Combining satellite observations to develop a global soil moisture product for near-real-time applications

Hydrology and Earth System Sciences

Volumn 20, Issue 10, 2016, Pages 4191-4208

  Enenkel, Markus ^a,b   Reimer, Christoph ^a   Dorigo, Wouter ^a   Wagner, Wolfgang ^a   Pfeil, Isabella ^a   Parinussa, Robert ^c,d   De Jeu, Richard ^d  

^a VIENNA UNIVERSITY OF TECHNOLOGY   (Austria)

^b Earth Institute   (United States)

^c UNIVERSITY OF NEW SOUTH WALES   (Australia)

^d VanderSat BV   (Netherlands)

Author keywords

[No Author keywords available]

Indexed keywords

CLIMATE CHANGE; FLOOD CONTROL; FLOODS; METEOROLOGICAL INSTRUMENTS; MOISTURE; RADIOMETERS; SATELLITES; SOILS; WEATHER FORECASTING;

ADVANCED MICROWAVE SCANNING RADIOMETER; EUROPEAN SPACE AGENCY; GLOBAL CORRELATION; IN-SITU OBSERVATIONS; INDIVIDUAL STRENGTH; OPERATIONAL APPLICATIONS; SATELLITE OBSERVATIONS; SURFACE SOIL MOISTURE;

SOIL MOISTURE;

AMSR-E; CALIBRATION; DATA PROCESSING; DATA SET; GLOBAL PERSPECTIVE; METOP; REAL TIME; SATELLITE DATA; SCATTEROMETER; SENSOR; SOIL MOISTURE; SPATIAL RESOLUTION; UNCERTAINTY ANALYSIS;

FRANCE; KENYA; SENEGAL; SPAIN;

EID: 84992110541     PISSN: 10275606     EISSN: 16077938     Source Type: Journal    
DOI: 10.5194/hess-20-4191-2016     Document Type: Article

References (72)

