If ∂θ/∂z = 0, the atmosphere is said to be neutral,or neutrally stratified, and the lapse rate is equal to the dry adiabatic lapse rate (DALR) Γd ~= 10 K km-1 i.e. the

temperature decreases by 10 K every km.

If ∂θ/∂z > 0, i.e. θ increases with height, the atmosphere is said to be stable, statically stable, or stably stratified.If an air parcel is moved upwards adiabatically, it will follow the DALR, so be colder (therefore denser) than its environment and so sink back down. Conversely if an air parcel is moved downwards adiabatically, it will follow the DALR, so be warmer (therefore less dense) than its environment and so rise back up. In other word, the atmosphere is stable to small perturbations.

If ∂θ/∂z < 0, i.e. θ decreases with height, the atmosphere is said to be unstable, statically unstable, or unstably stratified.

If an air parcel is moved upwards adiabatically, it will follow the DALR, be warmer (less dense) than its environment and so keep on rising. Conversely if an air parcel is moved downwards adiabatically, it will follow the DALR, so be cooler (therefore denser) than its surroundings and so carry on sinking. In other word, the atmosphere is unstable to small perturbations.

If ∂θ/∂z = 0, the atmosphere is said to be neutral,or neutrally stratified, and the lapse rate is equal to the dry adiabatic lapse rate (DALR) Γd ~= 10 K km-1 i.e. the

temperature decreases by 10 K every km.

If ∂θ/∂z > 0, i.e. θ increases with height, the atmosphere is said to be stable, statically stable, or stably stratified.

If ∂θ/∂z < 0, i.e. θ decreases with height, the atmosphere is said to be unstable, statically unstable, or unstably stratified.

The lines are isotherms (lines of constant temperature) and isobars (lines of constant pressure)

plus isentropes (lines of constant potential temperature), also known as dry adiabats.

plus saturated adiabatics (lines of constant equivalent potential temperature).

plus lines of constant mixing ratio r = mass of water vapour/mass of dry air (usually written in g/kg)

Plus the international standard atmosphere.

Plus a radiosonde sounding from Arizona, wind barbs are shown on the right, each full barb is 10 knots.