Question

The air parcel above has a temperature of 30 deg C on the surface. Its Dew Point temperature is 20 deg C. The dry adiabatic lapse rate is 10 deg C/km and the moist adiabatic lapse rate is 6 deg C/km. An external force lifts the air parcel from the surface to 1 km of altitude. At 1 km the external forcing is removed. What will happen to the air parcel once the external forcing is removed? Will a cloud form?

Answer 1

Once the external force is removed , the air parcel will remain at that level.

Yes a cloud will form

Step-by-step explanation:

Given that:

Temperature of the air parcel
`T_a` = 30 ° C

Dew point temperature = 20 ° C

Dry adiabatic lapse rate D = 10° C/Km

Moist adiabatic lapse rate M= 4° C/Km

external force lifting the air parcel from surface to the attitude = 1 km

Let first calculate the air temperature T at the top of the mountain

T =
`T_a - (D*1 \ km) - (M * 1 \ km)`

T = 30 ° C - ( 10 ° C/Km × 1 km ) - ( 4° C/Km × 1 km )

T = 30 ° C - 10 ° C - 4 ° C

T = 30 ° C - 14 ° C

T = 16 ° C

The temperature at the top of the mountain is 16 ° C

What will happen to the air parcel once the external forcing is removed?

Once the external force is removed , the air parcel will remain at that level.

This is because, from the information given: air temperature will drop to .20° C by the dry adiabatic lapse rate of 10° C/km at an altitude of 1 km.

Since both the air parcel temperature and the external temperature are taking place at 1 km ; then no external force is applied thus, they will remain at that level.

Will a cloud form?

Yes, a cloud will form

GIven that ; the Dew point temperature = 20 ° C , the air parcel will no be able to either sink or rise. Therefore condensation of vapor to water will occur which in turns form a cloud.