This set of Air Pollution Control Multiple Choice Questions & Answers (MCQs) focuses on “Adiabatic and Environmental Lapse Rate”.
1. What is meant by the decrease in temperature with altitude?
a) Lapse rate
b) Rate of change of temperature
c) Adiabatic lapse rate
d) Rate of decrease in temperature
View Answer
Explanation: Temperature fall with altitude is termed lapse rate. The adiabatic lapse rate is a specific lapse rate when the ‘air parcel’ does not exchange energy with the surrounding atmosphere.
2. In the troposphere, how does the temperature vary with altitude?
a) Exponentially
b) Linearly
c) The relationship is undetermined
d) It is constant
View Answer
Explanation: In the troposphere, the temperature varies linearly with altitude. This temperature dependence changes in the lower stratosphere, where the temperature remains constant with height.
3. What is the numerical value of the environmental lapse rate?
a) 6.5 degree Celsius per 1000 km
b) 9.8 degree Celsius per 1 km
c) 6.5 degree Celsius per 1000 m
d) 0.98 degree Celsius per 1 m
View Answer
Explanation: The value of the environmental lapse rate (in the troposphere) is calculated to be about 6.5 degree Celsius per 1000 metres. This value indicates that the temperature falls by 6.5 degrees Celsius with every 1000 metre rise in altitude.
4. Which of the following statements about the environmental lapse rate is true?
a) Temperature is always constant
b) Rate is constant always
c) It is negative always
d) It is not constant all the time
View Answer
Explanation: The environmental lapse rate is not always constant. In the lower stratosphere, there the relationship deviates from the 6.5 deg C/1000 m. It is positive perpetually in the upper atmosphere only, where the temperature is constant in the lower stratosphere.
5. Why does the lapse rate vary from the standard in the lower troposphere?
a) Because of the earth’s radiation
b) Because temperature varies
c) Because of weather
d) Because of pressure variations
View Answer
Explanation: The lapse rate usually varies linearly, but it not always the case. This statement is true for a couple of reasons: one is that the radiation from the earth’s surface; and the other being the nature of the earth’s surface.
6. When is the environmental lapse rate most likely to vary from the norm of 6.5 degree Celsius per 1 kilometre?
a) On rainy days
b) On sunny days
c) On cold days
d) It does not deviate
View Answer
Explanation: The environmental lapse rate is most likely to deviate from the standard on sunny days. The earth’s surface radiates more heat on such days, which causes the lapse rate to change. It may be as high as 10 degree Celsius per 1000 m. This deviation, though, is confined to 200 m above the surface.
7. Negative lapse rate can occur in the lower troposphere.
a) True
b) False
View Answer
Explanation: Negative lapse rate can occur in the lower troposphere. However, it only occurs in extreme weather conditions. Under such conditions, the temperature rises with altitude.
8. Which of the following is an assumption made to derive the equation for the lapse rate?
a) Adiabatic process
b) Isochoric conditions
c) Isobaric conditions
d) Air is assumed to be an ideal gas
View Answer
Explanation: To derive the expression of the lapse rate, the air is assumed to be an ideal gas. Additionally, the process is considered to be isothermal. The adiabatic lapse rate is a specific condition of lapse rate.
9. For a polytropic atmosphere, what is the expression of lapse rate? (R is the gas constant, T is the temperature, z is the altitude)
a) (dT/dz) = -(g/R)
b) (dT/dz) = ((n-1)/n)(g/R)
c) (dT/dz) = -((n-1)/n)(g/R)
d) (dT/dz) = -(n/(n-1))(g/R)
View Answer
Explanation: A polytropic atmosphere is given by the formula PVn = C; here, n is the polytropic index, and C is a constant. The lapse rate definition is given as follows:
(dT/dz) = -((n-1)/n)(g/R)
The negative sign indicates that temperature falls with an increase in altitude. ‘n’ is the polytropic index.
10. What is the polytropic index for the environmental lapse rate?
a) 1
b) 1.23
c) 5.51
d) 2.4
View Answer
Explanation: For environmental lapse rate, dT/dZ = 6.5 degree Celsius / 1000m
We know that, (dT/dz) = -((n-1)/n)(g/R)
Here, R (gas constant), and g (acceleration due to gravity) are constants.
n = 1.23
Sanfoundry Global Education & Learning Series – Air Pollution Control.
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