Simulation of West African monsoon using RegCM3 Part II: impacts of deforestation and desertification Article First Online: 12 October 2007 Received: 17 November 2006 Accepted: 29 April 2007 DOI:
Cite this article as: Abiodun, B., Pal, J., Afiesimama, E. et al. Theor Appl Climatol (2008) 93: 245. doi:10.1007/s00704-007-0333-1 Summary
In this study, we investigate the feedback mechanisms between land cover and the monsoon in West African using the International Centre for Theoretical Physics Regional Climate Model (RegCM3). A series of multi-year simulations are performed using reanalysis boundary conditions under three idealised vegetation states (potential, desertified and deforested). The study shows that both desertification and deforestation tend to increase the monsoon flow over the Guinean region, although the mechanisms for change are different in each case. Desertification increases the flow mainly by increasing the meridional temperature gradient. While this reduces rainfall over the desertification region, it increases rainfall to the south. On the other hand, deforestation increases the monsoon flow mainly due to the reduced surface friction experienced by the flow over the Guinean region. This reduces rainfall over the entire West African region.
The study further shows that desertification and deforestation also increase the speed and specific humidity of the mid-tropospheric easterly flow, to the south of the African easterly jet. Consequently, the flow transports more moisture away from the West Africa region at the expense of low-level moisture, resulting in less moisture available for rainfall over the region. Overall, this study suggests that the state of the biosphere in West Africa may play an important role in determining the characteristics of the monsoon and rainfall pattern.
Correspondence: Dr. Babatunde J. Abiodun, Iowa State University, 3134 Agronomy Building, Ames, Iowa, USA
References Afiesimama, EA, Pal, J, Abiodun, BJ, Gutowski, WJ, Adedoyin, A 2006 Simulation of West African Monsoon using the RegCM3. Part I: Model validation and interannual variability Theor Appl Climatol 82 23 38 CrossRef Google Scholar Burke, EJ, Shuttleworth, WJ, Yang, ZL, Mullen, SL, Arain, MA 2000 The impact of parameterization of heteorogenous vegetation on the modelled large-scale circulation in CCM3-BATS Geophys Res 27 397 400 Google Scholar Cadet, DL, Nnoli, NO 1987 Water vapour transport over Africa and the Atlantic ocean during summer 1979 Quart J Roy Meteor Soc 113 581 602 CrossRef Google Scholar Charney, JG 1975 Dynamics of deserts and drought in the Sahel Quart J Roy Meteor Soc 101 193 202 CrossRef Google Scholar Charney, JG, Quirk, WJ, Chow, S-H, Korfield, J 1977 A comparative study of effect albedo change on drought in semi-arid regions J Atmos Sci 34 1366 1385 CrossRef Google Scholar Clark, CB, Xue, Y, Harding, RJ, Valdes, PJ 2001 Modeling the impact of land surface degradation on the climate or tropical north Africa J Climate 14 1809 1822 CrossRef Google Scholar Cook, HK 1999 Generation of the African easterly jet and its role in determining West African precipitation J Climate 12 1165 1184 CrossRef Google Scholar
Dickinson RE, Henderson-Sellers A, Kennedy PJ (1993) Biosphere – atmosphere transfer scheme (BATS) version 1 as coupled to the NCAR Community Climate Model. NCAR Tech. Note NCAR\TN-3871STR, National Center for Atmospheric Research, Boulder, CO, 72 pp
Eltahir, EAB, Gong, CL 1996 Dynamics of wet and dry years in West Africa J Climate 5 1030 1042 CrossRef Google Scholar Folland, CK, Palmer, TN, Parker, DE 1986 Sahel rainfall and worldwide sea temperature, 1901–1985 Nature 320 602 607 CrossRef Google Scholar Fritsch, JM, Chappell, CF 1980 Numerical prediction of convectively driven mesoscale pressure systems. Part 1: Convective parameterisation J Atmos Sci 37 1722 1733 CrossRef Google Scholar Giannini, A, Saravanan, R, Chang, PO 2003 Oceanic forcing of Sahel rainfall on interannual to interdecadal time scales Science 302 1027 1030 CrossRef Google Scholar Grell, GA 1993 Prognostic evaluation of assumptions used by cumulus parameterizations Mon Wea Rev 121 764 787 CrossRef Google Scholar Grist, JP, Nicholson, SE 2001 A study of the dynamic factors influencing the rainfall variability in the West African Sahel J Climate 14 1337 1359 CrossRef Google Scholar Hahmann, AN, Dickinson, R 2001 A fine-mesh approach for general circulation model and its impact on regional climate J Clim 14 1634 1964 CrossRef Google Scholar Holtslag, AAM, De Bruijn, EIF, Pan, H-L 1990 A high resolution air mass transformation model for short-range weather forecasting Mon Wea Rev 118 1561 1575 CrossRef Google Scholar Hulme, M 1992 Rainfall changes in Africa. 