Land surface processes and Sahel climate

Reviews of Geophysics

Volumn 38, Issue 1, 2000, Pages 117-139

  Nicholson, Sharon ^a  

^a FLORIDA STATE UNIVERSITY   (United States)

Author keywords

[No Author keywords available]

Indexed keywords

ATMOSPHERE-BIOSPHERE INTERACTION; LAND SURFACE; PRECIPITATION (CLIMATOLOGY); RAINFALL;

AFRICA; SAHEL;

EID: 84940613269     PISSN: 87551209     EISSN: None     Source Type: Journal    
DOI: 10.1029/1999RG900014     Document Type: Review

References (137)

1. Ahlcrona, E., The Impact of Climate and Man of Land Transformation in Central Sudan, Lund Univ. Press, Lund, Sweden, 1988.
2. Akhtar-Schuster, M., Degradationsprozesse und Desertifikation im semiariden randtropischen Gebiet der Butana/Rep. Sudan, Goettinger Beitr. Land Forstwirstsch. Tropen Subtropen, 105, 1995.
3. Andreae, M. O., Climatic effects of changing atmospheric aerosols levels, in World Survey of Climatology, vol. 16, Future Climates of the World, edited by A. Henderson-Sellers, pp. 341-392, Elsevier, New York, 1995.
4. Andreae, M. O., Raising dust in the greenhouse, Nature, 380, 389-390, 1996.
5. Barnston, A. G., and P. T. Schickedanz, The effect of irrigation on warm season precipitation in the southern Great Plains, J. Clim. Appl. Meteorol., 23, 865-888, 1984.
6. ben Mohamed, A., and J. P.-Frangi, Humidity and turbidity parameters in Sahel: A case study for Niamey (Niger), J. Clim. Appl. Meteorol., 22, 1820-1823, 1983.
7. ben Mohamed, A., and J. P.-Frangi, Results from ground-based monitoring of spectral aerosol optical thickness and horizontal extinction: Some characteristics of dusty Sahelian atmospheres, J. Clim. Appl. Meteorol., 25, 1807-1815, 1986.
8. ben Mohamed, A., J. P. Frangi, J. Fontan, and A. Druilhet, Spatial and temporal variations of atmospheric turbidity and related parameters in Niger, J. Appl. Meteorol., 31, 1286-1294, 1992.
9. Bergametti, G., L. Gomes, G. Coude-Gaussen, P. Rognon, and M.-N. Le Coustumer, African dust observed over Canary Islands: Source-regions identification and transport pattern for some summer situations, J. Geophys. Res., 94, 14,855-14,864, 1989.
10. Blyth, E. M., Representing heterogeneity at the southern super site with average surface parameters, J. Hydrol. Amsterdam, 188-189, 869-877, 1997.
11. Blyth, E. M., A. J. Dolman, and N. Wood, Effective resistance to sensible- and latent-heat flux in heterogeneous terrain, Q. J. R. Meteorol. Soc., 119, 423-442, 1993.
12. Bounoua, L., and T. N. Krishnamurti, Influence of soil moisture on Sahelian climate prediction, I, Meteorol. Atmos. Phys., 52, 183-203, 1993a.
13. Bounoua, L., and T. N. Krishnamurti, Influence of soil moisture on Sahelian climate prediction, II, Meteorol. Atmos. Phys., 52, 205-224, 1993b.
14. Braud, I., P. Bessemoulin, B. Monteny, M. Sicot., J. P. Vandervaere, and M. Vauclin, Unidimensional modelling of a fallow savannah during the HAPEX-Sahel experiment using the SiSPAT model, J. Hydrol. Amsterdam, 188-189, 912-945, 1997.
15. Bromley, M. J., P. Lewis, M. Sutherland, J. P. Muller, Estimating land surface albedo in the HAPEX-Sahel southern super-site: Inversion of two BRDF models against multiple ASAS images, J. Hydrol. Amsterdam, 188-189, 139-154, 1997.
