(Every day until December 25, I’m posting a science-related image or video and description.)
Day 20In some languages, the word for wind is the same as the word for breath or spirit. “Ruach elohim” means Breath or Spirit of God in Hebrew (one of just a few phrases I remember from college Hebrew class), but the word “ruach” can also refer to the prosaic wind of the world. As a metaphor, it’s a lovely one: though our planet is not living in a strict sense, wind on Earth is the life breath of its atmosphere.
Wind is simply the motion of molecules. A number of factors create and steer wind: a difference in temperature between the planet surface and different layers of air, the rotation of the planet, geographic features like mountains or oceans. The slow change of seasons as Earth orbits the Sun alters the wind patterns, creating large weather features like the monsoon in south Asia and El Niño in the Pacific.
The image above is a still from a computer simulation of Earth’s wind patterns, based on real weather data. Click on the link and see for yourself; the image above is a still, but the simulation shows motion. The colors indicate the different wind speeds; the simulation allows you to pick the altitude where you view the air currents. You can choose the type of world map you want; I picked the Waterman projection for the same reason I like the Dymaxion map, in that it’s a clever way to get around the problems of projecting a sphere onto a flat surface. You can see the shapes of landmasses — islands and continents — and how those affect the wind to varying degrees, depending on how high up you look. (Tip o’ the pendulum to Colin Schultz for sharing this simulation.)
Earth’s winds are different than those on Mars, which lacks oceans, or Saturn, which basically is all ocean (albeit one without a well-defined surface). In all three cases, seasonal variation drives weather changes, and that makes each world’s winds unique. In wind, we see something of the life of a planet. In a world’s breath, we see the dynamic forces that shape it.