LT,

In it's basic form and how it relates to hunting.....A thermal is a mass of rising or sinkingair caused by differing temperatures on the ground.

Thermals always happen they are just more pronounced during fair weather as the time of switching back to solar heatingbegins (about an hour or so just after sunrise) As theincoming solar energy starts to build enough strength to reverse the heat loss effects from terrestrial radiation, the thermals rise.Thisdoes not take intoaccount severeweather, I'm talking about a nice calm day and night with no major weather fronts moving through the area.

Now for hunting I'm talking about thermals that are associated with theradiant and terrestrial heating and cooling cycles. There are other "thermals"that can form throughout the day as a result of heat buildupsand keep in mind that those thermals as they rise cannot leave a vacuum behind them, so air has to move in to replace it around both or one side of the thermal. Youcan also experience lee wind shifts around he thermals as well. These types of "thermals" are more interesting to aviators and para gliders as it effects them way more than us hunters on the ground. Again, my approachconcentratesmore on the the thermals associated (as mentioned) with the solar heatingand terrestrial cooling of the planet. I think about thermals when I hunt hilly terrain, I'll never hunt a stand in the bottoms (hollows) in the evenings when the thermals drop because they tend to settle in the lowest spots first thus bring my scent down with it.

With the diminishing effects of surface radiation through the night, the effects of surface or "solar radiation" start to drop. As surface objects loose their radiant heat (from the sun during the day) it starts to cool thus cooling the air as well. As the aircools it fallsbringing your scent down with it. It should also be noted that somewhere during the early morning period, the radiation balance curve crosses thezero line (a balancebetween gain and loss) and therefore no temperature change.

The time of switching back to solar heatingbegins an hour or so just after sunrise because theincoming solar energy does not yet have enough strength to reverse the heat loss from terrestrial radiation.As a result, the surface and lower atmosphere air are still losing heat for about an hour after sunrise and thus the coldest temperature of the day has yet to be reached. This meansthe time of coldest temperatures areabout an hour after sunrise. Again thisdoes not take into effect weather fronts, I'm talking about a nice calm day and night with no major weather fronts moving through the area.

It's just after this time that the Thermals will start to rise....as the sun heats the earth and radiant heat builds up, the hot air from the surface will rise and theoretically bring your scent up with it away from Mr. Whitetails nose.