Got my PPL in October - haven't flown since (money issues). But I am studying for instrument rating. A question occurred to me that I have never thought about. It is regarding barometric pressures. The book says that for every 1000ft, the barometric pressure (with regards to mmHg) changes 1 inch. I get that temperature changes barometric pressure - but wouldn't temperature change that standard rate of change also (1 inch to 1000ft)? Does that ratio hold constant in every column of air? That seems strange to me.