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Q110
(NDA-I/2024)
Geography › World Physical Geography
Official Key
Which of the following statements regarding air temperature is/are correct ? 1. Air temperature is measured at a standard height of 1·2 m (4·0 feet) above the ground surface. 2. The average rate of temperature decrease with height is termed as the environmental temperature lapse rate. Select the answer using the code given below :
Explanation
Both statements are correct according to standard meteorological practices:
- Statement 1: To obtain an accurate reading of the ambient air temperature and minimize the influence of direct solar radiation or heat reflected from the ground, thermometers are placed in a Stevenson Screen. The standard height for these measurements, as prescribed by the World Meteorological Organization (WMO) and followed by the India Meteorological Department (IMD), is approximately 1.2 meters (4 feet) to 2 meters above the ground surface.
- Statement 2: The Environmental Lapse Rate (ELR) is defined as the rate at which the temperature of the stationary atmosphere decreases with an increase in altitude. In the troposphere, the temperature generally drops as one moves higher; the average or 'normal' lapse rate is approximately 6.5°C per kilometer.
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