Spatio-temporal variability of droughts and terrestrial water storage over Lake Chad Basin using independent component analysis

Journal of Hydrology

Volumn 540, Issue , 2016, Pages 106-128

  Ndehedehe, Christopher E ^a   Agutu, Nathan O ^a,b   Okwuashi, Onuwa ^c   Ferreira, Vagner G ^d  

^a CURTIN UNIVERSITY   (Australia)

^b JKUAT   (Kenya)

^c UNIVERSITY OF UYO   (Nigeria)

^d HOHAI UNIVERSITY   (China)

Author keywords

Drought; ICA; Rainfall; Soil moisture; SPI; TWS

Indexed keywords

ATMOSPHERIC PRESSURE; CATCHMENTS; CLIMATOLOGY; DIGITAL STORAGE; GEODETIC SATELLITES; INDEPENDENT COMPONENT ANALYSIS; LAKES; MOISTURE; RAIN; SOIL MOISTURE; SOILS; WATER LEVELS;

GRAVITY RECOVERY AND CLIMATE EXPERIMENTS; INDEPENDENT COMPONENT ANALYSIS(ICA); SATELLITE ALTIMETRY DATA; SPATIAL AND TEMPORAL PATTERNS; SPATIO-TEMPORAL APPROACH; SPATIOTEMPORAL VARIABILITY; TELECONNECTION INDICES; TERRESTRIAL WATER STORAGE;

DROUGHT;

ATLANTIC MULTIDECADAL OSCILLATION; CATCHMENT; CLIMATE CONDITIONS; DROUGHT; EL NINO-SOUTHERN OSCILLATION; GRACE; HUMAN ACTIVITY; PRINCIPAL COMPONENT ANALYSIS; RAINFALL; SATELLITE ALTIMETRY; SOIL MOISTURE; SPATIAL VARIATION; TEMPORAL EVOLUTION; TEMPORAL VARIATION; WATER LEVEL; WATER STORAGE;

CHAD BASIN; LAKE CHAD;

EID: 84975466267     PISSN: 00221694     EISSN: None     Source Type: Journal    
DOI: 10.1016/j.jhydrol.2016.05.068     Document Type: Article

References (96)

