Stability of air
Can anyone explain why the answer to the below question is b) unstable please?
The air between 1000ft and 2000ft at 55N 0730W (attached) can be described as:
a) Stable
b) Unstable
c) Neutrally stable
d) Conditionally unstable
I thought it is a) stable, because the parcel of air has 'lapsed' at 4c per 1000ft. This is the dry lapse rate. The environmental lapse rate for the same 1000ft is 1.98c. Because 4c is greater than 1.98c, the parcel of air will sink relative to the environment. Therefore it is stable. Or so I thought...