Abstract
Morlet wavelets of the meridional component of daily radiosonde wind observations above four West Africa stations were constructed for MayβSeptember seasons, 1950β84, 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 Β© 2003 Royal Meteorological Society