1. Adler, R.F., Huffman, G.J., Chang, A., Ferraro, R., Xie, P.-P., Janowiak, J., Rudolf, B., Schneider, U., Curtis, S., Bolvin, D., Gruber, A., Susskind, J., Arkin, P., Nelkin, E., The version-2 Global Precipitation Climatology Project (GPCP) monthly precipitation analysis (1979Present). J. Hydrometeorol. 4:6 (2003), 1147–1167, 10.1175/1525-7541(2003)004<1147:TVGPCP>2.0.CO;2.
2. AghaKouchak, A., A multivariate approach for persistence-based drought prediction: application to the 2010–2011 East Africa drought. J. Hydrol. 526 (2015), 127–135, 10.1016/j.jhydrol.2014.09.063.
3. Aires, F., Rossow, W.B., ChéDin, A., Rotation of EOFs by the independent component analysis: toward a solution of the mixing problem in the decomposition of geophysical time series. J. Atmos. Sci. 59 (2002), 111–123, 10.1175/1520-0469(2002)059<0111:ROEBTI>2.0.CO;2.
4. Alfa, N.I., Adeofun, C.O., Ologunorisa, E.T., Assessment of changes in aerial extent of Lake Chad using satellite remote sensing data. J. Appl. Sci. Environ. Manage. 12:1 (2008), 101–107.
5. Ali, A., Lebel, T., The Sahelian standardized rainfall index revisited. Int. J. Climatol. 29 (2009), 1705–1714, 10.1002/joc.1832.
6. Bader, J., Latif, M., The 1983 drought in the West Sahel: a case study. Clim. Dyn. 36:3–4 (2011), 463–472, 10.1007/s00382-009-0700-y.
7. Ball, G.H., Hall, D.J., 1965. Isodata, a novel method of data analysis and pattern classification. Technical Report. Stanford Research Institute, Menlo Park, California. Retrieved from: < http://oai.dtic.mil/oai/oai?verb=getRecord&metadataPrefix=html&identifier=AD0699616> (accessed 25 March, 2016).
8. Baup, F., Frappart, F., Maubant, J., Combining high-resolution satellite images and altimetry to estimate the volume of small lakes. Hydrol. Earth Syst. Sci. 18:5 (2014), 2007–2020, 10.5194/hess-18-2007-2014.
9. Baur, O., Kuhn, M., Featherstone, W.E., GRACE-derived ice-mass variations over Greenland by accounting for leakage effects. J. Geophys. Res.: Solid Earth, 114(B6), 2009, B06407, 10.1029/2008JB006239.
10. Bazrafshan, J., Hejabi, S., Rahimi, J., Drought monitoring using the multivariate standardized precipitation index (MSPI). Water Resour. Manage. 28 (2014), 1045–1060, 10.1007/s11269-014-0533-2.
11. Bekoe, E.O., Logah, F.Y., The impact of droughts and climate change on electricity generation in Ghana. Environ. Sci. 1:1 (2013), 13–24.
12. Belda, S., García-García, D., Ferrándiz, J.M., On the decorrelation filtering of RL05 GRACE data for global applications. Geophys. J. Int. 200 (2015), 173–184, 10.1093/gji/ggu386.
13. Birkett, C.M., Synergistic remote sensing of Lake Chad: variability of basin inundation. Remote Sens. Environ., 72(218236), 2000.
14. Boergens, E., Rangelova, E., Sideris, M.G., Kusche, J., Assessment of the capabilities of the temporal and spatiotemporal ICA method for geophysical signal separation in GRACE data. J. Geophys. Res. Solid Earth 119 (2014), 4429–4447, 10.1002/2013JB010452.
15. Bonaccorso, B., Bordi, I., Cancelliere, A., Rossi, G., Sutera, A., Spatial variability of drought: an analysis of the SPI in Sicily. Water Resour. Manage. 17:4 (2003), 273–296, 10.1023/A:1024716530289.
16. Cardoso, J.-F., 1991. Super-symmetric decomposition of the fourth-order cumulant tensor, blind identification of more sources than sensors. Retrieved from: < http://perso.telecom-paristech.fr/cardoso/Papers.PDF/icassp91.pdf> (accessed 15.01.16).
17. Cardoso, J.F., High-order contrasts for independent component analysis. Neural Comput. 11 (1999), 157–192.
