Thank god for air friction. Without it, falling rain would smack into our heads at hundreds of miles per hour. But friction works both ways—falling raindrops also slow down the movement of air molecules in the atmosphere. A new paper in Science calculated that raindrops dissipate as much kinetic energy from the atmosphere as air turbulence. Granted, at 1.8 watts per square meter and 0.75% of the atmosphere’s total kinetic energy, that’s not very much. What’s surprising is that rain drops are pulling more than their weight, as they make up only 0.01% of the atmosphere’s mass.
Researchers calculated the kinetic energy dissipated by a single raindrop and put it together with precipitation rates around the world. Since satellite precipitation data also show the height from which rain started falling, the researchers could plug how far raindrops fell into their energy calculations. It all adds up across the whole globe: the researchers estimate the total rate of energy dissipation from rainfall to be 1015 Watts. That’s a lot of energy, but still unlikely to affect major weather phenomena like hurricanes or tornados.
[via Nature News]
Image via Shutterstock
The 2000s, the “aughts”—whatever you want to call the first decade of the 21st century, you can also call it the warmest 10 years on record. The National Oceanic and Atmospheric Administration just released its annual “State of the Climate” report, and after sampling 37 climate indicators including the biggies like sea surface temperature, glacier cover, and sea level, they came to that conclusion.
The NOAA report—published in the Bulletin of the American Meteorological Society—is different from other climate publications, because it’s based on observed data, not computer models, making it the “climate system’s annual scorecard,” the authors wrote… “It’s telling us what’s going on in the real world, rather than the imaginary world,” said Kevin Trenberth, a senior scientist at the Boulder, Colorado-based National Center for Atmospheric Research [National Geographic].
While one climate group trumpets its mountain of climate data, the scientists at the University of East Anglia are just climbing out from the scandal that broke out over theirs. This month another investigation cleared the Climate Research Unit of scientific misconduct or dishonesty, without condoning the emails’ tone or the unit’s handling of the controversy.