16. Brubaker, K. L., and D. Entekhabi, Nonlinear dynamics of water and energy balance in land-atmosphere interaction, Tech. Rep. 341, Ralph M. Parsons Lab., Mass. Inst. of Technol., Cambridge, 1994.
17. Brubaker, K. L., and D. Entekhabi, Asymmetric recovery from wet versus dry soil moisture anomalies, J. Clim. Appl. Meteorol., 35, 94-109, 1996.
18. Brubaker, K. L., D. Entekhabi, and P. S. Eagleson, Estimation of continental precipitation recycling, J. Clim., 6, 1077-1089, 1993.
19. Bryson, R. A., Drought in Sahelia: Who or what is to blame?, Ecologist, 3, 366-371, 1974.
20. Carlson, T. N., and S. G. Benjamin, Radiative heating rates for Saharan dust, J. Atmos. Sci., 37, 193-213, 1980.
21. Cerf, A., Atmospheric turbidity over West Africa, Contrib. Atmos. Phys., 53, 414-428, 1980.
22. Chang, C.-B., Impact of desert environment on the genesis of African wave disturbances, J. Atmos. Sci., 50, 2137-2145, 1993.
23. Charney, J. G., The dynamics of deserts and droughts, Q. J. R. Meteorol. Soc., 101, 193-202, 1975.
24. Clark, C. A., and R. W. Arritt, Numerical simulations of the effect of soil moisture and vegetation cover on the development of deep convection, J. Appl. Meteorol., 34, 2029-2045, 1995.
25. Claussen, M., Modeling bio-geophysical feedback in the Sahel, Rep. 163, Max-Planck-Inst. für Meteorol., Hamburg, Germany, 1995.
26. Cook, K. H., Mechanisms by which surface drying perturbs tropical precipitation fields, J. Clim., 7, 400-413, 1994.
27. Cook, K. H., Large-scale atmospheric dynamics and Sahelian precipitation, J. Clim., 10, 1137-1152, 1997.
28. Cook, K. H., and A. Ganadeskian, Effects of saturated and dry land surfaces on tropical circulation and precipitation in a general circulation model, J. Clim., 4, 873-889, 1991.
29. d'Almeida, G. A., A model for Saharan dust transport, J. Clim. Appl. Meteorol., 25, 903-916, 1986.
30. d'Almeida, G. A., On the variability of desert aerosol radiative characteristics, J. Geophys. Res., 92, 3017-3026, 1987.
31. de Groen, M. M., and H. H. G. Savenije, Do land use induced changes of evaporation affect rainfall in Southeastern Africa?, Phys. Chem. Earth, 20, 515-519, 1995.
32. Delworth, T., and S. Manabe, Climate variability and land-surface processes, Adv. Water Resour., 16, 3-20, 1993.
33. Desconnets, J. C., J. D. Taupin, T. Lebel, and C. Leduc, Hydrology of the HAPEX-Sahel central super-site: Surface water drainage and aquifer recharge through the pool systems, J. Hydrol. Amsterdam, 188-189, 155-178, 1997.
34. Dirmeyer, P. A., and J. Shukla, The effect on regional and global climate of expansion of the world's deserts, Q. J. R. Meteorol. Soc., 122, 451-482, 1996.
35. Dolman, A. J., and E. M. Blyth, Patch scale aggregation of heterogeneous land surface cover for mesoscale meteorological models, J. Hydrol. Amsterdam, 190, 252-268, 1997.
36. Dolman, A. J., et al., The role of the land surface in Sahelian climate: HAPEX-Sahel results and future research needs, J. Hydrol. Amsterdam, 188-189, 1067-1079, 1997a.
37. Dolman, A. J., A. D. Culf, and P. Bessemoulin, Observations of boundary layer development during the HAPEX-Sahel intensive observation period, J. Hydrol. Amsterdam, 188-189, 998-1016, 1997b.
38. Druilhet, A., and P. Durand, Etude de la couche limite convective sahélienne en présence de brumes sèches (Expérience ECLATS), Boundary Layer Meteorol., 28, 51-77, 1984.
