Consider a parcel of air at an altitude of 1000 m. It will have the same pressure and temp...

Consider a parcel of air at an altitude of 1000 m. It will have the same pressure and temperature as the air surrounding it, say 18°C. Suppose that the prevailing lapse rate at the time is + 2°C per 100 m. If the air parcel rises to an altitude of 1100 m, how will its temperature compare to that of the surrounding air? Will the parcel of air continue to rise, or will it tend to descend? Why? What would happen if the parcel of air moved to a lower altitude, say 800 m? Would you say that the atmosphere was stable under these conditions? Make a sketch similar to Figure to illustrate your answer.

FIGURE

Illustration of unstable atmospheric conditions, when the environmental lapse rate (e.g., –2° per 100 m) exceeds the adiabatic lapse rate. In this example, buoyant forces keep the air parcels moving in a vertical direction.