18. Cardoso, J.F., Souloumiac, A., Blind beamforming for non-gaussian signals. IEE Proc. 140:6 (1993), 362–370.
19. Cheng, M.K., Tapley, B.D., Ries, J.C., Deceleration in the Earth's oblateness. J. Geophys. Res. 118 (2013), 1–8, 10.1002/jgrb.50058.
20. Coe, M.T., Birkett, C.M., Calculation of river discharge and prediction of lake height from satellite radar altimetry: example for the Lake Chad basin. Water Resour. Res., 40(10), 2004, W10205, 10.1029/2003WR002543.
21. Coe, M.T., Foley, J.A., Human and natural impacts on the water resources of the Lake Chad basin. J. Geophys. Res. 106:4 (2001), 3349–3356, 10.1029/2000JD900587.
22. Common, P., Independent component analysis, a new concept?. Signal Process. 36 (1994), 287–314.
23. Descroix, L., Mahé, G., Lebel, T., Favreau, G., Galle, S., Gautier, E., Olivry, J.-C., Albergel, J., Amogu, O., Cappelaere, B., Dessouassi, R., Diedhiou, A., Breton, E.L., Mamadou, I., Sighomnou, D., Spatio-temporal variability of hydrological regimes around the boundaries between Sahelian and Sudanian areas of West Africa: a synthesis. J. Hydrol. 375:12 (2009), 90–102, 10.1016/j.jhydrol.2008.12.012.
24. Diatta, S., Fink, A.H., Statistical relationship between remote climate indices and West African monsoon variability. Int. J. Climatol. 34:12 (2014), 3348–3367, 10.1002/joc.3912.
25. Dirmeyer, P.A., Guo, Z., Gao, X., Comparison, validation, and transferability of eight multiyear global soil wetness products. J. Hydrometeorol. 5 (2004), 1011–1033, 10.1175/JHM-388.1.
26. Duan, Z., Bastiaanssen, W.G.M., Estimating water volume variations in lakes and reservoirs from four operational satellite altimetry databases and satellite imagery data. Remote Sens. Environ. 134 (2013), 403–416, 10.1016/j.rse.2013.03.010.
27. Duan, Z., Bastiaanssen, W.G.M., First results from version 7 TRMM 3B43 precipitation product in combination with a new downscaling calibration procedure. Remote Sens. Environ. 131 (2013), 1–13, 10.1016/j.rse.2012.12.002.
28. Fan, Y., Dool, H.V., Climate prediction center global monthly soil moisture data set at 0.5° resolution for 1948 to present. J. Geophys. Res., 109, 2004, D10102, 10.1029/2003JD004345.
29. FAO, 1997. Irrigation potential in Africa: a basin approach. FAO Land and Water Bulletin, 4. Retrieved from: < https://books.google.com.au/books> (accessed 28.09.15).
30. Farahmand, A., AghaKouchak, A., A generalized framework for deriving nonparametric standardized drought indicators. Adv. Water Resour.(76), 2015, 140–145, 10.1016/j.advwatres.2014.11.012.
31. Forootan, E., Kusche, J., Separation of global time-variable gravity signals into maximally independent components. J. Geodesy 86:7 (2012), 477–497, 10.1007/s00190-011-0532-5.
32. Frappart, F., Ramillien, G., Leblanc, M., Tweed, S.O., Bonnet, M.-P., Maisongrande, P., An independent component analysis filtering approach for estimating continental hydrology in the GRACE gravity data. Remote Sens. Environ. 115:1 (2011), 187–204, 10.1016/j.rse.2010.08.017.
33. Frappart, F., Ramillien, G., Maisongrande, P., Bonnet, M.-P., Denoising satellite gravity signals by independent component analysis. IEEE Geosci. Remote Sens. Lett. 7:3 (2010), 421–425, 10.1109/LGRS.2009.2037837.
34. Gbuyiro, S.O., Ojo, O., Iso, M., Okoloye, C., Idowu, O., 2001. Climate and water resources management. In: WEDC Conference Zambia, vol. 27, pp. 383–386. Retrieved from: < www.wedc.lboro.ac.uk/resources/conference/27/Gbuyiro.pdf> (accessed 15.05.15).
35. Giannini, A., Salack, S., Lodoun, T., Ali, A., Gaye, A., Ndiaye, O., A unifying view of climate change in the Sahel linking intra-seasonal, interannual and longer time scales. Environ. Res. Lett. 8 (2013), 1–8, 10.1088/1748-9326/8/2/024010.
36. Giannini, A., Saravanan, R., Chang, P., Oceanic forcing of Sahel rainfall on interannual to decadal time scales. Science 302:5647 (2003), 1027–1030, 10.1126/science.1089357.
37. Gosset, M., Viarre, J., Quantin, G., Alcoba, M., Evaluation of several rainfall products used for hydrological applications over West Africa using two high-resolution gauge networks. Quart. J. Roy. Meteorol. Soc. 139 (2013), 923–940, 10.1002/qj.2130.
38. Greve, P., Orlowsky, B., Mueller, B., Sheffield, J., Reichstein, M., Seneviratne, S.L., Global assessment of trends in wetting and drying over land. Nat. Geosci. 7 (2014), 716–721, 10.1038/NGE02247.
39. Grippa, M., Kergoat, L., Frappart, F., Araud, Q., Boone, A., de Rosnay, P., Lemoine, J.M., Gascoin, S., Balsamo, G., Ottl, C., Decharme, B., Saux-Picart, S., Ramillien, G., Land water storage variability over West Africa estimated by Gravity Recovery and Climate Experiment (GRACE) and land surface models. Water Resour. Res., 47(5), 2011, W05549, 10.1029/2009wr008856.
40. Hao, Z., AghaKouchak, A., Multivariate standardized drought index: a parametric multi-index model. Adv. Water Resour.(57), 2013, 12–18, 10.1016/j.advwatres.2013.03.009.
41. Hao, Z., AghaKouchak, A., A nonparametric multivariate multi-index drought monitoring framework. J. Hydrometeorol. 15:1 (2014), 89–101, 10.1175/JHM-D-12-0160.1.
42. Hayes, M.J., Svoboda, M.D., Wilhite, D.A., Vanyarkho, O.V., Monitoring the 1996 drought using the standardized precipitation index. Bull. Am. Meteorol. Soc. 80 (1999), 429–438, 10.1175/1520-0477(1999)080<0429:MTDUTS>2.0.CO;2.
43. Hinderer, J., de Linage, C., Boya, J.-P., Gegout, P., Masson, F., Rogister, Y., Amalvict, M., Pfeffer, J., Littel, F., Luck, B., Bayerb, R., Champollion, C., Collard, P., Moigne, N.L., Diamentc, M., Deroussi, S., de Viron, O., Biancale, R., Lemoine, J.-M., Bonvalot, S., Gabalda, G., Bock, O., Genthon, P., Boucher, M., Favreau, G., Sguis, L., Delclaux, F., Cappelaere, B., Oi, M., Descloitresh, M., Galleh, S., Laurent, J.-P., Legchenko, A., Bouink, M.-N., The GHYRAF (Gravity and Hydrology in Africa) experiment: description and first results. J. Geodyn. 48 (2009), 172–181, 10.1016/j.jog.2009.09.014.
44. Huang, S., Huang, Q., Chang, J., Zhu, Y., Leng, G., Xing, L., Drought structure based on a nonparametric multivariate standardized drought index across the Yellow River basin, China. J. Hydrol. 530 (2015), 127–136, 10.1016/j.jhydrol.2015.09.042.
45. Huffman, G.J., Adler, R.F., Bolvin, D.T., Gu, G., Improving the global precipitation record: GPCP version 2.1. Geophys. Res. Lett., 36(17), 2009, L17808, 10.1029/2009GL040000.
46. Huffman, G.J., Adler, R.F., Bolvin, D.T., Gu, G., Nelkin, E.J., Bowman, K.P., Hong, Y., Stocker, E.F., Wolff, D.B., The TRMM Multisatellite Precipitation Analysis (TMPA): quasi-global, multiyear, combined-sensor precipitation estimates at fine scales. J. Hydrometeorol. 8 (2007), 38–55, 10.1175/JHM560.1.
47. Inogwabini, B.-I., Sandokan, B.M., Ndunda, M., A dramatic decline in rainfall regime in the Congo Basin: evidence from a thirty four-year data set from the Mabali scientific research centre, Democratic Republic Of Congo. Int. J. Meteorol. 31:312 (2006), 278–285.
48. Jolliffe, I.T., Principal component analysis, second ed. Springer Series in Statistics, 2002, Springer, New York.
49. Komuscu, A.U., Using the SPI to analyze spatial and temporal patterns of drought in Turkey. Drought Network News 11:1 (1999), 7–13.
