Explanation of Assertion and Reason

This question asks to evaluate an Assertion (A) and a Reason (R) concerning the retreating monsoon in Northern India and determine their truthfulness and relationship.

Analyzing Assertion (A)

• Assertion (A): The retreating monsoon winds are associated with dry weather and clear skies in northern India.
• Assessment: This statement is true. The retreating monsoon period (typically October to December) sees a decrease in rainfall and clear, dry weather conditions in most parts of Northern India as the monsoon winds move away from the region.

Analyzing Reason (R)

• Reason (R): During the retreating monsoon, the low-pressure area over the northern plains is replaced by a high-pressure system.
• Assessment: This statement is also true. As the apparent movement of the sun shifts southwards, the intense heat over the northern plains decreases, causing the summer low-pressure trough to weaken and be replaced by a region of higher atmospheric pressure.

Evaluating the Relationship

• The shift from a low-pressure system to a high-pressure system over Northern India during the retreating monsoon is the primary reason for the withdrawal of moisture-laden winds.
• The high-pressure system facilitates the outflow of cooler, dry continental air, leading to the dry weather and clear skies mentioned in Assertion (A).
• Therefore, Reason (R) correctly explains Assertion (A).

Conclusion

Since both Assertion (A) and Reason (R) are true statements, and Reason (R) provides the correct scientific explanation for Assertion (A), the correct option is the one that states this.

Selected Option: Both A and R are true, and R is the correct explanation of A.