Waiting for the Monsoon

MALBOROU, NIGER–On a hot afternoon in July, a chanting, dancing, drumming crowd has formed on the main road that crosses the village, half an hour’s drive north of the border with Benin. The villagers have begun the rain dance. They want to bring on the monsoon that drenches the earth every year from June to August; it’s now several weeks late. The millet crop needs 3 months to ripen, and time is running out for planting the seed.

The people who live on the flat, reddish-brown, dusty landscape of southern Niger depend heavily on the West African monsoon: In 2001, 39% of the Nigerian gross domestic product came from agriculture, which employs 90% of the workforce and involves virtually no irrigation. Niger’s neighbors throughout the Sahel, the strip of Africa that stretches across the continent directly south of the Sahara, face similar circumstances. From the 1970s to the 1990s, the Sahel suffered severe drought, leading to some of the worst famines in recent history. Precipitation levels began to rise beginning in the late ’90s, but crops were once more devastated by drought in 2005; 2006 did not begin well.

From Science, August 4, pp 608 –9

Lack of good weather data in Africa means scientists can’t help improve model predictions: the current network of 1152 weather watch stations (not all of which report) is 1/8 the minimum number needed. A European-led consortium of 140 institutions from Europe, America, and Africa has begun a 10-year project to monitor and thoroughly describe the West Africa monsoon: rainfall; cloud structure and water content; amount, movement and characteristics of air-borne particles; distribution of water in river systems; etc.

Africa’s weather is affected by what happens on other continents; in return the Sahara and Sahel regions affect the entire planet. The Sahara supplies much of the world’s aerosols (suspension of fine solid or liquid particles). Sahel weather systems during monsoons affect Atlantic hurricanes (I have no clue how).

Meanwhile current models are all over the place as to what will happen in the future in the Sahel: severe drying, wet conditions, modest drying. Models show varying sensitivity to land or sea temperatures, for example, and with so little data, it’s difficult to fit the models to the data to see which work better.

The rains arrived this year at the end of July; later would have been too late. Hopefully within the decade, it will be possible to know whether this is climate change or seasonal variation.

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