In nature, air cools as it rises. If no heat is added to this process, it is cal
ID: 802842 • Letter: I
Question
In nature, air cools as it rises. If no heat is added to this process, it is called "adiabatic". Adiabatic cooling of the atmosphere occurs at a rate of 10 degree C for every 1000m increase in height, so long as the air parcel remains unsaturated(dry). That is why it is called the dry adiabatic lapse rate. Calculate the temperature of an unsaturated air parcel at 100m increments as it rises from the Earth's surface. The surface temperature is 35 degree C. Rising air parcels can eventually cool to the dew-point temperature. When this happens, the parcel becomes saturated and condensation begins (clouds form). The height where this occurs is called the lifting condensation level (LCL). If the parcel continues to rise past the LCL, it cools at a slower rate. This is because the condensation process releases heal into the parcel(warming) as it continues to rise(cooling). The wet adiabatic lapse rate varies between 5 degree C/1000m and 9 degree C/1000m depending on the amount of moisture in the air in question. Fill in the temperature column for parcel "A". The LCL for pared "A" is 1.5fcm. After which the wet adiabatic lapse rate is 5 degree C/1000m. Fill in the temperature column for pared "B". The LCL for parcel "B" is 1.5km. After which the wet adiabatic lapse rate is 7 degree C/1000m.Explanation / Answer
4. Since the parcel of the air is saturated so it will cool according to the dry adiabatic rate i.e. 10 degree rise for every 1000 m or 1 degree rise for every 100m.
Height (m) Temperature ( degree celsius)
1000 25
900 26
800 27
700 28
600 29
500 30
400 31
300 32
200 33
100 34
surface 35
5. The air parcel at A will initially be unsaturated so it will rise according to dry adiabatic rate. After it reaches the lifting condensation level i.e 1.5 km it will become saturated and will rise accoding to the wet adiabatic rate which is 5 degree celsius/1000m or 2.5 degree/500m
6. Similarly the air parcel at B will rise initially with dry adiabatic rate. After attaining the lifting condensation level it will cool according to the wet adiabatic rate i.e. 7 degree celsius per 1000 m or 3.5 degree/500m.
Parcel A temperature( degree celsius) height( km) Parcel B temperature( degree celsius)
-2 5 -26
0.5 4.5 -22.5
3 3.5 -19
5.5 3.0 -15.5
8 2.5 -12
10.5 2.0 -8.5
13 1.5 -5
18 1.0 0
23 0.5 5
28 surface 10
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