Question

The monsoon winds begin to retreat after mid-October because:
a) The temperature increases and pressure decreases
b) The temperature decreases and pressure increases
c) The north east monsoon winds begins to blow
d) Rainy season begins

Answer 1

Hint: Monsoon or rainy season runs June through September. The season is dominated by the humid southwestern summer monsoon, which starts in late May or early June and steadily sweeps across the region. Monsoon rains begin to recede in early October from North India. Usually, South India gets more rainfall.

Complete answer:
- In the months of October and November, the Monsoon winds begin to withdraw because at this time due to the Southwest motion of the Sun, the Monsoon trough of low pressure over the Ganga Plains becomes weaker. Gradually, the low-pressure trough is replaced by a high-pressure trough, marking the retreat of the monsoon winds.
- The Southwest Monsoon begins its withdrawal from the Pakistani border in Northwest India in the first week of September.
- These winds, therefore, earlier withdraw from the regions where they hit the last. The retreat of these winds is due to the weakening of the northwestern parts of the low pressure area.
- This occurs because of the low temperatures induced by the apparent change of the sun towards the equator and also because of the widespread rains that dramatically bring down temperatures. The air pressure is therefore starting to decrease. Such changes in the atmospheric pressure patterns cause the monsoons of the Southwest to withdraw.
- Hence this time is known as the Southwest monsoon retreat season. By the end of October, the low temperature and low pressure caused these winds to withdraw from most of northern India.

Hence the correct answer is option b).

Note: El Nino, marked by a warming of the Pacific Ocean's surface temperatures, is correlated with India's lower than normal monsoon rainfall. El Nino has a detrimental influence on the summer monsoon, which accounts for more than 70% of annual rainfall, on the migration of moisture-bearing winds from the cooler oceans towards India.