Correct Answer - Option 1 : Super-adiabatic
Concept:
Environmental Lapse Rate (ELR):
- In the troposphere, the temperature of the ambient air normally decreases with an increase in height. The rate of change of temperature of the ambient air is called environmental lapse rate (ELR) or ambient lapse rate.
- When dry air expands and cools adiabatically the lapse is about 9.8° C per km and known as the adiabatic lapse rate.
- When ELR is greater than the adiabatic lapse rate, the prevailing lapse rate is known as the super-adiabatic lapse rate. In this case, the environment is unstable.
- When ELR is less than the adiabatic lapse rate, the prevailing lapse rate is known as the sub-adiabatic lapse rate. In this case, the environment is stable.
- When the temperature of the ambient air increases with an increase in height, that situation is called an inversion in lapse rate.
Calculation:
Given,
|
Elevation
(m)
|
Temperature
(°C)
|
|
4
|
21.25
|
|
444
|
15.70
|
From the given table, difference in height = (444 – 4) m = 440 m = 0.44 km
and difference in temperature = (15.70 - 21.25) °C
= -5.55 °C.
Hence,
\({\rm{Lapse\;rate\;}} = \frac{{{\rm{difference\;in\;temperature\;}}}}{{{\rm{difference\;in\;height}}}} = {\rm{\;}}\frac{{ - 5.55{\rm{\;}}^\circ {\rm{C}}}}{{0.44{\rm{\;km}}}} = - 12.61^\circ {\rm{C}}/{\rm{km}}\)
The negative sign indicates the temperature decreases with the increase in height.
So, ELR = 12.61° C/km > 9.8° C/km.
Hence the Laps rate is super adiabatic.