1931–1960 to 1961–1990 Int J Climatol 12 685 699 CrossRef Google Scholar Kalnay, E, Kanamitsu, M, Kistler, R, Collins, W, Deaven, D, Gandin, L, Iredell, M, Saha, S, White, G, Woollen, J, Zhu, Y, Chelliah, M, Ebisuzaki, W, Higgins, W, Janowiak, J, Mo, KC, Ropelewski, C, Wang, J, Leetma, A, Reynolds, R, Jenne, R, Joseph, D 1996 The NCEP\NCAR 40-year reanalysis project Bull Amer Meteor Soc 77 437 471 CrossRef Google Scholar
Kiehl JT, Hack JJ, Bonan GB, Boville BA, Breigleb BP, Williamson DL, Rasch PJ (1996) Description of the NCAR community climate Model (CCM3). NCAR Tech. Note, NCAR\TN-420+STR, 152 pp, Natl. Cent. for Atmos. Res; Boulder, Colorado
Lamb, PJ 1978 Large scale tropical Atlantic surface circulations pattern associated with sub-Saharan weather anomalies Tellus 30 240 251 CrossRef Google Scholar
Lamb PJ, Peppler RA (1991) West Africa. In: Glantz M, Kats RW, Nicholson N (eds) Teleconnections Linking Worldwide Climate Anomalies. Cambridge University Press, pp 121–189
Lau, KM, Shen, SSP, Kim, K-M, Wang, H 2006 A multimodel study of the twentieth-century simulations of Sahel drought from the 1970s to 1990s J Geophys Res 111 D07111 CrossRef Google Scholar Maynard, K, Royer, J-F 2004 Sensitivity of a general circulation model to land surface parameters in African tropical deforestation experiments Clim Dynam 22 555 572 Google Scholar Nicholson, SE 1993 An overview of Africa rainfall fluctuation of the last decade J Climate 6 1463 1466 CrossRef Google Scholar Omotosho, J, ‘Bayo, H 1985 The separate contributions of squall lines, thunderstorms and the monsoon to the total rainfall in Nigeria J Climatol 5 543 552 CrossRef Google Scholar Pal, JS, Small, EE, Eltahir, EAB 2000 Simulation of regional-scale water and energy budgets: representation of subgrid cloud and precipitation processes within RegCM J Geophys Res 105 29579 29594 CrossRef Google Scholar
Pal JS, Giorgi F, Bi X, Elguindi N, Solmon F, Gao X, Rauscher SA, Ashfaq M, Francisco R, Bell J, Diffenbaugh N, Karmacharya J, Konaré11 A, Martinez D, da Rocha RP, Sloan LC, Steiner AL, Winter JM, Zakey A (2005) Regional Climate Modeling for the Developing World: The ICTP RegCM3 and RegCNET. In Press BAMS
Peter, M, Tetzlaff, G 1988 The structure of West African squall lines and their environmental moisture budget Meteorol Atmos Phys 39 74 84 CrossRef Google Scholar Reynolds, RW, Rayner, NA, Smith, TM, Stokes, DC, Wang, W 2002 An improved in situ and satellite SST analysis for climate J Climate 15 1609 1625 CrossRef Google Scholar Rowell, DP, Folland, CK, Maskell, K, Ward, MN 1995 Variability of summer rainfall over tropical North Africa (106–92): observation and modeling Quart J Roy Meteor Soc 121 669 704 Google Scholar Taylor, CM, Lambin, EF, Stephenne, N, Harding, RJ, Essery, RLH 2002 The influence of land use change on climate in the Sahel J Climate 15 3615 3629 CrossRef Google Scholar Wang, G, Eltahir, EAB, Foley, JA, Pollard, D, Levis, S 2004 Decadal variability of rainfall in the Sahel: results from the coupled GENESIS-IBIS atmosphere-biosphere model Clim Dynam 22 625 637 Google Scholar Wang, GL, Eltahir, EAB 2000a Role of vegetation dynamics in enhancing the low-frequency variability of the Sahel rainfall Water Resour Res 36 1013 1021 CrossRef Google Scholar Wang, GL, Eltahir, EAB 2000b Ecosystem dynamics and the Sahel drought Geophys Res Lett 27 795 798 CrossRef Google Scholar Webster, PJ, Magaña, VO, Palmer, TN, Shukla, J, Tomas, RA, Yanai, M, Yasunari, T 1998 Monsoons: processes, predictability, and the prospects for prediction J Geophys Res 103 14,451 15,510 CrossRef Google Scholar Xue, Y 1997 Biosphere feedback on regional climate in tropical North Africa Quart J Roy Meteor Soc 123 B 1483 1515 CrossRef Google Scholar Xue, Y, Shukla, J 1993 The influence of land surface properties on Sahel climate. Part I: Desertification J Climate 6 2232 2245 CrossRef Google Scholar Zheng, XY, Eltahir, EAB 1998 The role of vegetation in the dynamics of West African monsoons J Climate 11 2078 2096 Google Scholar