Relationships between rainfall and West African wave disturbances in station observations

Authors

  • El Houssein Taleb,

    1. Department of Geography, Vrije Universiteit Brussel, Pleinlaan 2, 1050 Brussels, Belgium
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  • Leonard M. Druyan

    Corresponding author
    1. Center for Climate Systems Research, Earth Institute at Columbia University and the NASA/Goddard Institute for Space Studies, 2880 Broadway, New York, NY 10025, USA
    • Center for Climate Systems Research, Earth Institute at Columbia University and the NASA/Goddard Institute for Space Studies, 2880 Broadway, New York, NY 10025, USA
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Abstract

Morlet wavelets of the meridional component of daily radiosonde wind observations above four West Africa stations were constructed for May–September seasons, 1950–84, at three vertical levels. The passage of African wave disturbances (AWDs) at each station was detected as statistically significant wavelet amplitudes within two spectral bands. The detected AWD activity, or lack of it, was compared with the precipitation record at each station. Results demonstrate that AWDs account for only a proportion of the seasonal rainfall, implying that other precipitation triggers are also important. In addition, the analysis finds that many AWD traversals fail to initiate heavy rainfall at the selected stations. At Niamey, the average precipitation amount per wave had a positive trend between 1953 and 1978. With few exceptions, seasonal precipitation totals were not correlated with the number of days on which AWDs were detected. Although the seasonal average precipitation amount per AWD day exhibited a positive trend at Niamey between 1953 and 1978, there was no corresponding interannual trend in total seasonal precipitation. Copyright © 2003 Royal Meteorological Society

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