50. Kummerow, C., Simpson, J., Thiele, O., Barnes, W., Chang, A.T.C., Stocker, E., Adler, R.F., Hou, A., Kakar, R., Wentz, F., Ashcroft, P., Kozu, T., Hong, Y., Okamoto, K., Iguchi, T., Kuroiwa, H., Im, E., Haddad, Z., Huffman, G., Ferrier, B., Olson, W.S., Zipser, E., Smith, E.A., Wilheit, T.T., North, G., Krishnamurti, T., Nakamura, K., The status of the Tropical Rainfall Measuring Mission (TRMM) after two years in orbit. J. Appl. Meteorol. 39:12 (2000), 1965–1982, 10.1175/1520-0450(2001)040<1965:TSOTTR>2.0.CO;2.
51. Kusche, J., Approximate decorrelation and non-isotropic smoothing of time-variable GRACE-type gravity field models. J. Geodesy 81:11 (2007), 733–749, 10.1007/s00190-007-0143-3.
52. Landerer, F.W., Swenson, S.C., Accuracy of scaled GRACE terrestrial water storage estimates. Water Resour. Res., 48(4), 2012, W04531, 10.1029/2011WR011453.
53. Lebel, T., Ali, A., A physical basis for the interannual variability of rainfall in the Sahel. Quart. J. Roy. Meteorol. Soc., 375(1–2), 2009, 5264, 10.1016/j.jhydrol.2008.11.030.
54. Lebel, T., Cappelaere, B., Galle, S., Hanan, N., Kergoat, L., Levis, S., Vieux, B., Descroix, L., Gosset, M., Mougin, E., Peugeot, C., Seguis, L., AMMA-CATCH studies in the Sahelian region of West-Africa: an overview. J. Hydrol. 375:12 (2009), 3–13.
55. Leblanc, M., Leduc, C., Razack, M., Lemoalle, J., Dagorne, D., Mofor, L., Applications of remote sensing and GIS for groundwater modelling of large semiarid areas: example of the Lake Chad Basin, Africa. Hydrol. Mediterr. Semiarid Regions(278), 2003, 186–191 proceedings of the international symposium held at Montpellier, April 2003.
56. Lemoalle, J., Bader, J.-C., Leblanc, M., Sedick, A., Recent changes in Lake Chad: observations, simulations and management options (19732011). Global Planet. Change 8081 (2012), 247–254, 10.1016/j.gloplacha.2011.07.004.
57. Li, B., Rodell, M., Evaluation of a model-based groundwater drought indicator in the conterminous U.S. J. Hydrol. 526 (2015), 78–88, 10.1016/j.jhydrol.2014.09.027.
58. Lloyd-Hughes, B., A spatio-temporal structure-based approach to drought characterisation. Int. J. Climatol. 32:3 (2012), 406–418, 10.1002/joc.2280.
59. Long, D., Longuevergne, L., Scanlon, B.R., Global analysis of approaches for deriving total water storage changes from GRACE satellites. Water Resour. Res. 51:4 (2015), 2574–2594, 10.1002/2014WR016853.
60. Loon, A.F.V., Hydrological drought explained. WIREs Water 2 (2015), 359–392, 10.1002/wat2.1085.
61. Lopez, T., Antoine, R., Kerr, Y., Darrozes, J., Rabinowicz, M., Ramillien, G., Cazenave, A., Genthon, P., Subsurface hydrology of the Lake Chad Basin from convection modelling and observations. Surv. Geophys. 37:2 (2016), 471–502, 10.1007/s10712-016-9363-5.
62. Masih, I., Maskey, S., Mussá, F.E.F., Trambauer, P., A review of droughts on the African continent: a geospatial and long-term perspective. Hydrol. Earth Syst. Sci. 18:9 (2014), 3635–3649, 10.5194/hess-18-3635-2014.
63. McKee, T.B., Doeskin, N.J., Kieist, J., 1993. The relationship of drought frequency and duration to time scales. In: Conference on Applied Climatology, American Meteorological Society, Boston, Massachusetts, pp. 179–184. Retrieved from: < www.ccc.atmos.colostate.edu/relationshipofdroughtfrequency.pdf> (accessed 27.06.14).
64. Mohino, E., Rodrguez-Fonseca, B., Losada, T., Gervois, S., Janicot, S., Bader, J., Ruti, P., Chauvin, F., Changes in the interannual SST-forced signals on West African rainfall. AGCM intercomparison. Clim. Dyn. 37:9–10 (2011), 1707–1725, 10.1007/s00382-011-1093-2.
