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Rainy Season Onset Date

Onset of the West African Monsoon

Determining the start of the rainy season.

An important aspect of African meteorology is when the rainy season begins (known as the 'rainy season onset date').  Historical observations are used to define the typical rainy season onset for different regions ('climatology').  Current observations are then compared with the climatology in order to determine whether the rains are early or late for a particular season.

The data set used here is the daily Climate Prediction Centre Famine Early Warning System Rainfall Estimates ( FEWS-NET CPC-FEWS RFE).  This data set was selected because it has been generated from both a combination of satellite and ground-based observations. Data sets that include satellite data over Africa are useful as ground-based observations data are very sparse in this region, and using these observations alone can result in a data set with very large errors.

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