Early detection of the start of the wet season in semiarid tropical climates of western Africa

An earlier paper (Jolliffe IT, Sarria‐Dodd DE. 1994. International Journal of Climatology 14: 71–76) investigated the problem of deciding when the wet season has started in tropical and sub‐tropical climates. In particular, methodology based on linear discriminant analysis was developed for using data from the current season to make the decision, rather than relying only on information from previous seasons. It was shown, for three stations in eastern Africa, that the methodology was potentially valuable. The present study is much larger, using data from 24 stations, covering a range of annual rainfall totals, in western Africa. It is confirmed that linear discriminant analysis can indeed be useful in detecting when the wet season has started, and hence in deciding when to plant crops. As well as being a larger analysis than that reported previously, the present study also extends the previous work by investigating an alternative definition of the start of the wet season and by including ‘date’ as a potential explanatory variable. Copyright © 2001 Royal Meteorological Society