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Appendix A: Surface Emissivity Data from Microwave Experiments of the University of Bern

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Appendix A: Surface Emissivity Data from Microwave Experiments of the University of Bern
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   Appendix A: Surface Emissivity Data from Microwave Experiments of the University of Bern Christian Mätzler and Andreas Wiesmann Purpose : Surface-based microwave signature studies from 2 to 100 GHz were carried out over years to provide empirical emissivity information for typical surface classes. The surface emissivity e  p  (polarization  p ) was determined from the effective object temperature T  eff  , the  brightness temperatures T   p  of the object under investigation and    of the downwelling sky radiation T  sky  in the relevant direction, using the relationship: e  p = ( T   p   -  T  sky )/( T  eff  -T  sky ), ranging from 0 to 1. The data presented here are based on measurements made with the PAMIR system operating at 4.9, 10.4, 21, 35 and 94 GHz (Mätzler, 1987 to 1994) and with a set of newer portable radiometers at 11, 21, 35, 48 and 94 GHz (Weise, 1996; Wiesmann et al. 1996, Wiesmann et al. 1998, Mätzler et al. 1997). Additional experiments – not reported here – were made with the RASAM instrument, a combined radiometer and scatterometer, operating over the frequency range from 2 to 12 GHz. Data collected with this instrument are reported in a separate catalog (Wegmüller and Mätzler, 1993) which was described by Wegmüller et al. (1994). Applications : To extract emissivity information, either directly from the data catalog or through a fast, empirical model, and to test microwave emissivity models.  References Mätzler C. "Applications of the Interaction of Microwaves with the Natural Snow Cover", Remote Sensing Reviews, Vol. 2, pp. 259-392 (1987). Mätzler C. "Seasonal evolution of microwave radiation from an oat field", Remote Sensing Environment Vol. 31, pp. 161-173 (1990). Mätzler C. "Microwave transmissivity of a forest canopy: Experiments made with a beech, Remote Sensing of Environment, Vol. 48, pp. 172-180 (1994). Mätzler C. "Passive microwave signature catalog 1989-1992" (Vol.1), IAP-Report, Feb. (1993), Vol. 2. May 1994, Vol. 3, July (1994). Mätzler C. "Passive microwave signatures of landscapes in winter", Meteorology and Atmos- pheric Physics, Vol. 54, pp. 241-260 (1994). Mätzler C., T. Strozzi, T. Weise, D. Floricioiu and H. Rott, "Microwave snowpack studies made in the Austrian Alps during the SIR-C/X-SAR experiment", Internat. J. Remote Sensing, Vol. 18, pp. 2505-2530 (1997). Wegmüller U. and C. Mätzler, "Active and passive microwave signature catalogue (2-12 GHz)", IAP-Bericht, März (1993). Wegmüller U., C. Mätzler, R. Hüppi und E. Schanda, "Active and passive microwave signature catalogue on bare soil (2-12 GHz)", IEEE Trans. Geoscience and Remote Sensing, Vol. 32(3), pp. 698-702 (1994). Weise T. "Radiometric Data (11-94 GHz) and Autocorrelation functions of dry snow samples", Res. Report No. 96-2, Institute of Applied Physics, Univ. of Bern (1996). Wiesmann A., T. Strozzi and T. Weise, "Passive microwave signature catalogue of snowcovers at 11, 21, 35, 48 and 94 GHz", Res. Report No. 96-8, Institute of Applied Physics, Univ. of Bern (1996). Wiesmann A., C. Mätzler and T. Weise, "Radiometric and structural measurements of snow samples", Radio Science, Vol. 33, pp. 273-289 (1998).  Instrument characteristics PAMIR main system parameters, for more details, see Mätzler (1987); the portable radiome-ters have similar characteristics with an additional frequency at 48 GHz. Variables: frequency: 5 selectable, any incidence angle select-able: 50° to 55°, full-beam width 9° to 10°, polarization: linear h,v, and intermediate values 4.9 GHz10.4 GHz21 GHz 35 GHz 94 GHz Measurement precision, ∆ T (K), at integration time of 1 s 0.1 0.1 0.1 0.1 0.2 Expected absolute error of brightness temperatures T v , T h  (K) 1 1 1 1 2 Expected error of mean emissivity e p = ( T p   -  T sky )/( T eff  -T sky ), p=h,v   0.0050.0050.005 0.005 0.01 Expected error of polarization difference, e v -e h   0.0030.0020.002 0.002 0.005   Standard ground-truth parameters WE (mm) Water Equivalent depth of snowpack (equivalent height of water column) Hsnow (cm) Snow height dw (mm) Equivalent depth of vegetation canopy water, also known as canopy water content h (cm) Height of vegetation canopy mg Gravimetric soil moisture (water mass/dry-soil mass) ε ’ Real part of relative dielectric constant of the top 8 mm soil at about 1 GHz ρ  (g/cm 3 )  Dry soil density Teff (C) Effective temperature of surface used