65. Moore, P., Williams, S.D.P., Integration of altimetry lake levels and GRACE gravimetry over Africa: Inferences for terrestrial water storage change 2003–2011. Water Resour. Res. 50 (2014), 9696–9720, 10.1002/2014WR015506.
66. Ndehedehe, C.E., Awange, J., Agutu, N., Kuhn, M., Heck, B., Understanding changes in terrestrial water storage over West Africa between 2002 and 2014. Adv. Water Resour. 88 (2016), 211–230, 10.1016/j.advwatres.2015.12.009.
67. Ndehedehe, C.E., Awange, J.L., Corner, R., Kuhn, M., Okwuashi, O., On the potentials of multiple climate variables in assessing the spatio-temporal characteristics of hydrological droughts over the Volta Basin. Sci. Total Environ., 2016, 819–837, 10.1016/j.scitotenv.2016.03.004.
68. Nicholson, S., The West African Sahel: a review of recent studies on the rainfall regime and its interannual variability. ISRN Meteorol. 2013:453521 (2013), 1–32, 10.1155/2013/453521.
69. Nicholson, S.E., Some, B., Kone, B., An analysis of recent rainfall conditions in West Africa, including the rainy seasons of the 1997 El Nin¨o and the 1998 La Nia Years. J. Clim. 13:14 (2000), 2628–2640, 10.1175/1520-0442(2000)013<2628:AAORRC>2.0.CO;2.
70. Odada, E.O., Oyebande, L., Oguntola, J.A., 2005. Lake Chad. Experience and Lessons Learned Briefed, pp. 75–91. Retrieved from: < www.worldlakes.org/uploads/06-Lake-Chad-27February2006.pdf> (accessed 05.10.15).
71. Okonkwo, C., Demoz, B., Gebremariam, S., Characteristics of Lake Chad level variability and links to ENSO, precipitate, and river discharge. Sci. World J., 13(4), 2014, 13, 10.1155/2014/145893.
72. Okonkwo, C., Demoz, B., Onyeukwu, K., Characteristics of drought indices and rainfall in Lake Chad Basin. Int. J. Remote Sens. 34:22 (2013), 7945–7961, 10.1080/01431161.2013.827813.
73. Paeth, H., Fink, A., Pohle, S., Keis, F., Machel, H., Samimi, C., Meteorological characteristics and potential causes of the 2007 flood in sub-Saharan Africa. Int. J. Climatol. 31 (2012), 1908–1926, 10.1002/Joc.2199.
74. Reager, J.T., Thomas, B.F., Famiglietti, J.S., River basin flood potential inferred using GRACE gravity observations at several months lead time. Nat. Geosci. 7:8 (2014), 588–592, 10.1038/ngeo2203.
75. Reynolds, R.W., Rayne, N.A., Smith, T.M., Stokes, D.C., Wang, W., An improved in situ and satellite SST analysis for climate. J. Clim. 15:3 (2002), 1609–1625, 10.1175/1520-0442(2002)0153C1609:AIISAS3E2.0.CO;2.
76. Rodell, M., Houser, P.R., Jambor, U., Gottschalck, J., Mitchell, K., Meng, K., Arsenault, C.J., Cosgrove, B., Radakovich, J., Bosilovich, M., Entin, J.K., Walker, J.P., Lohmann, D., Toll, D., The global land data assimilation system. Bull. Am. Meteorol. Soc. 85:3 (2004), 381–394, 10.1175/BAMS-85-3-381.R.
77. Rodrguez-Fonseca, B., Janicot, S., Mohino, E., Losada, T., Bader, J., Caminade, C., Chauvin, F., Fontaine, B., Garca-Serrano, J., Gervois, S., Joly, M., Polo, I., Ruti, P., Roucou, P., Voldoire, A., Interannual and decadal SST-forced responses of the West African monsoon. Atmos. Sci. Lett. 12 (2011), 67–74, 10.1002/asl.308.
78. Rouault, M., Richard, Y., Intensity and spatial extension of drought in South Africa at different time scales. Water SA 29:4 (2003), 489–500.
79. Santos, J.a.F., Pulido-Calvo, I., Portela, M.M., Spatial and temporal variability of droughts in Portugal. Water Resour. Res., 46(3), 2010, W03503, 10.1029/2009WR008071.
