The Duckmeister
Has a juicy midrange
Yeah, you're basically right. Surface friction creates a turbulent boundary layer, which means there's a lot of vertical movement within the airflow as well as travelling across the surface. That's how you get gusts, lulls (reduced windspeed) and small shifts of direction. Little pockets of this turbulent flow come bashing down from a great height and spread out as they hit the ground, much like a water balloon, so you get increased wind pressure at the front of the gust, small shifts around the sides as it blows across the "gradient" wind, and a lull, or dead spot behind where there's actually pressure against the gradient wind, causing a slight reduction of wind pressure.
You can see the effects really well on a windy day where the wind is blowing off the shore & onto the water. The land introduces a lot more turbulence than the water does, and there are no waves (unless it's an ocean beach subject to big swells) so it's pretty calm close to shore. If you can get a good vantage point you can see the pockets of air hit the water, spread out & race across. In yachtie terms we call them bullets, 'cos they're small & powerful. Funky stuff. :smile:
