Question

How would you describe the stability of the atmosphere if you noted a dry adiabatic rate of 10ºC/1000 meters, a wet adiabatic rate of 6.5ºC/1000 meters, and an environmental lapse rate of 7.8ºC/1000 meters?

Answer 1

Answer:

conditionally unstable

Explanation:

Given environmental lapse rate (ELR) = 7.8°C/1000 m

Wet adiabatic lapse rate (WALR) = 6.5°C/1000 m  

Dry adiabatic lapse rate (DALR) = 10°C/1000 m  

The stability of the atmosphere can be described in three ways which are;  

a.      Absolutely stable atmosphere: Here the lifted air whether saturated or unsaturated is colder and hence heavier than the surrounding air and it would return to its initial potion when released. In this case the lifted air will descent back to its original position. It occurs when WALR is greater than ELR.  

b.     Absolutely unstable: here both saturated (and moist) and unsaturated (dry) air parcels are warmer than the surrounding and hence lighter. This means both moist and dry air parcels will rise continuously when released. This occurs when DALR is less than ELR.  

c.      Conditionally unstable atmosphere: This occurs where moist air is unstable while dry air is stable. That is moist or saturated air is warmer than the surrounding and hence it will continuously rise when released while dry air is colder than the surrounding and hence it will descent back to its original position when released.  It occurs when DALR is greater than ELR and ELR is greater than WALR (DALR>ELR>WALR).  

The situation given in the question is "c". 10°C/1000 m > 7.8°C/1000 m > 6.5°C/1000 m

Answer 2

Answer:

conditional instability (Γd >  Γe > Γw)

Explanation:

Given;

dry adiabatic rate, Γd = 10ºC/1000 meters

wet adiabatic rate, Γw= 6.5ºC/1000 meters

environmental lapse rate, Γe = 7.8ºC/1000 meters

Stability of the atmosphere can be described as Absolute stability, Absolute instability or conditional instability.

Conditions for Absolute stability:

Γd > Γw > Γe

Conditions for Absolute instability:

Γe > Γd > Γw

Conditions for conditional instability:

Γd >  Γe > Γw

Thus, conditional instability satisfies the given values of the atmospheric condition: Γd (10) > Γe (7.8) >  Γw (6.5)