The troposphere is the lowest portion of 0), then when a parcel of air rises and expands, it'll arrive at the new height at a lower temperature than its surroundings. In this case, the air parcel is denser than its surroundings, so it sinks back to its original height, and the air is stable against being lifted. If, on the contrary, the upper air is cooler than predicted by the adiabatic lapse rate, then when the air parcel rises to its new height it'll have a higher temperature and a lower d… (More on Troposphere)