Question

According to IMD, a day is called as rainy day if the minimum amount of rainfall during a period of 24 hours is:

• A. 2.5 cm
• B. 5.0 cm
• C. 0.25 cm
• D. 0.75 cm

Hint:

Do not confuse "rainy day" (2.5 mm) with "crop rainy day" (5.0 mm).
A crop rainy day is the minimum rainfall required to be agriculturally effective for crop growth.

Answer 1

The Correct Option is C

Step 1: Understanding the Concept:
Meteorological departments establish standardized definitions for weather events to ensure consistent climate data collection.
The India Meteorological Department (IMD) defines a "rainy day" based on the minimum depth of rainfall measured in a rain gauge over a 24-hour period.

Step 2: Detailed Explanation:
According to the official definitions used by the India Meteorological Department:
A "rainy day" is defined as any 24-hour period (typically measured from 08:30 IST to 08:30 IST the next day) during which the recorded rainfall is:
\[ 2.5 \text{ mm or more} \] Let us convert this value from millimeters to centimeters:
\[ 2.5 \text{ mm} = \frac{2.5}{10} \text{ cm} = 0.25 \text{ cm} \] If the recorded rainfall is less than 2.5 mm (0.25 cm), it is classified as a "non-rainy day" or "trace" rainfall, as such small amounts evaporate quickly and do not contribute significantly to soil moisture or runoff.
Other classifications include:
-Crop rainy day: Rainfall of 5.0 mm or more.
-Heavy rainfall day: Rainfall exceeding 64.4 mm.

Step 2: Final Answer:
According to the IMD, a day is classified as a rainy day if the rainfall recorded in 24 hours is at least 0.25 cm (2.5 mm).