Windswept_ The Story of Wind and Weather - Marq de Villiers [23]
But it goes beyond this. It is becoming clearer that the sun's activity affects short-term weather patterns and perhaps long-term climate trends. Current thinking is that the solar wind has only a minor long-term effect on climate, although no one really knows, and a great deal of earnest activity is underway to uncover the truth. But with the wind and the weather, the evidence is rather different. As NASA's Dr. James Green puts it, "Changes in the magnetosphere seem to be transmitted to the lower atmosphere, where they may influence the circulation of air masses. If we can discover the physical links between these two regions of our environment that trigger weather and climate changes, we can better predict and prepare for our weather."8
Thus the theater of the air, the stage setting for wind. Wind itself is a product of solar radiation, but it is shaped and affected by planetary rotation, pressure differentials, and by air in all its multiple movements, patterns and paths. And air in turn is affected by ionization, radiation, magnetism, and the cosmic wind. No wonder the ancients found air ineffable and wind mysterious.
CHAPTER THREE
The Search for Understanding
Ivan 's story: All the thunder cells caused by the great furnace of the Saharan summer are tracked by the one-man weather office in Timbuktu and by the slightly more sophisticated operation in Niamey, Niger's capital. Timbuktu's sole meteorologist, Bandiougou Diallo, observes the weather the old-fashioned way—by going onto the roof in a thunderstorm, eyeballing its extent, and hoisting aloft a handheld wind velocity meter. He is there mostly to warn the pilots of Air Mali's venerable Fokker aircraft on their thrice-weekly runs to the city from Bamako, Mali's capital, if it is safe to proceed or more prudent to turn back. But his handwritten notes, forwarded later to his bosses in Bamako, are assembled into broader databanks and used by others to track storm patterns, and thus become part of the global struggle to understand weather systems. Not all the storms he watches cause him or his distant correspondents much concern. Some dissipate locally. Others lose their energy after a day or so. Others persist. A few coalesce into violent weather systems big enough to alert American meteorologists who are monitoring satellite images across the Atlantic.
All thunder cells, though, travel, for that is the nature of the air that has become wind that has transformed itself into a storm.
If you were on the high dunes north of Timbuktu, the wind would have come from the northwest but you could have watched the storm approaching from the east. Saharan storms are easy to see: Sulfurous clouds of yellow sand swirl up into the angry blacks of the clouds. Probably no one was there to see, though. The nomads know better than to be caught on a high dune in a windstorm; they would have taken shelter, such as it was, in the lee of a smaller dune or in a wadi (though mindful of flash floods).
The cell that began at Emi Koussi passed by Timbuktu in the afternoon of August 27. It was one of those whose coherence persisted, and it drifted slowly south of west, passing unrecorded over the ancient capital of the Malian empire, the ruins now known as Koumbi Saleh, and was picked up again by weathermen on the 2Qth, somewhere between the Mauritanian capital, the arid desert town of Nouakchott, and the sprawling and violent slums of Dakar, in Senegal. Airports in both cities kept a wary eye on its passage.
By the end of the day, it had reached the coast. Ahead in its path: the Cape Verde Islands.
This was a complicated place for any weather system to find itself. Behind is the immense furnace of the desert. To the north, aridity. To the south, the sodden hills of Senegal, and beyond them the rain forests beginning at the Gambia River. To the west, the still cold but rapidly warming southbound