39. Druyan, L. M., and T. M. Hall, The sensitivity of African wave disturbances to remote forcing, J. Appl. Meteorol., 35, 1100-1110, 1996.
40. Duce, R., Sources, distributions, and fluxes of mineral aerosols and their relationship to climate, in Dahlem Workshop on Aerosol Forcing of Climate, edited by R. J. Charlson and J. Heintzenberg, pp. 43-72, Berlin, 1995.
41. Duvel, J. P., Convection over tropical Africa and the Atlantic Ocean during northern summer, part II, Modulation by easterly waves, Mon. Weather Rev., 118, 1855-1868, 1990.
42. Eltahir, E. A. B., and C. Gong, Dynamics of wet and dry years in West Africa, J. Clim., 9, 1030-1042, 1996.
43. Entekhabi, D., Recent advances in land-atmosphere interaction research, U.S. Natl. Rep. Int. Union Geod. Geophys. 1991-1994, Rev. Geophys., 995-1003, 1995.
44. Entekhabi, D., and I. Rodriguez-Iturbe, An analytic framework for the characterization of the space-time variability of soil moisture, Adv. Water Resour., 17, 35-45, 1994.
45. Entekhabi, D., I. Rodriguez-Iturbe, and R. L. Bras, Variability in large-scale water balance with a land surface-atmosphere interaction, J. Clim., 5, 798-813, 1992.
46. Faizoun, C. A., A. Podaire, and G. Dedieu, Monitoring of Sahelian aerosol and atmospheric water vapor content characteristics from Sun photometer measurements, J. Clim. Appl. Meteorol., 33, 1291-1303, 1994.
47. Fennessy, M. J., and J. Shukla, Impact of initial soil wetness of seasonal atmospheric prediction, COLA Tech. Rep., 34, Cent, for Ocean-Land-Atmos, Studies, Calverton, Md., 1996.
48. Folland, C. K., D. E. Parker, M. N. Ward, and A. W. Colman, Prediction of seasonal rainfall in the Sahel region of Africa using empirical and dynamical methods, J. Forecasting, 10, 2-56, 1991.
49. Fouquart, Y., B. Bonnell, G. Brogniez, J. C. Buriez, L. Smith, J. J. Morcrette, and A. Cerf, Observations of Saharan aerosols: Results of ECLATS field experiment, II, Broadband radiative characteristics of the aerosols and vertical radiative flux divergence, J. Clim. Appl. Meteorol., 26, 38-52, 1987a.
50. Fouquart, Y., B. Bonnell, M. Chaoui Roquai, and R. Santer, Observations of Saharan aerosols: Results of ECLATS field experiment, I, Optical thicknesses and aerosol size distributions, J. Clim. Appl. Meteorol., 26, 28-37, 1987b.
51. Gash, J. H. C., et al., The variability of evaporation during the HAPEX-Sahel intensive observation period, J. Hydrol. Amsterdam, 188-189, 385-399, 1997.
52. Goldenberg, S. B., and L. J. Shapiro, Physical mechanisms for the association of El Nino and West African rainfall with Atlantic major hurricane activity, J. Clim., 9, 1169-1187, 1996.
53. Gong, C., and E. Eltahir, Sources of moisture for rainfall in West Africa, Water Resour. Res., 32, 3115-3121, 1996.
54. Goutourbe, J. P., et al., A large-scale observational study of land-atmosphere interaction in the semi-arid tropics, Ann. Geophys., 12, 53-64, 1994.
55. Goutourbe, J. P., J. Noilhan, P. Lacarrere, and I. Braud, Modelling of the atmospheric column over the Central sites during HAPEX-Sahel, J. Hydrol. Amsterdam, 188-189, 1017-1039, 1997.
56. Graetz, R. D., Desertification: A Tale of Two Feedbacks, in Ecosystem Experiments, edited by H. A. Mooney et al., pp. 59-87, John Wiley, New York, 1991.
57. Guedalia, D., C. Estournel, and R. Vehil, Effects of Sahel dust layers upon nocturnal cooling of the atmosphere (ECLATS Experiment), J. Clim. Appl. Meteorol., 23, 644-650, 1984.
