FR4.L10.2: A MICROWAVE SCATTERING MODEL OF VEGETATED SURFACES BASED ON BOR/DDA AND NMM3D FOR SMAP MISSION
1. A MICROWAVE SCATTERING MODEL OF VEGETATED SUFACES BASED ON BOR & NMM3D FOR SMAP MISSION XiaolanXu, Shaowu Huang, Leung Tsang EE, University of Washington, Seattle, WA Seung-Bum Kim, EniNjoke JPL, California Institute of Technology, Pasadena, CA IGARSS 2010, Honolulu, Hawaii July 25 -30
3. Background – SMAP mission Soil Moisture Active/Passive (SMAP) mission L-band (1.26GHz) combined microwave system Global maps of the Earth’s soil moisture Radar Backscatter product with 3 km resolution Requirements Estimates of top 5-cm soil moisture Excluding regions of snow and ice, mountainous topography, open water, and VWC > 5kg/m2
4. Physical Forward Model Vegetation Layer Interaction Soil Surface Snapshot Time-Series 3D DATA CUBE (N classes) NDVI Class 1 Soil Moisture Invert Invert Invert Invert HV HV Reassemble Spatial Map ••••• ••••• ••••• ••••• To Archive To Archive Radar Level One Data Radar Level One Data VV VV Classification Classification Classification Classification Soil Moisture HH HH Invert Class n Corn Field Flag Data Not valid Unable to invert Topography (SRTM) Grass Land Soybean Field Flow Chart
5. Baseline Retrieval Algorithm An optimization process applied to a robust physical forward model Data Cube – Generate according to the vegetation type Retrieval Algorithm – Least squared Method Minimize d
6. Data Cube - Advantages Accuracy 3D Numerical solution of Maxwell’s Equations for both rough surface scattering and volume scattering to ensure accuracy Time Fast algorithm has been applied for scattering calculation. (Surface: PBTG/SMCG; Volume: BOR) Pre-calculated Look-up table Interpolation Robust
7. Background - SMAP mission Baseline Algorithm - Flow Chart Data Cube Representation Soil - Rough Surface Scattering Vegetation – Volume Scattering Interaction Data Comparison Summary Region 0 Region 1 Region 2 Outline
8. Soil - Rough Surface Scattering Bared surface – Numerical Method (NMM3D) Generate profile of 3D random rough surface for each realization, using exponential correlation functions Solve Maxwell Equations Based on Method of Moment (MoM) solution of Maxwell Equations Accelerated by fast algorithm S. Huang et, al. TGARSS vol.48, no.6, pp.2557-2568, 2010 Implemented on parallel computing
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11. Coherent reflectivity Relative permittivity = 15.14+i*1.27, rms height are normalized in wavelength correlation length = 10*rms height.
15. Distribution function of a group of cylinders The bistatic function depends on the orientation angles of the cylinders. The averaging is taken as followed,
16. Vegetated rough surface Region 0 Region 1 Region 2 Half Space Greens’ Function The coherent reflectivities Rv and Rh is calculated by NMM3D
18. Grass Land Comparison Southern Great Plains (SGP) 1999 Experiment Passive and Active L & S System (PALS) L-band VV, HH, VH channel Incident angle 40 Typical Condition in Grass land Thin cylinders, more uniform distribution
23. Site 5: Discussion mv is low, hh > vv mv increase, hh < vv HH dominant by vegetation effect (volume scattering + double bounce) VV dominant by soil effect (surface scattering)
24. Further more… how about cross-pol? Cross-pol from soil is done by Oh. Model. Cross-pol is underestimated Distribution of vegetation Accurate cross-pol from soil
25. Summary SMAP Baseline Algorithm Data cube representation More accurate by using numerical method Fit into the retrieval algorithm by using Look up table with interpolation Robust tune up Good Agreement with SGP 99 measurement
26. Ongoing Research Rough Surface Accurate cross-polarization Vegetation Multilayer to include more complicate structure Interaction Include incoherent reflection Data validation of more types of crops
27. Acknowledgement Shaowu Huang, Prof. Leung Tsang Dr. Seung-Bum Kim, Dr. EniNjoke NASA, JPL Thanks for your attention! QUESTION?
