Question

The diameter of circular collecting area of Symon's gauge is ____________.

• A. 30.5 cm
• B. 12.7 cm
• C. 5 cm
• D. 7.7 cm

Hint:

To remember Symon's rain gauge dimensions:
- Collecting diameter = 12.7 cm (5 inches).
- Height of funnel rim above ground = 30.5 cm (1 foot).

Answer 1

The Correct Option is B

Step 1: Understanding the Concept:
Symon's rain gauge is the standard non-recording rain gauge historically used by the India Meteorological Department (IMD) to measure daily rainfall.
It is designed with specific dimensions to ensure standardized, accurate measurements across different weather stations.

Step 2: Detailed Explanation:
Let us examine the physical dimensions of Symon's rain gauge:
- The gauge consists of a circular glass or metal funnel that directs collected water into a receiving bottle.
- The standard diameter of the circular collecting funnel is 5 inches, which is equivalent to 12.7 cm (or 127 mm).
- The receiving bottle has a capacity of about 2 to 3 liters of water, which is equivalent to about 100 mm of rainfall.
- The gauge is installed on a concrete foundation such that the rim of the funnel is exactly 30.5 cm (12 inches) above the ground level to prevent ground splash from entering the collector.
Thus, the diameter of the circular collecting area is 12.7 cm.

Step 3: Final Answer:
The correct option is (B).