Climate (India Basic)

Climatic Controls

Climatic controls are factors that influence the climate of a region. India's diverse climate is shaped by several such controls:

1. Latitude: India lies in the Northern Hemisphere. The Tropic of Cancer passes through the central part of the country, dividing it into two distinct climatic zones: a tropical zone in the south and a subtropical zone in the north.

2. Altitude: The elevation of a region significantly affects its temperature. Higher altitudes generally experience lower temperatures. For example, the Himalayas are much colder than the plains.

3. Pressure and Winds: The distribution of atmospheric pressure and the resultant wind patterns are crucial in determining rainfall and temperature. India experiences seasonal winds (monsoons) that play a dominant role in its climate.

4. Distance from the Sea: Coastal areas tend to have a more moderate climate (equable climate) with less extreme temperature variations, while inland areas experience continental climates with greater temperature fluctuations.

5. Relief Features: The topography of the land, including mountains, plateaus, and plains, influences temperature, rainfall, and wind. For instance, the Himalayas act as a barrier, preventing cold winds from Central Asia from entering the subcontinent and also influence monsoon patterns.

6. Ocean Currents: While not as direct an influence as in some other regions, ocean currents can indirectly affect coastal climates.

7. Upper Air Circulation: The development of the westerly jet stream during winter and the easterly jet stream associated with the Indian monsoon are significant factors.

Factors Affecting India’s Climate

India's climate is a complex interplay of various geographical and atmospheric factors:

Latitude

India straddles the Tropic of Cancer (23.5° N). This means that the southern part of India, south of the Tropic of Cancer, experiences a tropical climate, characterized by high temperatures and minimal seasonal variation. North of the Tropic of Cancer, India falls into the subtropical zone, experiencing more distinct seasons with greater temperature variations between summer and winter.

Altitude

The Himalayas in the north significantly influence India's climate. The high altitude of these mountains causes temperatures to decrease with increasing elevation. Thus, while the northern plains can be scorching hot in summer, places like Shimla or Darjeeling at higher altitudes remain cool.

The altitude also affects precipitation patterns, with windward slopes receiving more rainfall than leeward slopes.

Pressure And Winds

This is one of the most crucial factors determining India's climate, primarily through the phenomenon of the Indian monsoon.

Underlying Principles:

• Pressure Differences: Land heats up and cools down faster than water. This creates pressure differences between continents and oceans.
• Winds: Winds blow from areas of high pressure to areas of low pressure.

Seasonal Variations in Pressure:

• Winter: High-pressure conditions develop over the northwestern parts of the Indian subcontinent, with cold, dry winds blowing from the land to the oceans.
• Summer: A prolonged period of intense heat leads to the formation of a low-pressure zone over the northern and northwestern parts of India. This draws in moisture-laden winds from the Indian Ocean.

The Indian Monsoon: The monsoon is a seasonal reversal of wind direction. The southwest monsoon winds, originating from the Indian Ocean, bring abundant rainfall to most parts of India during summer. Conversely, the northeast monsoon winds, originating from land, bring little rainfall to most of the country.

Jet Streams: The influence of upper air circulation, particularly the westerly jet stream in winter and the easterly tropical jet stream during the monsoon season, also plays a significant role in shaping India's weather patterns.

The Indian Monsoon

The Indian monsoon is a vital climatic phenomenon that dictates the weather patterns and agricultural cycle of the subcontinent. It is characterized by seasonal winds that reverse their direction annually, bringing either abundant rainfall or dry conditions.

The Onset Of The Monsoon And Withdrawal

Onset:

• The Indian monsoon typically sets in around the first week of June in the southernmost part of India (Kerala).
• It advances progressively northwards, covering the entire country by mid-July.
• The onset is often heralded by a sudden increase in rainfall, which is known as the 'break' or 'burst' of the monsoon. This is accompanied by strong winds and thunderstorms.
• The arrival of the monsoon is influenced by the differential heating of land and sea, leading to the formation of a low-pressure area over northwestern India.
• The easterly jet stream plays a crucial role in the onset and establishment of the monsoon.

Withdrawal:

• The withdrawal of the monsoon begins in northwestern India around the first week of September.
• It recedes gradually from most of the country by mid-October.
• The withdrawal is generally more gradual than the onset.
• The retreating monsoon leaves behind a clear sky and pleasant weather conditions.

Variability: The timing and intensity of the monsoon can vary from year to year, leading to droughts or floods. Factors like El Niño and La Niña can influence the monsoon's performance.

The Seasons

India experiences distinct seasons, primarily dictated by the monsoon patterns. These can be broadly classified into four main seasons:

The Cold Weather Season (Winter)

Period: December to February.

Characteristics:

• Temperature: Clear skies, dry weather, and low temperatures. Frost is common in the north. Day temperatures are pleasant, but nights are cold.
• Pressure and Winds: High-pressure systems prevail over northern India, with winds blowing from the land to the seas. These winds are dry as they originate from the landmass.
• Rainfall: Little to no rainfall in most parts of the country. However, light rainfall may occur in the plains due to the passage of western disturbances (cyclonic disturbances originating from the Mediterranean region). The northern slopes of the Himalayas receive snowfall.
• Northeast Monsoon: During this season, the northeast monsoon winds blow from land to sea, but some moisture is picked up from the Bay of Bengal, causing light rainfall in Tamil Nadu and adjoining areas of Andhra Pradesh.

