Conditional Instability - 5km and above

  • note Tp > Te
  • A: it will rise on its own since now it is less dense than the surrounding environmental air
  • The height where Tp becomes equal to and then larger than Te is called the level of free convection
  • the parcel is still rising moist adiabatically (6C km-1)
  • the parcel will continue to rise until:
    • Tp = Te
  • above that point, Tp < Te , so the parcel will rise no further
  • so, below 4 km where Tp < Te , the atmosphere is stable to parcel movement
  • above 4 km where Tp > Te , the atmosphere is unstable to parcel movement
  • this is an example of a conditionally unstable atmosphere... the condition is lifting the parcel above 4 km where it can then rise on its own

It's important to realize that the current state of the atmosphere can be comprised layers with different stabilities..... let's look at an example