L-Band Radiometry for Sea-Ice Applications
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L-Band Radiometry for Sea-Ice Applications Georg Heygster1, Stefan Hendricks2, Lars Kaleschke3, Nina Maass3, Peter Mills1, Detlef Stammer3, Rasmus T. Tonboe4, and Christian Haas5 1) Institute of Environmental Physics, University of Bremen, Germany 2) Alfred-Wegener-Institute for Polar and Marine Research, Bremerhaven, Germany 3) Institute of Oceanography, University of Hamburg, Germany 4) Danish Meteorological Institute, Copenhagen, Denmark 5) University of Alberta, Edmonton, Canada Final Report for ESA ESTEC Contract 21130/08/NL/EL Institute of Environmental Physics, University of Bremen November 2009 ii L-Band Radiometry for Sea Ice Applications iii iv Contents 0.1 List of symbols . ix Abstract 1 1 Introduction 3 2 WP1: Literature Review 7 2.1 Introduction . .7 2.2 Physical properties of sea ice . .8 2.2.1 Formation processes . .8 2.2.2 Emissivity modelling . .9 2.2.3 Emissivity Measurements . 10 2.3 Passive Microwave Remote Sensing of Sea Ice Properties . 11 2.3.1 Ice type and concentration . 11 2.3.2 Thickness and other variables . 13 2.3.3 Emissivity of sea water . 14 2.4 Remote detection of sea ice from other instruments . 14 2.4.1 Inferring ice thickness from observables using physical models . 15 2.4.2 SAR applications to ice remote sensing . 15 2.5 Existing L-band sea ice observations . 16 2.5.1 Skylab . 16 2.5.2 Meltpond 2000 . 18 2.5.3 Pol-Ice 2007 . 18 2.6 Conclusion . 20 3 WP 2.2: POL-ICE campaign: Ice thickness observations 23 3.1 Introduction . 23 3.2 EM Data Processing . 25 3.2.1 EM Principle . 25 3.2.2 Sampling . 26 3.2.3 Limitations of the EM technique . 26 3.2.4 Thickness Bias . 26 3.2.5 Filtering . 29 3.3 Deliverable . 29 3.3.1 EM data files . 29 3.3.2 Data Format . 31 3.4 Navigational accuracy . 31 v vi 4 WP 2.1: Campaign data analysis; WP 2.5: Ice concentration vs. ice thickness 35 4.1 Abstract . 35 4.2 Model description . 36 4.2.1 Brightness temperature . 36 4.2.2 Water emissivity . 36 4.2.3 Sea ice emissivity . 38 4.3 Data . 43 4.4 Results . 46 4.4.1 Thickness . 47 4.4.2 Concentration . 48 4.4.3 Arctic simulation using a thermodynamic sea ice model . 48 4.5 Errors of the thickness retrieval . 58 4.6 Discussion and conclusions . 58 4.6.1 Ice concentration . 59 4.6.2 Ice temperature . 59 4.6.3 Ice salinity . 60 4.6.4 Ice roughness . 60 4.6.5 Ice thickness distribution and ice volume . 60 4.6.6 Conclusion . 60 4.7 Appendix A - Selected homogeneous regions . 61 4.8 Appendix B - EMIRAD tracks . 62 4.9 Appendix C - Source codes . 62 4.9.1 Despiking filter code . 62 4.9.2 Module: emissivity model . 75 4.9.3 Module: Brine volume . 76 4.9.4 Main: model test . 78 5 WP 2.3a Stokes components Tv, Th from combining thermodynamic and emissivity models 81 5.1 Introduction . 81 5.2 Microwave emission from sea ice . 83 5.3 Sensitivity study . 83 5.4 The combined thermodynamic and emission model . 83 5.5 The interface between the thermodynamic and the emission models . 85 5.6 Combined thermodynamic and emissivity model simulation results . 86 5.7 Conclusions . 86 6 WP 2.3b: Foward modelling of the first two Stokes components using Combined Strong Fluctuation Theory (CSFT) 97 6.1 Introduction . 97 6.2 Theory . 98 6.2.1 Strong Fluctuation Theory . 98 6.2.2 Combined Strong Fluctuation Theory . 99 6.2.3 Coherent solution . 101 6.2.4 Mixture models of effective permittivity . 101 6.3 Special models . 103 L-Band Radiometry for Sea Ice Applications vii 6.3.1 Ridged Monte Carlo model . 103 6.3.2 Three-layer models . 103 6.4 Frequency dependence for model ice profiles . 107 6.4.1 Standard profiles . 107 6.4.2 Parameterized model profiles . 112 6.5 Detailed comparison of mixture formulae . 113 6.6 Intercomparison study . 118 6.7 Forward modelling of Pol-Ice data . 127 6.8 Conclusion . 127 7 WP 2.4a: Forward modelling Stokes components U and V 129 7.1 Introduction . 129 7.2 The Stokes vector . 129 7.3 A simple model . 130 7.4 Simulation results . 131 7.5 WindSat polarimetric measurements at 10, 18 and 37 GHz . 131 7.6 Conclusions . 131 8 WP 2.4b: Modelling the third Stokes component from geometric considerations 135 8.1 Introduction . 135 8.2 Theory . 136 8.3 Experimental support: PolICE 2007 . 139 8.4 Ridged ice . 142 8.5 Conclusion . 146 9 Extrapolation to other salinities 147 9.1 Introduction . 147 9.2 Data . 147 9.2.1 Pol-Ice campaign . 147 9.2.2 Processing and collocation procedures . 148 9.2.3 EMIRAD instrument characteristics . ..