I am having trouble with differentiating between what seems to be two phenomena in the atmosphere. Maybe someone could comment on it. Here is an explanation of the problem. 1) An air mass has an inherent pressure due to its temperature. Relatively cold air masses have relatively high atmospheric pressures associated with them because the denser air has more mass in it per cubic unit, causing any point on the surface of the earth to bear more weight from the gravitational pull on that mass. Relatively warm air masses have a relatively low atmospheric pressures associated with them because the air is relatively less dense and so there is less mass to be pulled by gravity against each square unit on the surface of the earth. (Correct me if this understanding is incorrect.) 2) Low pressure areas also develop in areas of relatively warm air because the rising warm air causes a low pressure below it as it draws matter upward out of the space below it. I believe this is true at the equator among other places. Which of these would describe the pressure gradient that causes wind. It seems clear to me that the second one would be responsible for some kind of wind simply because air is drawn into the low pressure area that is formed by the rising warm air. This moving air would of course be wind. But I have read that air masses tend not to mix. (This non-mixing provides the opportunity for fronts and precipitation.) So, it does not seem that when speaking of air masses in terms of their inherent pressure as described in #1, that wind could flow from a cooler (higher pressure) air mass to a warmer (lower pressure) air mass without mixing going on. In both of these I know that I am ignoring the Coriolis effect and cyclonic action and all. I simply would like someone to point out if I am not understanding the matters of high and low pressure areas correctly.