GATE 2023 CE (CE2) – Question 34
For the elevation and temperature data given in the table, the existing lapse rate in the environment is ______ °C/100 m (round off to two decimal places).
| Elevation from ground level (m) | Temperature (°C) |
|---|---|
| 5 | 14.2 |
| 325 | 16.9 |
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Correct answer: -0.85 to -0.83
Explanation
**Environmental lapse rate** is the rate at which the actual air temperature falls with height:
$$\Gamma=-\frac{dT}{dz}.$$
**Step 1: change between the two readings.**
$$\Delta T=16.9-14.2=+2.7\ ^\circ\text{C},\qquad\Delta z=325-5=320\text{ m}.$$
**Step 2: per 100 m.**
$$\Gamma=-\frac{2.7}{320}\times100=-0.84375\approx\mathbf{-0.84\ ^\circ C/100\ m}.$$
The negative sign means the temperature **rises** with height here, a temperature inversion.