Define the difference between thermals and wind. Air movement is air movement to me...
Disclaimer: I’m not a scientist, I may completely screw this up technically. But I believe the practical implications remain.
Wind moves generally horizontally across the earth’s surface, while thermals move generally vertically as the earth’s surface warms or cools. That’s not completely cut and dry because either will follow the lay of the land somewhat, at least in hilly or mountainous terrain. I wouldn’t know what thermals are like in flat terrain.
The practical difference, to me, is that thermals are more predictable and consistent. Wind can get pretty screwy as it follows terrain. For example, wind tends to swirl in lower lying areas, whereas it’s generally more consistent closer to the tops of surrounding ridges. On an evening hunt, I may have no idea what wind will be doing in a particular bottom, but I know that as that bottom loses daylight and the ground cools (or ceases to warm) thermals will be falling. That affects where and when I can hunt.
On days with light or no wind, which we have a lot of where I live and hunt, thermals are the primary thing to be concerned with as far as keeping my scent away from animals. Say I have a 3 mph west wind for a morning hunt, and I’m planning to hunt the upper 1/3 of the east side of a north-south running ridge, I don’t want to get there too early (before daylight) or thermals will be falling, that light wind will be coming over the top and tumbling down the ridge, and I’m expecting deer to move low to high. But once that east face starts to warm up, and those thermals shift to pulling up the ridge, they’re likely stronger than that light wind. In other words, the thermals give me an advantage whereas a cursory glance at wind direction on a forecast would have painted a different picture.
I agree with your point that air movement is air movement, and my reply was more in response to the post I quoted than to the OP’s question about distance. My point is just that regardless of what we’re hunting, a person probably can’t get by consistently ignoring thermals and only paying attention to wind. They can be doing different things on the landscape, and in some circumstances thermals are the primary concern.
