Help - Mid-Level Lapse Rates

Mid-Level Lapse Rates (C km^-1)

A lapse rate is the rate of temperature change with height. The faster the temperature decreases with height, the "steeper" the lapse rate and the more "unstable" the atmosphere becomes.

Lapse rates are shown in terms of degrees Celcius change per kilometer in height. Values less than 5.5-6.0 C km^-1 ("moist" adiabatic) represent "stable" conditions, while values greater than 9.8 C km^-1 ("dry" adiabatic) are considered "absolutely unstable." In between these two values, lapse rates are considered "conditionally unstable." Conditional instability means that if enough moisture is present, lifted air parcels could have a negative LI (lifted index) or positive CAPE.

The 700-500 mb lapse rates, also referred to as mid-level lapse rates, are meant to identify regions where deep convection is more probable (all else being equal). Likewise, steeper lapse rates correspond to the possibility of larger CAPE and stronger storm updrafts.