Rainfall saps so much energy from the sky that it may slow down atmospheric circulation if Earth’s climate continues to warm. That's the conclusion of a new study, in which researchers have for the first time estimated the average amount of energy robbed from the atmosphere by friction in the airflow around falling raindrops (artist’s concept shown). The data indicate that, between 30°N and 30°S—a broad swath around Earth’s equator that stretches approximately from New Orleans, Louisiana, to southernmost Brazil—the energy drained from the air by all raindrops from ground level up totals about 1.8 watts per square meter, about half the energy emitted by a night-light. Because climate models suggest that global average precipitation will increase between 1% and 2% for each 1°C rise in average temperature, the extra energy drained from the atmosphere by raindrop-induced friction will likely result in less energy available to drive winds, weather systems, and other atmospheric motions, researchers report online today in Science.
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