Editorial Type:
Article
Article Type:
Research Article

West African Monsoon Dynamics and Eastern Equatorial Atlantic and Pacific SST Anomalies (1970–88)

Serge Janicot Météo-France, Laboratoire de Météorologie Dynamique du CNRS, Ecole Polytechnique, Palaiseau, France

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Ali Harzallah Laboratoire de Météorologie Dynamique du CNRS, Ecole Normale Supérieure, Paris, France

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Bernard Fontaine CNRS, Centre de Recherches de Climatologie and Laboratoire de Météorologie Dynamique, Dijon, France

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Vincent Moron Centre de Recherches de Climatologie, Université de Bourgogne, Dijon, France

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Print Publication:
01 Aug 1998
DOI:
https://doi.org/10.1175/1520-0442(1998)011<1874:WAMDAE>2.0.CO;2
Page(s):
1874–1882
Restricted access

Abstract

The Laboratoire de Météorologie Dynamique atmospheric GCM is used to investigate relationships between West African monsoon dynamics and SST anomalies in the eastern equatorial Atlantic and Pacific for the period 1970–88. Positive SST anomalies in the eastern equatorial Pacific, mainly associated with a larger east–west divergent circulation over the tropical Atlantic, are found to coincide with negative rainfall anomalies over West Africa. This is the case for the composite ENSO warm episodes of 1972, 1976, 1982, and 1983. By contrast, positive SST anomalies in the eastern equatorial Atlantic are accompanied by a southward shift of the intertropical convergence zone along with negative rainfall anomalies in the Sahel and positive rainfall anomalies in the Guinean region. This was the case in 1987. The ENSO warm event during this year had apparently no significant impact on West African monsoon dynamics. A zonal atmospheric coupling associated with differences of SST anomalies between the eastern equatorial Pacific and the Atlantic is evident in the period 1970–88. Positive (negative) phases of this coupling could enhance the impact of ENSO warm (cold) events on West African monsoon dynamics.

Corresponding author address: Dr. Serge Janicot, Laboratoire de Meteorologie Dynamique, Ecole Polytechique, Route Departementale 36, 91128 Palaiseau CEDEX, France.

Abstract

The Laboratoire de Météorologie Dynamique atmospheric GCM is used to investigate relationships between West African monsoon dynamics and SST anomalies in the eastern equatorial Atlantic and Pacific for the period 1970–88. Positive SST anomalies in the eastern equatorial Pacific, mainly associated with a larger east–west divergent circulation over the tropical Atlantic, are found to coincide with negative rainfall anomalies over West Africa. This is the case for the composite ENSO warm episodes of 1972, 1976, 1982, and 1983. By contrast, positive SST anomalies in the eastern equatorial Atlantic are accompanied by a southward shift of the intertropical convergence zone along with negative rainfall anomalies in the Sahel and positive rainfall anomalies in the Guinean region. This was the case in 1987. The ENSO warm event during this year had apparently no significant impact on West African monsoon dynamics. A zonal atmospheric coupling associated with differences of SST anomalies between the eastern equatorial Pacific and the Atlantic is evident in the period 1970–88. Positive (negative) phases of this coupling could enhance the impact of ENSO warm (cold) events on West African monsoon dynamics.

Corresponding author address: Dr. Serge Janicot, Laboratoire de Meteorologie Dynamique, Ecole Polytechique, Route Departementale 36, 91128 Palaiseau CEDEX, France.

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  • Bottomley, M., C. K. Folland, J. Hsiung, R. E. Newell, and D. E. Parker, 1990: Global Ocean Surface Temperature Atlas ‘GOSTA’. United Kingdom Meteorological Office/Massachusetts Institute of Technology, 20 pp. + 313 plates.

  • Deser, C., and J. M. Wallace, 1990: Large-scale atmospheric circulation features of warm and cold episodes in the tropical Pacific. J. Climate,3, 1254–1281.

  • Dorman, J. L., and P. J. Sellers, 1989: A global climatology of albedo, roughness length and stomatal resistance for atmospheric general circulation models as represented by the simple biosphere model (SIB). J. Appl. Meteor.,28, 833–855.

  • Folland, C. K., T. N. Palmer, and D. E. Parker, 1986: Sahel rainfall and worldwide sea temperature 1901–1985. Nature,320, 602–607.

  • Fontaine, B., and S. Janicot, 1992: Wind field coherence and its variations over West Africa. J. Climate,5, 512–524.

  • ——, and ——, 1996: Near-global SST variability associated with West African rainfall anomaly types. J. Climate,9, 2935–2940.

  • ——, ——, and V. Moron, 1995: Rainfall anomaly patterns and wind field signals over West Africa in August (1958–1989). J. Climate,8, 1503–1510.

  • Fouquart, Y., and B. Bonnel, 1980: Computations of solar heating of the earth’s atmosphere: A new parameterization. Contrib. Atmos. Phys.,53, 35–62.

  • Gates, W. L., 1992: AMIP: The Atmospheric Model Intercomparison Project. Bull. Amer. Meteor. Soc.,73, 1962–1970.

  • Harzallah, A., and R. Sadourny, 1995: Internal versus SST-forced atmospheric variability as simulated by an atmospheric general circulation model. J. Climate,8, 474–495.

  • ——, J. O. Rocha De Aragao, and R. Sadourny, 1996: Interannual rainfall variability in Northern Brazil: Observations and model simulations. Int. J. Climatol.,16, 861–878.

