Part III - Atmospheric stability In our discussion so far we have made two assumptions: (i) that certain processes force air to rise from Earth's surface; and (ii) that rising air does not mix substantially with the surrounding atmosphere. Once an initial lifting force ceases, the fate of a rising air parcel depends on the state of the atmosphere through which it rises, or atmospheric stability. Consider the three examples in Figures 3 through 5. In each example the environmental temperature is shown with a solid line, and the parcel temperature follows the dry and wet adiabatic rates of cooling (dashed lines). In each example, the surface temperature is 30 C, surface dew point is 14 C, and the wet adiabatic lapse rate is 5 C km. Weather balloons measure the temperature above Earth's surface. These measurements allow us to calculate the rate at which the surrounding environmental temperature changes with height - the environmental lapse rate (ELR). The atmosphere is considered absolutely stable if an air parcel that is forced aloft cools faster than the surrounding environment (Figure 3), that is, when the parcel rate of cooling (the DARL or WARL) is faster than the ERL. If the force