Indian Climate and Seasons

Statement 1 is correct: India experiences winter monsoon due to two reasons: 1) Influence of western disturbances in the North-West India. 2) Influence of permanent North-East trade winds in South-East India along the Coromandel Coast.

Statement 2 is also correct: Monsoons are seasonal winds that change their directions with respect to the temperature-pressure dynamics. They flow from high pressure or low temperature area to low pressure or high temperature area. In summers, the Asian landmass gets heated due to northward movement of the sun. Hence, the Indian subcontinent witnesses summer monsoons due to the change in pressure conditions in the subtropical landmass of Asia due to increase in temperature.

The south-west monsoon winds, after arriving at the southern tip of the Indian peninsula, get divided into two branches - (1) Arabian Sea branch, and (2) Bay of Bengal branch. The Arabian Sea branch blows in south-westerly direction. But the Bay of Bengal branch gets deflected towards north-west due to three factors - (1) Arakan Hills of Myanmar, (2) Himalayas of the North India and (3) Thermal low pressure over North India. This leads to change in the direction of this branch from south-westerly to south-easterly direction.

All the given factors influence the nature and mechanism of monsoons.

The south-west monsoon winds, after arriving at the southern tip of the Indian peninsula, get divided into two branches - (1) Arabian Sea branch, and (2) Bay of Bengal branch. Both these branches of winds blow towards the interior parts of land. But the farther they move from the sea, the lesser becomes their rain bringing capacity. The Arabian Sea branch gets almost water deficient reaching the foothills of the Shiwaliks. Getting reinforced by the Bay of Bengal Branch, the Arabian Sea branch of monsoon winds brings some showers to the Western Himalayas in the summer season. It should be kept in mind that the Western Himalayas receive rainfall in winter season from the Western disturbances.

The jet stream is a river of wind that blows horizontally through the upper layers of the troposphere, generally from West to East at an altitude of 20,000 - 50,000 feet (6,100 - 9,144 metres) or about 7 miles (11 kilometres) up. There are different jet streams and in respect of the climate and monsoons of India, it is the Subtropical Jet Stream (STJ) and the countering easterly jet that are most important. As the summertime approaches, there is increased solar heating of the Indian subcontinent. This has a tendency to form a cyclonic monsoon cell situated between the Indian Ocean and southern Asia. This cell is blocked by the STJ which tends to blow to the South of the Himalayas; as long as the STJ is in this position, the development of summer monsoons is inhibited. During the summer months, the STJ deflects northwards and crosses over the Himalayan Range. The altitude of the mountains initially disrupts the jet, but once it has cleared the summits, it is able to reform over central Asia. With the STJ out of the way, the sub-continental monsoon cell develops very quickly indeed, often in a matter of a few days. In winters, an easterly jet stream, called the tropical easterly jet stream blows over peninsular India, approximately over 14°N during the summer months. Thus, it affects most part of Indian climate throughout the year.

Characteristics of evening dust storms that blow in north-western India during May:

1. They are non-permanent or temporary in nature and blow in the heart of the low pressure trough in the north-west direction.
2. They are dry day winds
3. They may prove fatal
4. These storms along with the oppressive heat of the season add challenges to human life.

Statement 1 is incorrect: Monsoons are seasonal winds that change their direction with respect to the temperature-pressure dynamics. They flow from high pressure or low temperature area to low pressure or high temperature area. During cold weather season, a feeble high temperature area is developed in the northern part of India and strong winds with a high velocity of 30-50 km per hour begin to blow outwards. Statement 2 is perfectly correct: Before reaching the north-western part of the country, the Western disturbances that originate over the Mediterranean Sea travel eastwards across West Asia, Iran-Afghanistan and Pakistan, with their moisture content augmented from Caspian Sea in north and Persian Gulf in south.

Statement 1 is correct: Pattern of winds is always a manifestation of pressure-temperature dynamics. The pattern of planetary winds is modified by the centres of high pressure and low pressure. Statement 2 is incorrect: Winds blow in anticlockwise direction around a low pressure centre (i.e. cyclone) and in clockwise direction around a high pressure centre (i.e. anti-cyclone). Statement 3 is incorrect: Wind speed is not the criterion for classification of monsoon winds. Monsoon winds are rather, characterised by seasonal reversal of wind direction.

Statement 1 is correct: During December to February, light winds of low velocity blow over the Ganga-Brahmaputra Delta in the northerly direction. Statement 2 is incorrect: The very light rainfall brought by Western disturbances is highly beneficial for Rabi crops, especially wheat. Statement 3 is correct: Incursion of the pre-monsoon showers and early advance of the monsoons further north is checked by a belt of relatively high air pressure lying over the Deccan Plateau.

All the statements, except statement 3, are correct. Coromandel Coast is the coastal area of Tamil Nadu and southern Andhra. This area does not experience summer rain due to parallel direction of the rain bearing winds. Instead, this region gets rain in winter season from the north-east jet streams.

The Arabian Sea branch reaches Mumbai on approximately the 10th of June.

The eastern coastline of India is the most vulnerable to cyclonic storms.The western coastline of India is less vulnerable to cyclonic storms, both in terms of intensity and frequency of cyclones.

The factors related to location and relief features, which determine the climate of India, are -

1. Latitudinal extent (not longitudinal extent): The Tropic of Cancer passes through the central part of India in east-west direction. 
2. Distribution of land and water: India is flanked by the Indian Ocean on three sides in the south and girdled by a high and continuous mountain-wall in the north. 
3. Distance from the sea: With a long coastline, large coastal areas have an equable climate. Areas in the interior of India are far away from the moderating influence of the sea. 
4. Altitude: Temperature decreases with height. Due to thin air, places in the mountains are cooler than places on the plains. For example, Agra and Darjeeling are located on the same latitude, but temperature of January in Agra is 16°C whereas it is only 4°C in Darjeeling. 

Great Indian Desert sometimes receives poor and erratic rainfall during the advancing monsoon season. But Lahul-Spiti region does not experience ANY rainfall in advancing monsoon season due to its extreme continentality (location is too interior for the moisture-laden winds to encroach) and Coromandel coast also does not receive ANY rainfall. It lies on the leeward side (rain-shadow area) of the Western Ghats because of which it does not receive any rainfall in summer due to the south-west monsoon.

The season of retreating monsoon is marked by clear skies and rise in temperature. The land is still moist. Owing to the conditions of high temperature and humidity, the weather becomes rather oppressive. This is commonly known as the 'October heat'. (Hence, option 3 is correct). In the second half of October, the mercury begins to fall rapidly, particularly in northern India. The weather in the retreating monsoon is dry in North India but it is associated with rain in the eastern part of the Peninsula. Here, October and November are the rainiest months of the year. The widespread rain in this season is associated with the passage of cyclonic depressions which originate over the Andaman Sea and manage to cross the eastern coast of the southern Peninsula. These tropical cyclones are very destructive. The thickly populated deltas of the Godavari, Krishna and Kaveri are their preferred targets. (Hence, option 1 is correct).