80. Schewe, J., Heinke, J., Gerten, D., Haddeland, I., Arnell, N.W., Clark, D.B., Dankers, R., Eisner, S., Fekete, B.M., Colón-Gonzlez, F.J., Gosling, S.N., Kim, H., Liu, X., Masaki, Y., Portmann, F.T., Satoh, Y., Stacke, T., Tang, Q., Wada, Y., Wisser, D., Albrecht, T., Frieler, K., Piontek, F., Warszawski, L., Kabat, P., Multimodel assessment of water scarcity under climate change. PNAS 111:9 (2013), 3245–3250, 10.1073/pnas.1222460110.
81. Shukla, S., Wood, A.W., Use of a standardized runoff index for characterizing hydrologic drought. Geophys. Res. Lett., 35(2), 2008, L02405, 10.1029/2007GL032487.
82. Svoboda, M., Hayes, M., Wood, D., 2012. Standardized precipitation index user guide. World Meteorological Organization, WMO-No 1090, Geneva. Retrieved from: < http://www.wamis.org/agm/pubs/SPI/WMO-1090-EN.pdf> (accessed 13.04.16).
83. Swenson, S., Chambers, D., Wahr, J., Estimating geocenter variations from a combination of GRACE and ocean model output. Geophys. Res. Lett. 31 (2008), 1–4, 10.1029/ 2004GL019920.
84. Swenson, S., Wahr, J., Methods for inferring regional surface-mass anomalies from Gravity Recovery and Climate Experiment (GRACE) measurements of time-variable gravity. J. Geophys. Res.-Solid Earth, 107(B9), 2002, 10.1029/2001jb000576.
85. Tapley, B., Bettadpur, S., Watkins, M., Reigber, C., The gravity recovery and climate experiment: mission overview and early results. Geophys. Res. Lett. 31 (2004), 1–4, 10.1029/ 2004GL019920.
86. Theis, F.J., Gruber, P., Keck, I.R., Meyer-bse, A., Lang, E.W., Spatiotemporal blind source separation using double-sided approximate joint diagonalization. In Proc. EUSIPCO 2005, 2005.
87. Tourian, M., Elmi, O., Chen, Q., Devaraju, B., Roohi, S., Sneeuw, N., A spaceborne multisensor approach to monitor the desiccation of Lake Urmia in Iran. Remote Sens. Environ. 156 (2015), 349–360, 10.1016/j.rse.2014.10.006.
88. Vassolo, S., 2012. Groundwater need assessment Lake Chad Basin. Institute for Geosciences and Natural Resources. Retrieved from: (accessed 03.11.15).
89. Vicente-Serrano, S.M., Spatial and temporal analysis of droughts in the Iberian Peninsula (19102000). Hydrol. Sci. J. 51:1 (2006), 83–97, 10.1623/hysj.51.1.83.
90. Wahr, J., Molenaar, M., Bryan, F., Time variability of the Earth's gravity field: hydrological and oceanic effects and their possible detection using GRACE. J. Geophys. Res.-Solid Earth 103:B12 (1998), 30205–30229, 10.1029/98jb02844.
91. Wald, L., Monitoring the decrease of Lake Chad from space. Geocarto Int. 5:3 (1990), 31–36, 10.1080/10106049009354266.
92. Werth, S., Gntner, A., Schmidt, R., Kusche, J., Evaluation of GRACE filter tools from a hydrological perspective. Geophys. J. Int. 179:3 (2009), 1499–1515.
93. Wouters, B., Bonin, J.A., Chambers, D.P., Riva, R.E.M., Sasgen, I., Wahr, J., GRACE, time-varying gravity, earth system dynamics and climate change. Rep. Prog. Phys., 77(11), 2014, 116801, 10.1088/0034-4885/77/11/116801.
94. Wouters, B., Schrama, E.J.O., Improved accuracy of GRACE gravity solutions through empirical orthogonal function filtering of spherical harmonics. Geophys. Res. Lett., 34(23), 2007, L23711, 10.1029/2007GL032098.
95. Yirdaw, S.Z., Snelgrove, K., Agboma, C., GRACE satellite observations of terrestrial moisture changes for drought characterization in the Canadian Prairie. J. Hydrol. 356 (2008), 84–92.
96. Ziehe, A., 2005. Blind Source Separation based on Joint Diagonalization of Matrices with Applications in Biomedical Signal Processing (Ph.D. thesis). Universitat Potsdam. Retrieved from: < http://en.youscribe.com/catalogue/reports-and-theses/knowledge/blind-source-separation-based-on-joint-diagonalization-of-matrices-1424347> (accessed 15.05.15).