Environmental Temperature Lapse Rates


The rate of change in temperature with height between mandatory pressure levels (850-700 mb and 700-500 mb), or fixed layers above ground level (Sfc-3km and 3-6km). A dry adiabatic temperature profile will have lapse rates near 9.6 C/km, while the moist adiabatic lapse rate is near 6 C/km. Lapse rates greater than 9.6 C/km are said to be "superadiabatic" or "absolutely unstable", lapse rates between dry and moist adiabatic are "conditionally unstable", and lapse rates less than moist adiabatic are "absolutely stable".

Conditionally unstable lapse rates in the mid troposphere are necessary for deep convection, while low-level lapse rates will often become superadiabatic during the afternoon near the ground. If the lapse rates are "steep" from the surface to 3 km AGL, then convective inhibition is usually weak and thunderstorm development could occur (given sufficient moisture).