The Hot Weather Season (Summer)

Period: March to May.

Characteristics:

• Temperature: Increasing temperatures across the country, with the hottest months being April and May. Peninsular India experiences moderate temperatures due to the moderating influence of the oceans.
• Pressure and Winds: A prolonged period of intense heat leads to the formation of a low-pressure area over northwestern India. This causes hot, dry winds to blow locally, known as 'Loo'.
• Rainfall: Generally dry, but some pre-monsoon showers, often called 'mango showers', are experienced in some parts of southern India (e.g., Kerala and Karnataka), which are beneficial for mangoes and cashews. Dust storms are common in northern India.

Advancing Monsoon (The Rainy Season)

Period: June to September.

Characteristics:

• Onset: This season is dominated by the southwest monsoon winds, which bring abundant rainfall to most parts of India. The monsoon typically starts in Kerala in early June and advances northwards.
• Rainfall: Heavy rainfall occurs across most of the country, with variations in intensity. The windward side of the Western Ghats and the northeastern states receive very heavy rainfall.
• Temperature: Temperatures tend to fall with the onset of the monsoon due to cloud cover and rain.
• Variability: The monsoon is characterized by 'breaks' (periods of dry spells) and 'bursts' (periods of heavy rainfall).

Retreating/Post Monsoons (The Transition Season)

Period: October to November.

Characteristics:

• Withdrawal: The monsoon starts withdrawing from northwestern India in early September and gradually recedes from the rest of the country by mid-October.
• Sky and Temperature: The sky becomes clear, and temperatures begin to rise again, leading to a season of transition.
• Northeast Monsoon: During this period, the retreating monsoon winds pick up moisture from the Bay of Bengal and cause rainfall in the southeastern coastal areas of India, particularly Tamil Nadu, southern Andhra Pradesh, and Kerala. This is also known as the 'northeast monsoon' or 'winter monsoon'.
• Clear Skies: The transition leads to clear skies and the formation of conditions conducive to the onset of the cold weather season.

Distribution Of Rainfall

The distribution of rainfall in India is highly uneven, influenced by the climatic controls mentioned earlier, particularly the monsoon system and relief features. This unevenness leads to significant regional variations:

1. Areas of Heavy Rainfall:

• The western coasts and the northeastern parts of the country receive more than 400 cm of rainfall annually.
• These include the windward side of the Western Ghats, the Sahyadri ranges, and the northeastern states (Meghalaya, Assam, Arunachal Pradesh). Mawsynram in Meghalaya receives the highest average rainfall in the world.

2. Areas of Moderate Rainfall:

• These regions receive 100 cm to 200 cm of rainfall annually.
• This includes the Ganga valley, Odisha, Bihar, eastern Madhya Pradesh, northern Andhra Pradesh, and the western coastal plains.

3. Areas of Low Rainfall:

• Regions receiving 50 cm to 100 cm of rainfall annually.
• This includes the upper Ganga valley, Punjab, Haryana, eastern Rajasthan, and parts of the Deccan Plateau.

4. Areas of Very Low Rainfall (Arid and Semi-Arid Regions):

• These regions receive less than 50 cm of rainfall annually.
• This primarily includes Rajasthan (especially the western parts like Jaisalmer and Bikaner), Gujarat, and the rain shadow areas of the Western Ghats.

Factors Influencing Distribution:

• Monsoon Winds: The direction and intensity of monsoon winds.
• Relief: Mountain ranges like the Western Ghats and the Himalayas create rain shadow areas on their leeward sides.
• Distance from the Sea: Inland areas generally receive less rainfall than coastal areas.
• Tropical Cyclones: Coastal areas are also affected by tropical cyclones, which bring heavy rainfall.

Monsoon As A Unifying Bond

The Indian monsoon, despite its variability and regional differences in intensity, acts as a powerful unifying force that binds the diverse country together in several ways:

1. Agricultural Backbone: Agriculture, which is practiced by a majority of the Indian population, is critically dependent on the monsoon rains. The timely arrival and adequate distribution of monsoon rains determine the agricultural output, which in turn impacts the economy and food security of the nation.

2. Shared Experience: The entire country experiences the onset and withdrawal of the monsoon, albeit with variations. This shared experience creates a common rhythm to life, influencing festivals, economic activities, and daily routines across different regions.

3. Cultural Significance: The monsoon is deeply ingrained in Indian culture, art, literature, and traditions. Numerous festivals are celebrated to welcome the rains or express gratitude for them. The imagery of the monsoon is a recurring theme in poetry, music, and paintings.

4. Economic Interdependence: The success or failure of the monsoon has a cascading effect on the entire economy, from agriculture and food prices to industrial production and trade. This interconnectedness fosters a sense of shared destiny.

5. National Discourse: The performance of the monsoon is a constant topic of discussion and concern across the nation, from the highest policy levels to individual households. This shared focus highlights a common national interest.

6. National Integration: The shared dependence on and experience of the monsoon contribute to a sense of national identity and integration, bridging regional, linguistic, and cultural differences.