58. Hare, F. K., Climate and Desertification: A revised analysis, World Meteorol. Org., Geneva, Switzerland, 1983.
59. Hellden, U., Drought impact monitoring: A remote sensing study of desertification in Kordofan, Sudan, Rep., 61, Lunds Univ. Naturgeogra. Inst., 1984.
60. Hellden, U., Desertification: Time for an assessment?, Ambio, 20, 372-383, 1991.
61. Holben, B. N., T. F. Eck, and R. S. Fraser, Temporal and spatial variability of aerosol optical depth in the Sahel region in relationship to vegetation remote sensing, Int. J. Remote Sens., 12, 1147-1164, 1991.
62. Husar, R. B., J. M. Prospero, and L. L. Stower, Characterization of tropospheric aerosols over the oceans with the NOAA advanced very high resolution radiometer optical thickness operational product, J. Geophys. Res., 102, 16,889-16,909, 1997.
63. Jacobs, C. M. J., and H. A. R. de Bruin, The sensitivity of regional transpiration to land-surface characteristics: Significance of a feedback, J. Clim., 5, 682-698, 1992.
64. Kabat, P., A. J. Dolman, and J. A. Elbers, Evaporation, sensible heat and surface conductance of fallow savanna and patterned woodland in the Sahel, J. Hvdrol. Amsterdam, 188-189, 494-515, 1997.
65. Karyampudi, V. M., and T. N. Carlson, Analysis and numerical simulations of the Saharan air layer and its effects on easterly wave disturbances, J. Atmos. Sci., 45, 3102-3136, 1988.
66. Koster, R. D., and M. J. Suarez, The influence of land surface moisture retention on precipitation statistics, J. Clim., 9, 2551-2567, 1996.
67. Lamb, P. J., West African water vapor variations between recent contrasting sub-Saharan rainy seasons, Tellus, 35, 198-212, 1983.
68. Lamb, P. J., M. A. Bell, and J. D. Finch, Variability of Sahelian disturbance lines and rainfall during 1951-1987, in Water Resources Variability in Africa During the XXth Century, edited by E. Servat et al., pp. 19-26, Int. Assoc. of Hydrol. Sci., Gentbrugge, Belgium, 1998.
69. Lare, A. R., and S. E. Nicholson, Contrasting conditions of surface water balance in wet years and dry years as a possible land surface-atmosphere feedback mechanism in the West African Sahel, J. Clim., 7, 653-668, 1994.
70. Le Barbé, L., and T. Lebel, Rainfall climatology of the HAPEX-Sahel region during the years 1950-1990, J. Hydrol. Amsterdam, 188-189, 43-73, 1997.
71. Lebel, T., L. Le Barbé, and N. D'Amato, Rainfall monitoring during HAPEX-Sahel, I, General rainfall conditions and climatology, J. Hydrol. Amsterdam, 188-189, 74-96, 1997.
72. Leduc, C., J. Bromley, and P. Schroeter, Water table fluctuation and recharge in semi-arid climate: Some results of the HAPEX-Sahel hydrodynamic survey (Niger), J. Hydrol. Amsterdam, 188-189, 123-138, 1997.
73. Li, X., H. Maring, D. Savoie, K. Voss, and J. J. Prospero, Dominance of mineral dust in aerosol light scattering in the North Atlantic trade winds, Nature, 380, 416-419, 1996.
74. Lofgren, B. M., Sensitivity of land-ocean circulations, precipitation, and soil moisture to perturbed land surface albedo, J. Clim., 8, 2521-2542, 1995a.
75. Lofgren, B. M., Surface albedo-climate feedback simulated using two-way coupling, J. Clim., 8, 2543-2562, 1995b.
76. Mainguet, M., Desertification, Natural Background and Human Mismanagement, Springer-Verlag, New York, 1991.
77. Marengo, J. A., S. E. Nicholson, A. R. Lare, B. A. Monteny, and S. Galle, Application of evapoclimatonomy to monthly surface water balance calculations at the HAPEX-Sahel supersites, J. Appl. Meteorol., 35, 562-573, 1996.