1. Albergel, C., Rüdiger, C., Pellarin, T., Calvet, J.-C., Fritz, N., Froissard, F., Suquia, D., Petitpa, A., Piguet, B., Martin, E. : From near-surface to root-zone soil moisture using an exponential filter: an assessment of the method based on in-situ observations and model simulations, Hydrol. Earth Syst. Sci., 12, 1323-1337, doi:10. 5194/hess-12-1323-2008, 2008.
2. Albergel, C., de Rosnay, P., Gruhier, C., Munõz-Sabater, J., Hasenauer, S., Isaksen, L., Kerr, Y., Wagner, W. : Evaluation of remotely sensed and modelled soil moisture products using global ground-based in situ observations, Remote Sens. Environ., 118, 215-226, doi:10. 1016/j. rse. 2011. 11. 017, 2012.
3. Albergel, C., Dorigo, W., Reichle, R. H., Balsamo, G., de Rosnay, P., Munõz-Sabater, J., Isaksen, L., de Jeu, R., Wagner, W. : Skill and Global Trend Analysis of Soil Moisture from Reanalyses and Microwave Remote Sensing, J. Hydrometeorol., 14, 1259-1277, doi:10. 1175/JHM-D-12-0161. 1, 2013.
4. Al-Yaari, A., Wigneron, J.-P., Ducharne, A., Kerr, Y. H., Wagner, W., De Lannoy, G., Reichle, R., Al Bitar, A., Dorigo, W., Richaume, P., Mialon, A. : Global-scale comparison of passive (SMOS) and active (ASCAT) satellite based microwave soil moisture retrievals with soil moisture simulations (MERRA-Land), Remote Sens. Environ., 152, 614-626, doi:10. 1016/j. rse. 2014. 07. 013, 2014.
5. Anderson, W. B., Zaitchik, B. F., Hain, C. R., erson, M. C., Yilmaz, M. T., Mecikalski, J., Schultz, L. : Towards an integrated soil moisture drought monitor for East Africa, Hydrol. Earth Syst. Sci., 16, 2893-2913, doi:10. 5194/hess-16-2893-2012, 2012.
6. Barichivich, J., Briffa, K. R., Myneni, R., Schrier, G. van der, Dorigo, W., Tucker, C. J., Osborn, T. J., Melvin, T. M. : Temperature and Snow-Mediated Moisture Controls of Summer Photosynthetic Activity in Northern Terrestrial Ecosystems between 1982 and 2011, Remote Sens., 6, 1390-1431, doi:10. 3390/rs6021390, 2014.
7. Bartalis, Z., Scipal, K., Wagner, W. : Soil Moisture Products from C-Band Scatterometers: From Ers-1/2 to Metop, in: Proceedings of the 2004 ENVISAT & ERS Symposium, Salzburg, Austria, 6-10 September, 2004, ESA SP-572, European Space Agency, Noordwijk, the Netherlands, 2005.
8. Bolten, J. D. and Crow, W. T. : Improved prediction of quasiglobal vegetation conditions using remotely-sensed surface soil moisture, Geophys. Res. Lett., 39, doi:10. 1029/2012GL053470, 2012.
9. Brocca, L., Melone, F., Moramarco, T., Morbidelli, R. : Soil moisture temporal stability over experimental areas in Central Italy, Geoderma, 148, 364-374, doi:10. 1016/j. geoderma. 2008. 11. 004, 2009.
10. Brocca, L., Melone, F., Moramarco, T., Wagner, W., Naeimi, V., Bartalis, Z., Hasenauer, S. : Improving runoff prediction through the assimilation of the ASCAT soil moisture product, Hydrol. Earth Syst. Sci., 14, 1881-1893, doi:10. 5194/hess-14-1881-2010, 2010.
11. Brocca, L., Hasenauer, S., Lacava, T., Melone, F., Moramarco, T., Wagner, W., Dorigo, W., Matgen, P., Martínez-Fernández, J., Llorens, P., Latron, J., Martin, C., Bittelli, M. : Soil moisture estimation through ASCAT and AMSR-E sensors: An intercomparison and validation study across Europe, Remote Sens. Environ., 115, 3390-3408, doi:10. 1016/j. rse. 2011. 08. 003, 2011.