  • Hastenrath, S., 1984: Interannual variability and annual cycle: Mechanisms of circulation and climate in the tropical Atlantic sector. Mon. Wea. Rev.,106, 1280–1287.

  • Houghton, R. W., and Y. M. Tourre, 1992: Characteristics of low-frequency SST fluctuations in the tropical Atlantic. J. Climate,5, 765–771.

  • Janicot, S., 1992: Spatiotemporal variability of West African rainfall. Part II: Associated surface and airmass characteristics. J. Climate,5, 499–511.

  • ——, 1994: The West African monsoons of 1987 and 1988: Pacific or Atlantic signal? Proc. Int. Conf. on Monsoon Variability and Prediction, Trieste, Italy, WMO, 765–772.

  • ——, V. Moron, and B. Fontaine, 1996: Sahel droughts and ENSO dynamics. Geophys. Res. Lett.,23, 515–518.

  • Kidson, J. W., 1975: Tropical eigenvector analysis and the Southern Oscillation. Mon. Wea. Rev.,103, 187–196.

  • Krishnamurti, T. N., 1986: Workbook on numerical weather prediction for the tropics for the training of class I and class II meteorological personnel. WMO Tech. Note No. 669, 355 pp.

  • Lamb, P. J., 1978a: Case studies of tropical Atlantic surface circulation patterns during recent sub-Saharan weather anomalies: 1967 and 1968. Mon. Wea. Rev.,106, 482–491.

  • ——, 1978b: Large-scale tropical surface circulation patterns associated with Subsaharan weather anomalies. Tellus,30, 240–251.

  • Latif, M., and T. P. Barnett, 1995: Interactions of the tropical oceans. J. Climate,8, 952–964.

  • Laval, K., R. Sadourny, and Y. Serafini, 1981: Land surface processes in a simplified GCM. Geophys. Astrophys. Fluid. Dyn.,17, 129–150.

  • Le Treut, H., and Z. X. Li, 1991: Sensitivity of an atmospheric general circulation model to prescribed SST changes: Feedback effects associated with the simulation of cloud optical properties. Climate Dyn.,5, 175–187.

  • Morcrette, J. J., 1990: Radiation and cloud radiative properties in the European Centre for Medium-Range Weather Forecasts forecasting system. J. Geophys. Res.,96, 9121–9132.

  • Moron, V., 1994: Guinean and Saharan rainfall anomaly indices at annual and monthly time scales (1933–1990). Int. J. Climatol.,14, 325–341.

  • ——, S. Bigot, and P. Roucou, 1995: Rainfall variability in subequatorial America and Africa and relationships with the main SST modes (1951–1990). Int. J. Climatol.,15, 1297–1322.

  • Motha, R. P., S. K. Leduc, L. T. Steyaert, C. M. Sakamoto, and N. D. Strommen, 1980: Precipitation patterns in West Africa. Mon. Wea. Rev.,108, 1567–1578.

  • Palmer, T. N., 1986: Influence of the Atlantic, Pacific, and Indian Oceans on Sahel rainfall. Nature,322, 251–253.

  • Pan, Y. H., and A. H. Oort, 1990: Correlation analyses between SST anomalies in the eastern equatorial Pacific and the World Ocean. Climate Dyn.,4, 191–205.

  • Rasmusson, E. M., and T. H. Carpenter, 1982: Variations in tropical SST and surface wind fields associated with the Southern Oscillation. Mon. Wea. Rev.,110, 354–384.

  • Reynolds, R. W., and W. H. Gemmil, 1984: A SST analysis based on in situ and satellite data. Proc. Ninth Annual Climate Diagnostics Workshop, Corvallis, OR, NOAA, 408–416.

  • Rowell, D. P., C. K. Folland, K. Maskell, J. A. Owen, and M. N. Ward, 1992: Modelling the influence of global sea surface temperatures on the variability and predictability of seasonal Sahel rainfall. Geophys. Res. Lett.,19, 905–908.

  • ——, ——, ——, and M. N. Ward, 1995: Variability of summer rainfall over Tropical North Africa (1906–1992): Observations and modelling. Quart. J. Roy. Meteor. Soc.,121, 669–704.

  • Sadourny, R., and K. Laval, 1984: January and July performance of the LMD general circulation model. New Perspectives in Climate Modelling, A. Berger, Ed., Elsevier, 173–198.

  • Semazzi, F. H., V. Metha, and Y. C. Sud, 1988: An investigation of the relationship between Sub-Saharan rainfall and global SSTs. Atmos.–Ocean,26, 118–138.

  • ——, ——, and ——, 1989: Reply to “Comments on an investigation of the relationship between sub-Saharan rainfall and global SSTs.” Atmos.–Ocean,27, 601–605.

  • Servain, J., and J. Merle, 1993: Interannual Climate Variations over the Tropical Atlantic Ocean. Vol. 16, NATO ASI Series, Springer-Verlag, 153–172.

  • ——, J. Picaut, and J. Merle, 1982: Evidence of remote forcing in the equatorial Atlantic Ocean. J. Phys. Oceanogr.,12, 457–463.

  • Ward, M. N., 1992: Provisionally corrected surface wind data, worldwide ocean–atmosphere surface fields, and Sahelian rainfall variability. J. Climate,5, 454–475.

  • Zebiak, S. E., 1993: Air–sea interaction in the equatorial Atlantic region. J. Climate,6, 1567–1586.

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