78. Miller, R. L., and R. Lindzen, Organization of rainfall by an unstable jet with an application to African waves, J. Atmos. Sci., 49, 1523-1540, 1992.
79. Mozer, J. B., and J. A. Zehnder, Lee vorticity production by large-scale tropical mountain ranges, II, A mechanism for the production of African waves, J. Atmos. Sci., 53, 539-549, 1996.
80. Nicholson, S. E., African drought: An example of the influence of land-surface properties on climate?, in Proceedings of the ISLSCP Conference, Eur. Space Agency Spec. Publ., ESA SP-248, 405-410, 1986.
81. Nicholson, S. E., Land surface-atmosphere interaction: Physical processes and surface changes and their impact, Prog. Phys. Geogr., 12, 36-65, 1988.
82. Nicholson, S. E., African Drought: Characteristics, Causal Theories and Global Teleconnections, in Understanding Climate Change, Geophys. Monogr. Ser., vol. 52, edited by A. Berger, R. E. Dickinson, and J. W. Kidson, pp. 79-100, AGU, Washington, D. C., 1989.
83. Nicholson, S. E., The need for a reappraisal of the question of large-scale desertification: Some arguments based on consideration of rainfall fluctuations, in Report of the SAREC-Lund International Meeting on Desertification, Univ. of Lund, Lund, Sweden, 1990.
84. Nicholson, S. E., An overview of African rainfall fluctuations of the last decade, J. Clim., 6, 1463-1466, 1993.
85. Nicholson, S. E., Desertification, in Encyclopedia of Climate and Weather, edited by S. H. Schneider, pp. 239-242, Oxford Univ. Press, New York, 1994.
86. Nicholson, S. E., Variability of African rainfall on interannual and decadal time scales in Natural Climate Variability on Decade-to-Century Time Scales, edited by Climate Research Committee, pp. 32-43, Nat. Academy Press, Washington, D. C., 1995.
87. Nicholson, S. E., J. Y. Kim, and J. Hoopingarner, Atlas of African rainfall and its interannual variability, Fla. State Univ., Tallahassee, 1988.
88. Nicholson, S. E., M. B. Ba, and J. Y. Kim, Rainfall in the Sahel during 1994, J. Clim., 9, 1673-1676, 1996.
89. Nicholson, S. E., C. J. Tucker, and M. B. Ba, Desertification, drought and surface vegetation: An example from the West African Sahel, Bull. Am. Meteorol. Soc., 79, 815-829, 1998.
90. Noilhan, J., P. Lacarrère, A. J. Dolman and E. M. Blyth, Defining area-average parameters in meteorological models for landsurfaces with mesoscale heterogeneity, J. Hydrol. Amsterdam, 190, 302-316, 1997.
91. N'Tchayi Mbourou, G. M., J. Bertrand, M. Legrand and J. Baudet, Temporal and spatial variations of the atmospheric dust loading throughout West Africa over the last thirty years, Ann. Geophys., 12, 265-273, 1994.
92. N'Tchayi Mbourou, G. M., J. Bertrand, and S. E. Nicholson, The diurnal and seasonal cycles of wind-borne dust over Africa north of the equator, J. Appl. Meteorol., 36, 868-882, 1997.
93. Olsson, L., An Integrated Study of Desertification: Applications of Remote Sensing, GIS and Spatial Models in Semi-Arid Sudan, Univ. of Lund, Lund, Sweden, 1985.
94. Oluwafemi, C. O., Preliminary solar spectro-photometric measurements of aerosol optical density at Lagos, Nigeria, Atmos. Environ., 13, 1611-1615, 1979.
95. Otterman, J., Baring high-albedo soils by overgrazing: A hypothesized desertification mechanism, Science, 186, 531-533, 1974.
96. Peugeot, C., M. Esteves, S. Galle, J. L. Rajot, and J. P. Vandervaere, Runoff generation processes: Results and analysis of field data collected at the east central super of the HAPEX-Sahel experiment, J. Hydrol. Amsterdam, 188-189, 179-202, 1997.
