Atmospheric Atmospheric MoistureMoisture

Lapse Rate

By K. Y. NG

101055 Temp. °CTemp. °C00-5-5-10-10-15-15

20002000

15001500

10001000

500500

Height (m)Height (m)

CondensationCondensationLevelLevel

DALRDALR 10°C / 10°C / 1000 m1000 m

SALRSALR5°C / 5°C / 1000 m1000 m

Dry Adiabatic Lapse Rate & Saturated Adiabatic Lapse Rate

Dry Adiabatic Lapse Rate & Saturated Adiabatic Lapse Rate

500500m: 5°Cm: 5°C

20002000m: -2.5°Cm: -2.5°C

101055 Temp. °CTemp. °C00-5-5-10-10-15-15

20002000

15001500

10001000

500500

Height (m)Height (m) StabilityStability

ELR (1) ELR (1) 4°C /4°C /1000m1000m

SALRSALR

DALRDALR

CondensationCondensationLevelLevel

20002000m: 2°Cm: 2°C20002000m: -2.5°Cm: -2.5°C

Rising air parcel is Rising air parcel is coldercolder than surrounding than surrounding airair (-2.5 °C (-2.5 °C < 2 °C)< 2 °C). The air parcel sinks . The air parcel sinks back to its starting point, i.e. back to its starting point, i.e. STABILITYSTABILITY ELR (1) < SALR < DALRELR (1) < SALR < DALR

101055 Temp. °CTemp. °C00-5-5-10-10-15-15

20002000

15001500

10001000

500500

Height (m)Height (m) InstabilityInstability

ELR (2) ELR (2) 12°C /12°C /1000m1000m

SALRSALR

DALRDALR

CondensationCondensationLevelLevel

20002000m: -14°Cm: -14°C

20002000m: -2.5°Cm: -2.5°C

Rising air parcel is Rising air parcel is warmerwarmer than surrounding than surrounding airair (-2.5 °C (-2.5 °C > -14 °C)> -14 °C). The air parcel will . The air parcel will rise continuously, i.e. rise continuously, i.e. INSTABILITYINSTABILITY ELR (2) > DALR >SALRELR (2) > DALR >SALR

101055 Temp. °CTemp. °C00-5-5-10-10-15-15

20002000

15001500

10001000

500500

Height (m)Height (m)

ELR (3) ELR (3) 8°C /8°C /1000m1000m

SALRSALR

DALRDALR

CondensationCondensationLevelLevel

20002000m: -6°Cm: -6°C20002000m: -2.5°Cm: -2.5°C

Below 850m, as the air parcel is Below 850m, as the air parcel is cooler than the surrounding aircooler than the surrounding air (DALR & SALR > ELR (3) )(DALR & SALR > ELR (3) ), the , the air parcel will sink normally, i.e. air parcel will sink normally, i.e. stable air.stable air.

IFIF the air parcel is the air parcel is forced to forced to rise above 850m,rise above 850m, it will be it will be warmer than the surrounding warmer than the surrounding airair (SALR < ELR (3) ) (SALR < ELR (3) ). The . The air parcel will rise air parcel will rise continuously, i.e. continuously, i.e. unstable air.unstable air.

850850mm

Conditional InstabilityConditional Instability

UNSTABLE AIRUNSTABLE AIR

STABLE AIRSTABLE AIR

CONDITIONAL INSTABILITYCONDITIONAL INSTABILITY

Conclusion

A ir S ta b ility a n d In s ta b ility

E L R < S A L R < D A L Ri.e .

A ir S ta b ility

E L R > D A L R > S A L Ri.e .

A ir Insta b ility

S A L R < E L R < D A L Ri.e .

C o nd it io na l Insta b ility

W he n the p a r c e l o f a ir is fo r c e d to up lift ,(O r o g r a p hic , F o nta l o r C o nv e c t iv e up lift )the te m p e r a tur e o f it d e c r e a se s in he ig hta c c o r d ing to the A d ia b a t ic L a p se R a te .

THE ENDTHE END