DirtyBear0311
Well-Known Member
Could someone please explain to me exactly what thermals are.? I have a very basic understanding of them but I would like to know their affect on hunters and if they only exist in hilly country or flat land too.
thermals
- Thread starter DirtyBear0311
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catman529
Well-Known Member
I also have a very basic understanding but what I know is that a thermal is a rising column of air that can stem off of features in the terrain and I can't remember what causes them but I know that birds use them a lot and they are fun to fly an RC plane into as well. You will see vultures and other birds flying around in circles without flapping their wings because they are riding a thermal to keep altitude without using much energy.
I think thermals can be anywhere, hilly or flat. I once asked a hot air balloon pilot friend of mine, why they don't fly in the middle of the day. He said the thermals were too intense for a hot air balloon.
As far as it affects hunters, I wish I could say but I have never considered them while hunting.
I think thermals can be anywhere, hilly or flat. I once asked a hot air balloon pilot friend of mine, why they don't fly in the middle of the day. He said the thermals were too intense for a hot air balloon.
As far as it affects hunters, I wish I could say but I have never considered them while hunting.
bigtex
Well-Known Member
A simple way to explain it would be that air rises in the morning and falls in the evening. On a calm morning when it's warming up the air will rise causing an updraft of air moving to the tops of hills, ridges, etc. In the evening the air cools, the cooler air sinks back toward the hollers.
BSK
Well-Known Member
Thermals are winds driven by differences in air temperature. Warm air is lighter/thinner, hence rises (think of a hot-air balloon). Cooler air is denser/thicker, hence falls.
Thermals can occur in flat country. Bare ground absorbs heat much faster than forested or grassy areas. That bare ground also radiates more heat, warming the air just above the ground, which then rises. As that warmer air rises, surrounding air is drawn in from all directions to replace the rising air. Late in the morning, once the sun has had a chance to hit the ground for an hour or so, this differential heating process can produce light thermal winds being drawn into an open dirt field from the surrounding areas.
Although thermal winds will be produced anywhere differential heating of the surface occurs, thermals are most pronounced and obvious in hilly terrain. When the sun first peaks over the horizon, the suns rays hit the tops of ridge-lines first. The ground is warmed there, which warms the air just above it, and that air begins to rise. This rising air must be replaced, and air is drawn up out of the valleys, with air on the east (sunny-side) of the ridge rising most rapidly. This thermal wind rising up to and verically away from the top of the ridge aids both bucks near the rut and the hunter in the early morning hours. Bucks can walk the ridge-lines and scent-check for does in the valleys. Hunters hunting on ridge-lines can have their scent lifted vertically away from them producing a situation with literally no "downwind."
In hilly terrain, exactly the opposite occurs once the sun sets. Without the sun heating the ground, air begins to cool and settle. The coolest air settles the quickest, and begins to run downhill just like water. Imagine a "river" of the coolest air running down every drainage and concentrating in the bottoms of valleys. These evening thermal can become amazingly strong, often reaching 5-10 MPH, but can also be amazingly thin, only reaching 10-15 feet off the ground.
Of course, all of these thermal events can be heavily influenced by pressure system winds (winds driven by high and low pressures systems). Moderate to strong prevailing winds can over-power these thermals. Thermals are the most predictable under High pressure when prevailing winds are virtually nil. The mixture of thermals and prevailing winds are most confusing when prevailing winds are light.
Thermals can occur in flat country. Bare ground absorbs heat much faster than forested or grassy areas. That bare ground also radiates more heat, warming the air just above the ground, which then rises. As that warmer air rises, surrounding air is drawn in from all directions to replace the rising air. Late in the morning, once the sun has had a chance to hit the ground for an hour or so, this differential heating process can produce light thermal winds being drawn into an open dirt field from the surrounding areas.
Although thermal winds will be produced anywhere differential heating of the surface occurs, thermals are most pronounced and obvious in hilly terrain. When the sun first peaks over the horizon, the suns rays hit the tops of ridge-lines first. The ground is warmed there, which warms the air just above it, and that air begins to rise. This rising air must be replaced, and air is drawn up out of the valleys, with air on the east (sunny-side) of the ridge rising most rapidly. This thermal wind rising up to and verically away from the top of the ridge aids both bucks near the rut and the hunter in the early morning hours. Bucks can walk the ridge-lines and scent-check for does in the valleys. Hunters hunting on ridge-lines can have their scent lifted vertically away from them producing a situation with literally no "downwind."
In hilly terrain, exactly the opposite occurs once the sun sets. Without the sun heating the ground, air begins to cool and settle. The coolest air settles the quickest, and begins to run downhill just like water. Imagine a "river" of the coolest air running down every drainage and concentrating in the bottoms of valleys. These evening thermal can become amazingly strong, often reaching 5-10 MPH, but can also be amazingly thin, only reaching 10-15 feet off the ground.
Of course, all of these thermal events can be heavily influenced by pressure system winds (winds driven by high and low pressures systems). Moderate to strong prevailing winds can over-power these thermals. Thermals are the most predictable under High pressure when prevailing winds are virtually nil. The mixture of thermals and prevailing winds are most confusing when prevailing winds are light.
DirtyBear0311
Well-Known Member
Ok great. Thanks for the information and input everyone. I think that I know better understand thermals and will be able to better incorporate them into my overall strategy.