12. Brocca, L., Moramarco, T., Melone, F., Wagner, W. : A new method for rainfall estimation through soil moisture observations, Geophys. Res. Lett., 40, 853-858, doi:10. 1002/grl. 50173, 2013.
13. Crow, W. T., Berg, A. A., Cosh, M. H., Loew, A., Mohanty, B. P., Panciera, R., de Rosnay, P., Ryu, D., Walker, J. P. : Upscaling sparse ground-based soil moisture observations for the validation of coarse-resolution satellite soil moisture products, Rev. Geophys., 50, RG2002, doi:10. 1029/2011RG000372, 2012.
14. Dee, D. P., Uppala, S. M., Simmons, A. J., Berrisford, P., Poli, P., Kobayashi, S., rae, U., Balmaseda, M. A., Balsamo, G., Bauer, P., Bechtold, P., Beljaars, A. C. M., van de Berg, L., Bidlot, J., Bormann, N., Delsol, C., Dragani, R., Fuentes, M., Geer, A. J., Haimberger, L., Healy, S. B., Hersbach, H., Hólm, E. V., Isaksen, L., Kållberg, P., Köhler, M., Matricardi, M., McNally, A. P., Monge-Sanz, B. M., Morcrette, J.-J., Park, B.-K., Peubey, C., de Rosnay, P., Tavolato, C., Thépaut, J.-N., Vitart, F. : The ERA-Interim reanalysis: configuration and performance of the data assimilation system, Q. J. Roy. Meteor. Soc., 137, 553-597, doi:10. 1002/qj. 828, 2011.
15. de Jeu, R. A. M., Holmes, T. R. H., Parinussa, R. M., Owe, M. : A spatially coherent global soil moisture product with improved temporal resolution, J. Hydrol., 516, 284-296, doi:10. 1016/j. jhydrol. 2014. 02. 015, 2014.
16. de Nijs, A. H. A., Parinussa, R. M., de Jeu, R. A. M., Schellekens, J., Holmes, T. R. H. : A Methodology to Determine Radio-Frequency Interference in AMSR2 Observations, IEEE T. Geosci. Remote Sens., 53, 5148-5159, doi:10. 1109/TGRS. 2015. 2417653, 2015.
17. Dorigo, W. and de Jeu, R. : Satellite soil moisture for advancing our understanding of earth system processes and climate change, Int. J. Appl. Earth Obs. Geoinformation, 48, 1-4, doi:10. 1016/j. jag. 2016. 02. 007, 2016.
18. Dorigo, W., de Jeu, R., Chung, D., Parinussa, R., Liu, Y., Wagner, W., Fernández-Prieto, D. : Evaluating global trends (1988-2010) in harmonized multi-satellite surface soil moisture, Geophys. Res. Lett., 39, doi:10. 1029/2012GL052988, 2012.
19. Dorigo, W. A., Scipal, K., Parinussa, R. M., Liu, Y. Y., Wagner, W., de Jeu, R. A. M., Naeimi, V. : Error characterisation of global active and passive microwave soil moisture datasets, Hydrol. Earth Syst. Sci., 14, 2605-2616, doi:10. 5194/hess-14-2605-2010, 2010.
20. Dorigo, W. A., Wagner, W., Hohensinn, R., Hahn, S., Paulik, C., Xaver, A., Gruber, A., Drusch, M., Mecklenburg, S., van Oevelen, P., Robock, A., Jackson, T. : The International Soil Moisture Network: a data hosting facility for global in situ soil moisture measurements, Hydrol. Earth Syst. Sci., 15, 1675-1698, doi:10. 5194/hess-15-1675-2011, 2011.
21. Dorigo, W. A., Xaver, A., Vreugdenhil, M., Gruber, A., Hegyiová, A., Sanchis-Dufau, A. D., Zamojski, D., Cordes, C., Wagner, W., Drusch, M. : Global Automated Quality Control of In Situ Soil Moisture Data from the International Soil Moisture Network, Vadose Zone J., 12, doi:10. 2136/vzj2012. 0097, 2013.
22. Dorigo, W. A., Gruber, A., De Jeu, R. A. M., Wagner, W., Stacke, T., Loew, A., Albergel, C., Brocca, L., Chung, D., Parinussa, R. M., Kidd, R. : Evaluation of the ESA CCI soil moisture product using ground-based observations, Remote Sens. Environ., 162, 380-395, doi:10. 1016/j. rse. 2014. 07. 023, 2015.
