Particularly in regions, where precipitation is limited to a few months per year only, reliable determination of the onset of the rainy season and the start of the sowing time is of crucial importance to sustainable food production. Especially since the mid-1980s, an increasing delay of onset dates
Long-range prediction of the onset and end of the rainy season in the West African Sahel
β Scribed by J. 'Bayo Omotosho
- Publisher
- John Wiley and Sons
- Year
- 1992
- Tongue
- English
- Weight
- 721 KB
- Volume
- 12
- Category
- Article
- ISSN
- 0899-8418
No coin nor oath required. For personal study only.
β¦ Synopsis
Abstract
Using upperβwind data for three stations across the West African Sahel, simple empirical schemes for predicting the onset and cessation of the rainy season for more than 2 months ahead are presented. Agriculturally reliable rainfall commences about 70 days after the first sudden changes in wind direction from westerly to easterly at the 400 hPa level and above. These sudden changes signal the withdrawal of the subtropical (westerly) jet, thus leading to the establishment of the African easterly jet at the 700 hPa level. Cessation of rainfall occurs about 80 days after the destruction, at the peak of the rainy season, of the midβtropospheric (700β400 hPa) vertical wind shear. A method for estimating the length of the rainy or growing season also is proposed.
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