97. Pinker, R. T., G. Idemudia, and T. O. Aro, Characteristic aerosol optical depths during the Harmattan season in sub-Saharan Africa, Geophys. Res. Lett., 21, 685-688, 1994.
98. Prentice, I. C., et al., A global biome model based on plant physiology and dominance, soil properties and climate, J. Biogeogr., 19, 117-134, 1992.
99. Prince, S. D., E. Brown de Colstoun, and L. L. Kravitz, Evidence from rain-use efficiencies does not indicate extensive Sahelian desertification, Global Change Biol., 4, 359-374, 1998.
100. Prospero, J. M., Saharan dust transport over the North Atlantic Ocean and Mediterranean, in The Impact of African Dust Across the Mediterranean, Kluwer, 133-151, 1996.
101. Prospero, J. M., The atmospheric transport of particles to the ocean, in Particle Flux in the Ocean, Scope Rep., vol. 57, edited by V. Ittekkot, et al., pp. 19-52, John Wiley, New York, 1997.
102. Prospero, J. M., and R. T. Nees, Impact of the North African drought and el Nino on mineral dust in the Barbados trade winds, Nature, 320, 735-738, 1986.
103. Prospero, J. M., D. L. Savoie, R. Arimoto, and F. Huang, Long-term trends in African mineral dust concentrations over the western North Atlantic: Relationship to North African rainfall, Eos Trans. AGU, 74(43), 146, 1993.
104. Puigdefabregas, J., Desertification: Stress beyond resilience, exploring a unifying process structure, Ambio, 24, 311-313, 1995.
105. Rodriguez-Iturbe, I., D. Entekhabi, and R. L. Bras, Nonlinear dynamics of soil moisture at climate scales, 1., Stochastic analysis, Water Resour. Res., 27, 1899-1906, 1991.
106. Rowell, D. P., and C. Blondin, The influence of soil wetness distribution on short-range rainfall forecasting in the West African Sahel, Q. J. R. Meteorol. Soc., 116, 1471-1485, 1990.
107. Rowell, D., and J. Milford, On the generation of African squall lines, J. Clim., 6, 1181-1193, 1993.
108. Rowell, D. P., C. K. Folland, K. Maskell, and M. N. Ward, Variability of summer rainfall over tropical North Africa (1906-1992): Observations and modelling, Q. J. R. Meteorol. Soc., 121, 669-704, 1995.
109. Savenije, H. H. G., New definitions for moisture recycling and the relationship with land-use changes in the Sahel, J. Hydrol. Amsterdam, 167, 57-78, 1995.
110. Schlesinger, W. H., J. F. Reynolds, G. L. Cunningham, L. F. Huenneke, W. M. Jerrell, R. A. Virginia, and W. G. Whitford, Biological feedbacks in global desertification, Science, 247, 1043-1048, 1990.
111. Scott, R., R. Koster, D. Entekhabi, and M. Suarez, Effect of a canopy interception reservoir on hydrological persistence in a general circulation model, J. Clim., 8, 1917-1922, 1995.
112. Scott, R., D. Entekhabi, R. Koster, and M. Suarez, Timescales of land surface evapotranspiration response, J. Clim., 10, 559-566, 1997.
113. Semazzi, F. H. M., and L. Sun, On the modulation of the Sahelian summer rainfall by bottom topography, paper presented at the Sixth Symposium on Global Change Studies, Am. Meteorol. Soc., Dallas, Tex., 1995.
114. Shukla, J., Dynamical predictability of monthly means, J. Atmos. Sci., 38, 2547-2572, 1981.
115. Sud, Y. C., and A. Molod, A GCM simulation study of the influence of Saharan evapotranspiration and surface-albedo anomalies on July circulation and rainfall, Mon. Weather Rev., 116, 2388-2400, 1988.