23. Drusch, M. : Initializing numerical weather prediction models with satellite-derived surface soil moisture: Data assimilation experiments with ECMWF's Integrated Forecast System and the TMI soil moisture data set, J. Geophys. Res.-Atmos., 112, D03102, doi:10. 1029/2006JD007478, 2007.
24. Drusch, M., Scipal, K., de Rosnay, P., Balsamo, G., ersson, E., Bougeault, P., Viterbo, P. : Towards a Kalman Filter based soil moisture analysis system for the operational ECMWF Integrated Forecast System, Geophys. Res. Lett., 36, doi:10. 1029/2009GL037716, 2009.
25. Enenkel, M., See, L., Bonifacio, R., Boken, V., Chaney, N., Vinck, P., You, L., Dutra, E., erson, M. : Drought and food security-Improving decision-support via new technologies and innovative collaboration, Global Food Secur., 4, 51-55, doi:10. 1016/j. gfs. 2014. 08. 005, 2014.
26. Greve, P., Orlowsky, B., Mueller, B., Sheffield, J., Reichstein, M., Seneviratne, S. I. : Global assessment of trends in wetting and drying over land, Nat. Geosci., 7, 716-721, doi:10. 1038/ngeo2247, 2014.
27. Group on Earth Observations: Critical Earth Observation Priorities (Second Edition), available at: http://sbageotask. larc. nasa. gov/Final-SBA-Report-US0901a-v2. pdf (last access: 28 January 2015) 2012.
28. Gruber, A., Su, C.-H., Crow, W. T., Zwieback, S., Dorigo, W. A., Wagner, W. : Estimating error cross-correlations in soil moisture data sets using extended collocation analysis, J. Geophys. Res.-Atmos., 121, 1208-1219, doi:10. 1002/2015JD024027, 2016.
29. Gruhier, C., de Rosnay, P., Hasenauer, S., Holmes, T., de Jeu, R., Kerr, Y., Mougin, E., Njoku, E., Timouk, F., Wagner, W., Zribi, M. : Soil moisture active and passive microwave products: intercomparison and evaluation over a Sahelian site, Hydrol. Earth Syst. Sci., 14, 141-156, doi:10. 5194/hess-14-141-2010, 2010.
30. Hirschi, M., Mueller, B., Dorigo, W., Seneviratne, S. I. : Using remotely sensed soil moisture for land-atmosphere coupling diagnostics: The role of surface vs. root-zone soil moisture variability, Remote Sens. Environ., 154, 246-252, doi:10. 1016/j. rse. 2014. 08. 030, 2014.
31. Holmes, T. R. H., De Jeu, R. A. M., Owe, M., Dolman, A. J. : Land surface temperature from Ka band (37 GHz) passive microwave observations, J. Geophys. Res.-Atmos., 114, D04113, doi:10. 1029/2008JD010257, 2009.
32. Jung, M., Reichstein, M., Ciais, P., Seneviratne, S. I., Sheffield, J., Goulden, M. L., Bonan, G., Cescatti, A., Chen, J., de Jeu, R., Dolman, A. J., Eugster, W., Gerten, D., Gianelle, D., Gobron, N., Heinke, J., Kimball, J., Law, B. E., Montagnani, L., Mu, Q., Mueller, B., Oleson, K., Papale, D., Richardson, A. D., Roupsard, O., Running, S., Tomelleri, E., Viovy, N., Weber, U., Williams, C., Wood, E., Zaehle, S., Zhang, K. : Recent decline in the global land evapotranspiration trend due to limited moisture supply, Nature, 467, 951-954, doi:10. 1038/nature09396, 2010.
33. Legates, D. R., Mahmood, R., Levia, D. F., DeLiberty, T. L., Quiring, S. M., Houser, C., Nelson, F. E. : Soil moisture: A central and unifying theme in physical geography, Prog. Phys. Geogr., 35, 65-86, doi:10. 1177/0309133310386514, 2010.
