Indian Monsoon

The Arabian Sea branch strikes the Western Ghats and gives heavy rainfall. Rainfall is high on the windward side.

A large part of Indian agriculture depends on monsoon rainfall. Good rainfall supports crops.

India's main rainfall occurs during the south-west monsoon period. This period is generally from June to September.

The south-west monsoon is generally active from June to September. Most of India's rainfall occurs in this period.

The withdrawal of the monsoon is generally associated with the autumn season. In India, the southwest monsoon starts retreating from northwestern India in September, and the retreating-monsoon conditions are prominent during October–November. Summer is more closely associated with the onset and active phase of the monsoon, not its withdrawal. Exam tip: Remember September to November as the broad period of monsoon withdrawal or retreating monsoon.

The retreating monsoon gradually withdraws from northern India toward the south. This is a feature of monsoon withdrawal.

The retreating, or northeast, monsoon is especially important for the southeastern coast of India. During the later part of the year, winds reverse direction and move toward the northeast. While crossing the Bay of Bengal, they collect moisture. These winds then bring rain to Tamil Nadu and nearby southeastern areas, making this season important for that region.

Option B is correct because the Tamil Nadu coast receives substantial rainfall from these moisture-bearing winds, particularly in October and November. The Kachchh coast is mainly associated with other rainfall patterns, while the Konkan and Malabar coasts receive much of their rain from the southwest monsoon. Therefore, Tamil Nadu is the appropriate coastal region.

Monsoon rainfall can vary in timing and amount. Therefore it is called seasonal and irregular.

Deficiency or delay of monsoon can affect crops. Therefore monsoon is very important for farmers.

During the monsoon period rainfall sometimes pauses. This is called a break in monsoon.

At the arrival of monsoon heavy rain may begin suddenly. This is called the burst of monsoon.

Moist winds of the Arabian Sea branch strike the Western Ghats. This gives heavy rainfall on the windward slope.

The rain shadow effect explains why some areas of the Deccan Plateau receive less rainfall. Moist winds from the Arabian Sea are forced to rise when they meet the Western Ghats. They cool and release much of their moisture on the windward western side. After crossing the mountains, the air descends on the leeward eastern side and becomes relatively drier. This sheltered area is called a rain shadow region. Hence option A is correct. The other options do not describe the physical reason for low rainfall there.

Low rainfall in the Deccan is therefore not caused by a polar location, sea ice or absence of sunlight. The plateau is in the tropics and receives sunlight, but the arrangement of the Western Ghats affects the distribution of monsoon rain. Rainfall also varies within the plateau, so the question wisely says some parts. The correct reasoning is based on relief and wind direction: the windward side gets more rain, while the leeward side may remain comparatively dry.

Meghalaya receives very heavy rainfall from monsoon winds. Mawsynram is famous for very high rainfall.

Mawsynram is counted among the world's very high rainfall places. It is located in Meghalaya.

The Aravalli Range lies almost parallel to the south-west monsoon winds. Therefore, the moisture-laden winds are not compelled to rise along the mountain slopes, cool, and condense, resulting in low rainfall in the Thar Desert. Option C is incorrect because the Thar is not close to the sea; it lies far inland. Exam tip: Mountains perpendicular to moisture-laden winds usually receive more orographic rainfall.

Indian monsoon winds pick up water vapour while passing over warm seas and oceans. Heat and moisture from the sea surface provide the energy and water vapour needed for monsoon rainfall. The Himalayas help by blocking the winds and causing rainfall, but they are not the main source of moisture. Exam tip: Link monsoon rainfall with evaporation from warm seas.

During summer, the south-west monsoon winds blow over India. They carry moisture from the Indian Ocean, the Arabian Sea and the Bay of Bengal, bringing rainfall to most parts of the country. North-east winds are mainly associated with the winter monsoon, so they are not correct here. Exam tip: Remember that summer rainfall is linked with the south-west monsoon, while winter monsoon winds are north-easterly.

During winter, high pressure develops over northern and interior India. Winds therefore generally blow from land towards the sea, that is, from the north-east towards the south-west. These north-east winds are usually dry, though they may bring rain to the Tamil Nadu coast after picking up moisture from the Bay of Bengal. Winds from the south-west towards land are associated with the summer monsoon. Exam tip: remember north-east winds for winter and south-west winds for summer.

Tamil Nadu receives rain from the north-east or retreating monsoon. Therefore it is known for winter rainfall.