Introduction

In Chad, a country characterized by a dry season and a rainy season, meteorology is crucial for rural populations, who depend on the climate for their agriculture and livestock rearing. Despite the existence of a National Meteorological Agency, the lack of human, technical, and financial resources limits its effectiveness, making forecasts difficult for rural residents. They therefore rely on local beliefs, such as the idea that intense sunshine during the dry season heralds heavy rains. Is this observation based on science, or is it simply a coincidence?

A Hotter Dry Season; A More Extreme Climate?

When the dry season is particularly hot, several natural phenomena are observed: rising temperatures (the sun’s intensity heats the soil, creating arid conditions), high evaporation (bodies of water, such as Lake Chad and rivers, gradually dry out), and intense drought (vegetation suffers, the land cracks, and the dry harmattan winds prevail). These elements seem isolated to the rainy season, but in reality, they influence several meteorological phenomena.

Evaporation and Atmospheric Humidity

Intense sunshine accelerates evaporation, increasing the amount of water vapor in the atmosphere. When the rainy season arrives, this accumulated humidity promotes the formation of dense clouds, leading to more abundant precipitation. This mechanism is based on a fundamental principle of the water cycle: high evaporation leads to more condensation and therefore more rain. Thus, a very hot dry season can, in theory, precede a more intense rainy season.

The Influence of Global Climate Phenomena

Beyond local conditions, global climate cycles such as El Niño and La Niña play a crucial role; El Niño tends to reduce precipitation, exacerbating drought, and La Niña conversely, it favours an increase in precipitation. If a severe drought coincides with a La Niña event, subsequent rains are likely to be more intense. Furthermore, the transition between the dry and rainy seasons is marked by the confrontation between the Dry Harmattan Winds blowing from the Sahara, and the humid monsoon winds, blowing from the Gulf of Guinea. When superheated desert air comes into contact with humid air masses, it creates violent thunderstorms and intense rainfall. Prolonged drought during the dry season can therefore amplify the intensity of future rains.

Conclusion

The adage that a blazing sun during the dry season heralds heavy rains is based on empirical observations confirmed by science. Intense heat increases evaporation and atmospheric contrasts, favouring abundant rainfall. However, meteorology remains influenced by many factors. Strengthening the National Meteorological Agency and making its forecasts accessible to rural populations is crucial. In the meantime, traditional knowledge remains a valuable reference, resonating with modern science.

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