34. Lei, F., Crow, W. T., Shen, H., Parinussa, R. M., Holmes, T. R. H. : The Impact of Local Acquisition Time on the Accuracy of Microwave Surface Soil Moisture Retrievals over the Contiguous United States, Remote Sens., 7, 13448-13465, doi:10. 3390/rs71013448, 2015.
35. Liu, Y. Y., van Dijk, A. I. J. M., de Jeu, R. A. M., Holmes, T. R. H. : An analysis of spatiotemporal variations of soil and vegetation moisture from a 29-year satellite-derived data set over mainland Australia, Water Resour. Res., 45, W07405, doi:10. 1029/2008WR007187, 2009.
36. Liu, Y. Y., Parinussa, R. M., Dorigo, W. A., De Jeu, R. A. M., Wagner, W., van Dijk, A. I. J. M., McCabe, M. F., Evans, J. P. : Developing an improved soil moisture dataset by blending passive and active microwave satellite-based retrievals, Hydrol. Earth Syst. Sci., 15, 425-436, doi:10. 5194/hess-15-425-2011, 2011a.
37. Liu, Y. Y., de Jeu, R. A. M., McCabe, M. F., Evans, J. P., van Dijk, A. I. J. M. : Global long-term passive microwave satellitebased retrievals of vegetation optical depth, Geophys. Res. Lett., 38, L18402, doi:10. 1029/2011GL048684, 2011b.
38. Liu, Y. Y., Dorigo, W. A., Parinussa, R. M., de Jeu, R. A. M., Wagner, W., McCabe, M. F., Evans, J. P., van Dijk, A. I. J. M. : Trend-preserving blending of passive and active microwave soil moisture retrievals, Remote Sens. Environ., 123, 280-297, doi:10. 1016/j. rse. 2012. 03. 014, 2012.
39. Liu, Y. Y., van Dijk, A. I. J. M., de Jeu, R. A. M., Canadell, J. G., McCabe, M. F., Evans, J. P., Wang, G. : Recent reversal in loss of global terrestrial biomass, Nat. Clim. Change, 5, 470-474, doi:10. 1038/nclimate2581, 2015.
40. McNally, A., Husak, G. J., Brown, M., Carroll, M., Funk, C., Yatheendradas, S., Arsenault, K., Peters-Lidard, C., Verdin, J. P. : Calculating Crop Water Requirement Satisfaction in the West Africa Sahel with Remotely Sensed Soil Moisture, J. Hydrometeorol., 16, 295-305, doi:10. 1175/JHM-D-14-0049. 1, 2015.
41. Mistelbauer, T., Enenkel, M., Wagner, W. : POETS-Python Earth Observation Tools, Poster: GIScience 2014, Vienna, 23 September 2014, in: "Extended Abstract Proceedings of the GIScience 2014", GeoInfo Series, 40, 2014.
42. Munõz, A. A., Barichivich, J., Christie, D. A., Dorigo, W., Sauchyn, D., González-Reyes, Á., Villalba, R., Lara, A., Riquelme, N., González, M. E. : Patterns and drivers of Araucaria araucana forest growth along a biophysical gradient in the northern Patagonian Andes: Linking tree rings with satellite observations of soil moisture, Austral. Ecol., 39, 158-169, doi:10. 1111/aec. 12054, 2014.
43. Nicolai-Shaw, N., Hirschi, M., Mittelbach, H., Seneviratne, S. I. : Spatial representativeness of soil moisture using in situ, remote sensing, land reanalysis data: SPATIAL REPRESENTATIVENESS OF SOIL MOISTURE, J. Geophys. Res.-Atmos., 120, 9955-9964, doi:10. 1002/2015JD023305, 2015.
44. Njoku, E. G. and Li, L. : Retrieval of land surface parameters using passive microwave measurements at 6-18 GHz, IEEE T. Geosci. Remote Sens., 37, 79-93, doi:10. 1109/36. 739125, 1999.
45. Okuyama, A. and Imaoka, K. : Intercalibration of Advanced Microwave Scanning Radiometer-2 (AMSR2) Brightness Temperature, IEEE T. Geosci. Remote Sens., 53, 4568-4577, doi:10. 1109/TGRS. 2015. 2402204, 2015.