116. Sud, Y. C., W. C. Chao, and G. K. Walker, Dependence of rainfall on vegetation: Theoretical considerations, simulation experiments, observations, and inferences from simulated atmospheric soundings, J. Arid Environ., 25, 5-18, 1993.
117. Sud, Y. C., K. M. Lau, G. K. Walker, and J.-H. Kim, Understanding biosphere-precipitation relationships: Theory, model simulations, and logical inferences, Mausam, 1995.
118. Taylor, C. M., and T. Lebel, Observational evidence of persistent convective scale rainfall patterns, Mon. Weather Rev., 126, 1597-1607, 1998.
119. Taylor, C. M., R. J. Harding, A. J. Thorpe, and P. Bessemoulin, A mesoscale simulation of land surface heterogeneity from HAPEX-Sahel, J. Hydrol. Amsterdam, 188-189, 1040-1066, 1997.
120. Tegen, I., and I. Fung, Modeling of mineral dust in the atmosphere: Sources, transport, and optical thickness, J. Geophys. Res., 99, 22,897-22,914, 1994.
121. Tegen, I., and I. Fung, Contribution to the atmospheric mineral aerosol load from land surface modification, J. Geophys. Res., 100, 18,707-18,726, 1995.
122. Tegen, I., A. A. Lacis, and I. Fung, The influence of mineral aerosols from disturbed soils on the global radiation budget, Nature, 380, 419-422, 1996.
123. Thierry, J. H., J.-M. d'Herbes, and C. Valentin, A model simulating the genesis of banded vegetation patterns in Niger, J. Ecol., 83, 497-507, 1995.
124. Thomas, D. S. G., and N. J. Middleton, Desertification: Exploding the Myth, John Wiley, New York, 1994.
125. Thorncroft, C. D., and B. J. Hoskins, An idealized study of African easterly waves, I, A linear view, Q. J. R. Meteorol. Soc., 120, 953-982, 1994a.
126. Thorncroft, C. D., and B. J. Hoskins, An idealized study of African easterly waves, II, A nonlinear view, Q. J. R. Meteorol. Soc., 120, 983-1015, 1994b.
127. Tucker, C. J., and S. E. Nicholson, Variations in the size of the Sahara, 1980 to 1997, Ambio, 28, 587-591, 1999.
128. Tucker, C. J., H. E. Dregne, and W. W. Newcomb, Expansion and contraction of the Sahara desert from 1980 to 1990, Science, 253, 299-301, 1991.
129. United Nations, Desertification, edited by M. K. Biswas and A. K. Biswas, Pergamon, Tarrytown, N. Y., 1980.
130. Wai, M. M.-K., E. A. Smith, P. Bessemoulin, A. D. Culf, A. J. Dolman, and T. Lebel, Variability in boundary layer structure during HAPEX-Sahel wet-dry season transition, J. Hydrol. Amsterdam, 188-189, 965-997, 1997.
131. Ward, N. M., Provisionally corrected surface wind data, worldwide ocean-atmosphere surface fields, and Sahelian rainfall variability, J. Clim., 5, 454-475, 1992.
132. Ward, N. M., Diagnosis and short-lead time prediction of summer rainfall in tropical North Africa at interannual and multidecadal timescales, J. Clim., 11, 3167-3191, 1998.
133. Warren, A., Desertification, in The Physical Geography of Africa, edited by W. M. Adams, A. S. Goudie, and A. R. Orme, pp. 342-355, Oxford Univ. Press, New York, 1996.
134. Xue, Y., Biosphere feedback on regional climate in tropical north Africa, Q. J. R. Meteorol. Soc., 123, 1483-1515, 1997.
135. Xue, Y., and J. Shukla, The influence of land surface properties on Sahel climate, I, Desertification, J. Clim., 6, 2232-2345, 1993.
136. Xue, Y., and J. Shukla, The influence of land surface properties on Sahel climate, II, Afforestation, J. Clim., 9, 3260-3275, 1996.
137. Xue, Y., K.-N. Liou, and A. Kasahara, Investigation of biogeophysical feedback over the African continent using a 2-D model, J. Clim., 3, 337-352, 1990.