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Annales Geophysicae An interactive open-access journal of the European Geosciences Union
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Volume 20, issue 4
Ann. Geophys., 20, 575–582, 2002
https://doi.org/10.5194/angeo-20-575-2002
© Author(s) 2002. This work is distributed under
the Creative Commons Attribution 3.0 License.
Ann. Geophys., 20, 575–582, 2002
https://doi.org/10.5194/angeo-20-575-2002
© Author(s) 2002. This work is distributed under
the Creative Commons Attribution 3.0 License.

  30 Apr 2002

30 Apr 2002

The relationship between the Sahelian and previous 2nd Guinean rainy seasons: a monsoon regulation by soil wetness?

N. Philippon and B. Fontaine N. Philippon and B. Fontaine
  • Centre de Recherches de Climatologie, UMR 5080 CNRS, Université de Bourgogne, 6 blvd. Gabriel, BP 138, 21000 Dijon, France
  • Correspondence to: N. Philippon
  • (nphilipp@u-bourgogne.fr)

Abstract. The correlation of 0.61 found between observed July–September Sahelian rainfall in year 0 and September–November Guinean rainfall in year - 1, led us to explore the statistical relationships between precipitation, soil moisture and near surface Moist Static Energy (MSE) gradients in West Africa. These analyses were performed over successive 30-year periods and specifically, the most recent period between 1968–1998. It is shown from observations, National Centers for Environmental Predictions and National Center for Atmospheric Research (NCEP/NCAR) reanalyses and from the Global Soil Wetness Project (GSWP) database, that wet Sahelian rainy seasons are preceded by abnormally wet soils over the Sudan-Guinean belt during northern winter. Such moisture anomalies tend to hold during the dry season, then generate increasing MSE gradients just above the continent by March–April. These gradients have been shown to be of prime importance for monsoon dynamics and associated rainfall.

Key words. Hydrology (soil moisture) – Meteorology and atmospheric dynamics (climatology)

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