to compute the emissivity Tair, Tveg, Tsoil (C)  Air, vegetation and soil temperature, respectively  Test sites, objects and data Object classes and test sites Object Class Test Site Object-class description YOUNG BARLEY 7 situations of green winter barley crop in spring 1990, height from 15 to 100 cm, T>3°C YOUNG OAT 17 situations of green oat crop in spring 1989, height from 16 to 84 cm, T>7°C (Mätzler, 1990) UNFROZEN GRASS Combines the classes of unfrozen grass: SHORT, MEDIUM and HIGH SHORT GRASS 9 situations with grass cover, height 5 - 10 cm, volumetric soil moisture 13% to 60%, grass temperature above -1°C. MEDIUM GRASS 4 situations of grass cover with height between 15 and 32 cm, Tveg > 5°C. HIGH GRASS 6 situations of grass cover with height between 32 and 55 cm, Tveg > 10°C. GRASS AFTER SNOW 2 situations, just after snowmelt, when short grass was still pressed to the wet ground FROST GRASS 3 situations of short grass with hoar frost at temperatures between -5°C and –2°C, frozen soil at –2 to –0.8°C. FROZEN GRASS 4 situations of short, frozen grass without hoar frost at temperatures from – 5 to -1.7°C, soil at –2 to 0°C (one situation with unfrozen soil). FROZEN SOIL 2 situations of frozen, bare soil with surface temperatures of -6°C and -1°C, respectively, mostly frozen soil moisture of about 40% by volume, see low ε ’ at 1GHz. BARE SOIL 9 situations of unfrozen, bare sandy-loam soil at temperatures between 0 and 25°C, volumetric soil moisture between 12% and 45%, roughness height about 1 cm. POWDER SNOW 5 situations of 8 to 37 cm deep powder snow of Dec. 1990 and Nov. 1993 at T from -3 to -13°C, with WE up to 5 cm. The grass-covered soil was unfrozen, except for 1 case. Most of the dry snow was 1 to 7 days old. THIN CRUST 5 situations in Nov. and Dec. 1990 of thin refrozen crusts on wet snow. BOTTOM CRUST 2 situations of aged, refrozen snow (depths of 6 and 15 cm) on short grass and frozen ground. WET SNOW Tannacker, agri-cultural field in Moosseedorf, near Bern, Switzerland Long.: 7.48°E Lat.:47.0°N  Altitude: 570 m a.s.l., sandy-loam soil, dry-soil density: 0.9 to 1.2 g/cm 3  pixel size: 1 m 2  4 situations of wet snow on short grass and unfrozen ground SLF_BARE 9 situations of the snow-free test site in wet and dry, unfrozen condition SLF_BOTTOMCRUST 6 situations of a special snow situation observed in late 1984 and early 1985. An abundant snow fall in autumn 1984 metamorphosed to a 40 cm thick, hard crust and formed the bottom of the new winter snowcover. The crust was frozen to the ground, and subsequently covered by new snow. SLF_DEEP 50 situations of deep winter snow with WE between 25 and 63 cm SLF_ MEDIUM 12 situations of winter snow with WE between 10 and 25 cm SLF_ SHALLOW 11 situations of winter snow with water equivalents (WE) between 4 and 10 cm. Winter snow is dry, and it has not undergone melt metamorphism SLF_THICKCRUST 15 situations of wet snow covered by a 4 to 30 cm thick layer of refrozen snow SLF_THINCRUST 20 situations of wet snow covered by a refrozen crust whose thickness is between 1 and 3 cm SLF_WET SLF: Acronym for alpine test site of Swiss Snow and  Avalanche Research Institute, Weiss-fluhjoch Davos: Lat. 48.83°N, Long. 9.81°E, Alt. 2560 m a.s.l., Ground: rocky serpentine soil. pixel size: 10 m 2  53 situations of wet snow, i.e. there was at least a wet surface layer  Mean values of ground-truth observed in each object class Object Class  dw(mm) h(cm) Tveg(C) mg(%) ρ (g/cm 3 ) Tsoil(C) ε ' soil Tsnow(C) Hsnow(cm) WE(cm) Tair(C) Teff(C) YOUNG BARLEY 1.94 47.2 11.3 30.6 1.22 11.3 22.9 0 0 11.4 11.1 YOUNG OAT 1.18 39.8 17.1 23.5 1.02 17.4 13.9 0 0 16.6 17.5 UNFROZEN GRASS 1.23 20.6 10.2 30.8 1.2 10.9 22.8 0 0 10.8 10.4 SHORT GRASS 0.71 8.9 5.9 36.1 1.21 6.6 29.4 0 0 6.1 6.2 MEDIUM GRASS 1.2 23.2 9.1 34.3 1.2 9.9 24.6 0 0 10.1 9.3 HIGH GRASS 2.23 44.1 18.1 16.8 1.18 18.7 5.4 0 0 19.9 18.3 GRASS AFTER SNOW 0.4 5 2.8 37.1 1.24 2.7 30.5 0 0 4.6 3.3 FROST GRASS 0.97 8.3 -3.7 37.8 1.23 -1.3 5.2 0.1 0.01 -2.5 -2.6 FROZEN GRASS 0.95 8.5 -3.2 44.3 1.22 -1.2 9.1 0 0 -2.7 -2.3 FROZEN SOIL 0.03 10 -4 33.3 1.15 -3.6 4.4 0.1 0.01 -5.1 -3.6 BARE SOIL 0.01 4.8 11.3 31.4 1.06 11.2 12.7 0 0 12 11.1 POWDER SNOW 0.48 7 -1.2 37.4 1.2 0 14.1 -8.4 24.1 3.65 -4.8 -1 THIN CRUST 0.4 5.8 -1.1 35 1.2 -0.2 5.2 -4.3 11 1.83 -2.4 -0.9 BOTTOM CRUST 0.75 6.5 -1.5 39.3 1.16 -0.7 -5.2 11 2.9 -1.3 -0.9 WET SNOW 0.4 8 0 35 1.2 0 0.0 14.3 3.06 2.3 0 SLF_BARE 0 0 8.4 0 0 8.4 SLF_BOTTOMCRUST 0 0 0 28.17 -3.9 SLF_DEEP 0 0 -6.6 44.94 -3.2 SLF_MEDIUM 0 0 -6 18.75 -3.2 SLF_SHALLOW 0 0 -4.1 7.32 -2 SLF_THICKCRUST 0 0 0 >10 -1.2 SLF_THINCRUST 0 0 -0.3 >10 -0.2 SLF_WET 0 0 -0.3 >10 -0.2
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