46. Oliva, R., Daganzo, E., Kerr, Y. H., Mecklenburg, S., Nieto, S., Richaume, P., Gruhier, C. : SMOS Radio Frequency Interference Scenario: Status and Actions Taken to Improve the RFI Environment in the 1400 #x2013;1427-MHz Passive Band, IEEE T. Geosci. Remote Sens., 50, 1427-1439, doi:10. 1109/TGRS. 2012. 2182775, 2012.
47. Owe, M., de Jeu, R., Holmes, T. : Multisensor historical climatology of satellite-derived global land surface moisture, J. Geophys. Res.-Earth, 113, F01002, doi:10. 1029/2007JF000769, 2008.
48. Parinussa, R. M., Holmes, T. R. H., Wanders, N., Dorigo, W. A., de Jeu, R. A. M. : A Preliminary Study toward Consistent Soil Moisture from AMSR2, J. Hydrometeorol., 16, 932-947, doi:10. 1175/JHM-D-13-0200. 1, 2015.
49. Qiu, J., Crow, W. T., Nearing, G. S., Mo, X., Liu, S. : The impact of vertical measurement depth on the information content of soil moisture times series data, Geophys. Res. Lett., 41, 4997-5004, doi:10. 1002/2014GL060017, 2014.
50. Reichle, R. H. and Koster, R. D. : Bias reduction in short records of satellite soil moisture, Geophys. Res. Lett., 31, L19501, doi:10. 1029/2004GL020938, 2004.
51. Reichle, R. H., Koster, R. D., Dong, J., Berg, A. A. : Global Soil Moisture from Satellite Observations, Land Surface Models, Ground Data: Implications for Data Assimilation, J. Hydrometeorol., 5, 430-442, doi:10. 1175/1525-7541(2004)0050430:GSMFSO2. 0. CO;2, 2004.
52. Rodell, M., Houser, P. R., Jambor, U., Gottschalck, J., Mitchell, K., Meng, C.-J., Arsenault, K., Cosgrove, B., Radakovich, J., Bosilovich, M., Entin, J. K., Walker, J. P., Lohmann, D., Toll, D. : The Global Land Data Assimilation System, B. Am. Meteor. Soc., 85, 381-394, doi:10. 1175/BAMS-85-3-381, 2004.
53. Rüdiger, C., Calvet, J.-C., Gruhier, C., Holmes, T. R. H., de Jeu, R. A. M., Wagner, W. : An Intercomparison of ERSScat and AMSR-E Soil Moisture Observations with Model Simulations over France, J. Hydrometeorol., 10, 431-447, doi:10. 1175/2008JHM997. 1, 2009.
54. Sanchez, N., Martinez-Fernandez, J., Scaini, A., Perez-Gutierrez, C. : Validation of the SMOS L2 Soil Moisture Data in the REMEDHUS Network (Spain), IEEE T. Geosci. Remote Sens., 50, 1602-1611, doi:10. 1109/TGRS. 2012. 2186971, 2012.
55. Schmugge, T. and Jackson, T. J. : Mapping surface soil moisture with microwave radiometers, Meteorol. Atmos. Phys., 54, 213-223, doi:10. 1007/BF01030061, 1994.
56. Scipal, K., Drusch, M., Wagner, W. : Assimilation of a ERS scatterometer derived soil moisture index in the ECMWF numerical weather prediction system, Adv. Water Resour., 31, 1101-1112, doi:10. 1016/j. advwatres. 2008. 04. 013, 2008.
57. Seneviratne, S. I., Corti, T., Davin, E. L., Hirschi, M., Jaeger, E. B., Lehner, I., Orlowsky, B., Teuling, A. J. : Investigating soil moisture-climate interactions in a changing climate: A review, Earth Sci. Rev., 99, 125-161, doi:10. 1016/j. earscirev. 2010. 02. 004, 2010.
58. Sheffield, J. and Wood, E. F. : Global Trends and Variability in Soil Moisture and Drought Characteristics, 1950-2000, from Observation-Driven Simulations of the Terrestrial Hydrologic Cycle, J. Clim., 21, 432-458, doi:10. 1175/2007JCLI1822. 1, 2008.
59. Taylor, C. M., de Jeu, R. A. M., Guichard, F., Harris, P. P., Dorigo, W. A. : Afternoon rain more likely over drier soils, Nature, 489, 423-426, doi:10. 1038/nature11377, 2012.
