Air Stability And Instability

If stable (unstable) air is forced up or down it has a tendency to return to (continue to move away from) its former position once the motivating force ceases. Figure 5.3 shows the reason for this important characteristic. The environment temperature curve (A) lies to the right of any path curve representing the lapse rate of an unsaturated air parcel cooling dry adiabatically when forced to rise. At any level, the rising parcel is cooler and more dense than its surroundings and therefore tends to revert to its former level. Similarly, if air is forced

Height

Pressure

A Stable case B Unstable case

/tropopause environment curve

A Stable case B Unstable case environment curve

Height

Pressure

Tephigram Unstable Air

Temperature

Figure 5.3 Tephigram showing (A) stable air case - TA is the air temperature and Td the dew-point; and (B) unstable air case. The lifting condensation level is shown, together with the path curve (arrowed) of a rising air parcel. X is the saturation humidity mixing ratio line through the dew-point temperature (see text).

Temperature

Height

Pressure

Height

Pressure

\ ENVIRONMENT

\ CURVE

CONVECTIVE \

Continue reading here: Condensation Levell

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