<P> While the dry adiabatic lapse rate is a constant 9.8 ° C / km (5.38 ° F per 1,000 ft, 3 ° C / 1,000 ft), the moist adiabatic lapse rate varies strongly with temperature . A typical value is around 5 ° C / km, (9 ° F / km, 2.7 ° F / 1,000 ft, 1.5 ° C / 1,000 ft). The formula for the moist adiabatic lapse rate is given by: </P> <Dl> <Dd> Γ w = g 1 + H v r R s d T c p d + H v 2 r R s w T 2 = g R s d T 2 + H v r T c p d R s d T 2 + H v 2 r ε (\ displaystyle \ Gamma _ (w) = g \, (\ frac (1 + (\ dfrac (H_ (v) \, r) (R_ (sd) \, T))) (c_ (pd) + (\ dfrac (H_ (v) ^ (2) \, r) (R_ (sw) \, T ^ (2))))) = g \, (\ frac (R_ (sd) \, T ^ (2) + H_ (v) \, r \, T) (c_ (pd) \, R_ (sd) \, T ^ (2) + H_ (v) ^ (2) \, r \, \ epsilon))) </Dd> </Dl> <Dd> Γ w = g 1 + H v r R s d T c p d + H v 2 r R s w T 2 = g R s d T 2 + H v r T c p d R s d T 2 + H v 2 r ε (\ displaystyle \ Gamma _ (w) = g \, (\ frac (1 + (\ dfrac (H_ (v) \, r) (R_ (sd) \, T))) (c_ (pd) + (\ dfrac (H_ (v) ^ (2) \, r) (R_ (sw) \, T ^ (2))))) = g \, (\ frac (R_ (sd) \, T ^ (2) + H_ (v) \, r \, T) (c_ (pd) \, R_ (sd) \, T ^ (2) + H_ (v) ^ (2) \, r \, \ epsilon))) </Dd> <Dl> <Dd> <Table> <Tr> <Td> where: </Td> </Tr> <Tr> <Td> Γ w (\ displaystyle \ Gamma _ (w)) </Td> <Td> = Wet adiabatic lapse rate, K / m </Td> </Tr> <Tr> <Td> g (\ displaystyle g) </Td> <Td> = Earth's gravitational acceleration = 9.8076 m / s </Td> </Tr> <Tr> <Td> H v (\ displaystyle H_ (v)) </Td> <Td> = Heat of vaporization of water, = 2501000 J / kg </Td> </Tr> <Tr> <Td> R s d (\ displaystyle R_ (sd)) </Td> <Td> = Specific gas constant of dry air = 287 J kg K </Td> </Tr> <Tr> <Td> R s w (\ displaystyle R_ (sw)) </Td> <Td> = Specific gas constant of water vapour = 461.5 J kg K </Td> </Tr> <Tr> <Td> ε = R s d R s w (\ displaystyle \ epsilon = (\ frac (R_ (sd)) (R_ (sw)))) </Td> <Td> = The dimensionless ratio of the specific gas constant of dry air to the specific gas constant for water vapour = 0.622 </Td> </Tr> <Tr> <Td> e (\ displaystyle e) </Td> <Td> = The water vapour pressure of the saturated air </Td> </Tr> <Tr> <Td> p (\ displaystyle p) </Td> <Td> = The pressure of the saturated air </Td> </Tr> <Tr> <Td> r = ε e / (p − e) (\ displaystyle r = \ epsilon e / (p-e)) </Td> <Td> = The mixing ratio of the mass of water vapour to the mass of dry air </Td> </Tr> <Tr> <Td> T (\ displaystyle T) </Td> <Td> = Temperature of the saturated air, K </Td> </Tr> <Tr> <Td> c p d (\ displaystyle c_ (pd)) </Td> <Td> = The specific heat of dry air at constant pressure, = 1003.5 J kg K </Td> </Tr> </Table> </Dd> </Dl>

What effect does heating an air mass have on its stability