60. Taylor, K. E. : Summarizing multiple aspects of model performance in a single diagram, J. Geophys. Res.-Atmos., 106, 7183-7192, doi:10. 1029/2000JD900719, 2001.
61. Trenberth, K. E., Dai, A., van der Schrier, G., Jones, P. D., Barichivich, J., Briffa, K. R., Sheffield, J. : Global warming and changes in drought, Nat. Clim. Change, 4, 17-22, doi:10. 1038/nclimate2067, 2014.
62. Vachaud, G., Passerat De Silans, A., Balabanis, P., Vauclin, M. : Temporal Stability of Spatially Measured Soil Water Probability Density Function, Soil Sci. Soc. Am. J., 49, 822-828, doi:10. 2136/sssaj1985. 03615995004900040006x, 1985.
63. Wagner, W., Lemoine, G., Rott, H. : A Method for Estimating Soil Moisture from ERS Scatterometer and Soil Data, Remote Sens. Environ., 70, 191-207, doi:10. 1016/S0034-4257(99)00036-X, 1999.
64. Wagner, W., Scipal, K., Pathe, C., Gerten, D., Lucht, W., Rudolf, B. : Evaluation of the agreement between the first global remotely sensed soil moisture data with model and precipitation data, J. Geophys. Res.-Atmos., 108, doi:10. 1029/2003JD003663, 2003.
65. Wagner, W., Blöschl, G., Pampaloni, P., Calvet, J. C., Bizzarri, B., Wigneron, J. P., Kerr, Y. : Operational readiness of microwave remote sensing of soil moisture for hydrologic applications, Nord. Hydrol., 38, 1-20, 2007.
66. Wagner, W., Dorigo, W., de Jeu, R., Fernandez, D., Benveniste, J., Haas, E., Ertl, M. : Fusion of active and passive microwave observations to create an essential climate variable data record on soil moisture, ISPRS Ann. Photogramm. Remote Sens. Spat. Inf. Sci., I-7, 315-321, doi:10. 5194/isprsannals-I-7-315-2012, 2012.
67. Wagner, W., Hahn, S., Kidd, R., Melzer, T., Bartalis, Z., Hasenauer, S., Figa-Saldanã, J., de Rosnay, P., Jann, A., Schneider, S., Komma, J., Kubu, G., Brugger, K., Aubrecht, C., Züger, J., Gangkofner, U., Kienberger, S., Brocca, L., Wang, Y., Blöschl, G., Eitzinger, J., Steinnocher, K., Zeil, P., Rubel, F. : The ASCAT Soil Moisture Product: A Review of its Specifications, Validation Results, Emerging Applications, Meteorol. Z., 22, 5-33, doi:10. 1127/0941-2948/2013/0399, 2013.
68. Wang, J. R. and Schmugge, T. J. : An Empirical Model for the Complex Dielectric Permittivity of Soils as a Function of Water Content, IEEE T. Geosci. Remote Sens., GE-18, 288-295, doi:10. 1109/TGRS. 1980. 350304, 1980.
69. Western, A. W., Grayson, R. B., Blöschl, G. : SCALING OF SOIL MOISTURE: A Hydrologic Perspective, Annu. Rev. Earth Planet. Sci., 30, 149-180, doi:10. 1146/annurev. earth. 30. 091201. 140434, 2002.
70. World Meteorological Organization: Future Climate Change Research and Observations: GCOS, WCRP and IGBP Learning from the IPCC Fourth Assessment Report, WMO/TD 1418, GCOS-117, WCRP-127, IGBP Report 58, Geneva, World Meteorological Organization, 2008.
71. World Meteorological Organization: Sentinel High Level Operations Plan (HLOP), available at: https://www. wmo. int/pages/prog/sat/meetings/documents/PSTG-3-Doc-08-04-02-Sentinel-HLOP. pdf, (last access: 24 June 2015), 2013.
72. Yuan, X., Ma, Z., Pan, M., Shi, C. : Microwave remote sensing of short-term droughts during crop growing seasons: REMOTE SENSING OF SHORT-TERM DROUGHTS, Geophys. Res. Lett., 42, 4394-4401, doi:10. 1002/2015GL064125, 2015.