Stability classes V and IV comprise very unstable and unstable
conditions, meaning good vertical mixing in the boundary layer.
They do not occur during night-time. Class V occurs only between
May and September.
Stability classes III/2 and III/1 are classified as neutral. III/2 occurs
predominantly at daytime, III/1 predominantly at nighttime
and during sunrise and sunset. These classes are typical
for cloudy and/or windy conditions.
Stability classes II and I comprise stable and very stable conditions,
mostly, but not exclusively at night. They occur with
reduced vertical mixing; horizontal transport over long distances
is possible.