MONSOON MYSTERIES IN AMERICA'S SOUTHWEST

摘要

Aplume of moisture vapor flows northeast from Mexico, bearing water from the Gulf of California and the streams and rivers of the Sierra Madre. It collects more water along its route, liberating moisture from swimming pools, sprinklers, and irrigation anals. After a day's march, it stumbles into the 7,000-foot (2,133 meter) Mogollon Rim, the great rock escarpment that separates central Arizona from the high Colorado Plateau. Diverted by air currents, the cloud turns south. As it travels, it grows from cumulus to cumulus congestus, then cumulonim- bus-the towering anvil-head formation that marks a midsummer's skyscape in the desert. Powerful things happen within that mixture of rising air and moisture.