cm 3 α 1/cm n - K s 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
  13. 13. Results Modeling procedure Modeled and measured brightness temperature, modeled and measured soil moisture R^2 = 0.75 One to one line of the brightness temperature
  14. 14. Conclusions <ul><ul><li>Measurement plots with different soil surface structures </li></ul></ul><ul><ul><li>Measurement of various soil moisture and soil temperature values in the different plots </li></ul></ul><ul><ul><ul><li>strong (0.2 – 5.6° C) variation of the soil surface temperature at the beginning of the campaign </li></ul></ul></ul><ul><ul><ul><li>lowest soil surface temperature in the reference plot </li></ul></ul></ul><ul><ul><ul><li>lowest soil moisture in the ploughed plot </li></ul></ul></ul><ul><ul><ul><li>highly comparable soil moisture values in the reference and the seedbed plot </li></ul></ul></ul>
  15. 15. Conclusions <ul><ul><li>Complex coupled inversion procedure for estimation of soil hydraulic parameters </li></ul></ul><ul><ul><ul><li>Coupling of six different models and some additional calculations </li></ul></ul></ul><ul><ul><ul><li>Multi objective task: comparison of modeled and measured brightness temperatures, further evaluation of the soil moisture </li></ul></ul></ul><ul><ul><li>Innovative method for handling radiometer data, assessment of the soil hydraulic parameters </li></ul></ul><ul><ul><li>Implementation of the inversion procedure for the other plots </li></ul></ul><ul><ul><li>Improvement of the inversion procedure is still needed </li></ul></ul>
  16. 16. Acknowledgments <ul><li>The authors thanks to: </li></ul><ul><li>Assist. Prof. Kosta Kostov, Bulgarian Academy of Sciences for all of the consultations </li></ul><ul><li>Francois Jonard, Dr. Jutta Bikowski, Christian Steenpass and Dr. Ulrike Rosenbaum </li></ul><ul><li>Rainer Harms, Normen Hermes and Ferdinand Engels </li></ul><ul><li>The whole ZAT team and IBG Workshop </li></ul>The Research Unit MUSIS gratefully acknowledge the financial support from the Deutsche Forschugsgemeinschaft.
  17. 17. Thank you for your attention! Radiometer field of view from above, July 2010