Wind
Here I am sitting at my desk. I’m meant to be doing some work but it’s really windy outside and I find myself just sitting and listening to the wind...
So let’s talk wind. What is it? In a nutshell, it’s moving air.
When air is warmed it expands and becomes less dense, and so rises, and cool air comes in to take its place. This movement creates different pressures in the atmosphere which creates the winds around the globe.
Wind is caused by air flowing from high pressure to low pressure. The closer the high and low pressure areas are together, the stronger the pressure gradient, and the stronger the winds. However, because the Earth is rotating the air does not flow directly from high to low pressure. Rather, it gets deflected to the right in the Northern Hemisphere and to the left in the Southern Hemisphere, so that the wind flows mostly around the high and low pressure areas. (This deflection is due to the Coriolis effect - which, whilst being a real thing, does NOT cause water to drain out of your toilet/sink in a particular direction. I’ve written a post on that previously. I’ll repost it tomorrow.)
The prevailing wind is a type of wind that usually blows in a region. There are a series of bands around the globe that have steadily blowing prevailing winds near the surface. Different prevailing winds have different names - polar easterlies, westerlies, and tradewinds (which are essentially equatorial easterlies). Easterly winds blow from east to west, whilst westerly winds blow from west to east.
Winds are also named according to how fast they are moving. This method is referred to as the Beaufort Scale. The scale ranges from 0 (calm air, < 1 km/h) to 12 (hurricane force, > 117 km/h). In between these two we have light air, light breeze, gentle breeze, moderate breeze, fresh breeze, strong breeze, near gale, gale, strong gale, storm, and violent storm.
Near the surface of the Earth, friction with the ground slows the wind down. During the day, when convective mixing is stirring up the lower atmosphere, this effect is minimised. At night when convective mixing has stopped, the surface wind can slow considerably, or even completely stop.
Now here’s a funky tidbit for you - during the Northern Hemisphere winter the stronger westerly winds that build up in the north, combined with frictional drag at the Earth's surface, actually produce a very small, but measurable, increase in the speed of rotation of the Earth. This doesn’t happen in the Southern Hemisphere as there is much less landmass for the wind to drag against.
So there you go, a bit about wind...