Climate of India

2: Climate of India: Seasons, Characteristics, Factors Affecting Monsoon and the Indian Monsoon

India's climate is diverse due to its vast geographical expanse, varied topography, and unique positioning within the tropics and subtropics. The country experiences different climatic conditions ranging from arid deserts to tropical rainforests, alpine tundra and humid coastal regions. The primary climatic control is the monsoon, which dominates much of the Indian subcontinent’s weather patterns.

Seasons of India and Their Characteristics

India experiences four distinct seasons based on the influence of the tropical and temperate weather systems. These are:

1. Winter (December to February)

Temperature: The winter months are characterized by cool and dry weather. Temperatures range from 10°C to 15°C in the north, while the southern regions remain warmer.

Characteristics:

a. a In the northern plains, temperatures can drop significantly, especially in Jammu and Kashmir, Himachal Pradesh, and Uttarakhand, where snowfall occurs.

b. b Frost and fog are common phenomena in northern India, especially during December and January. 

c  c The southern part of India remains relatively warm, with temperatures averaging around 20°C to 25°C.

d.   d Winds blow from the northeast during this season, known as the northeast monsoon, bringing dry weather to most parts of the country, but the southeastern coast (especially Tamil Nadu) receives some rainfall due to this monsoon.

2. Summer (March to May)

Temperature: Summer in India is marked by increasing temperatures, often exceeding 40°C in many parts of the country, especially in the northern plains and central India.

Characteristics:

• Northern India experiences scorching heat with temperatures soaring above 45°C in states like Rajasthan, Uttar Pradesh and Madhya Pradesh. The desert regions of Rajasthan (Thar Desert) experiences extreme heat.
• Dust storms, heatwaves, and hot winds called loo are common during this season, especially in the northern and western regions.
• The southern part of India, particularly coastal regions, remains relatively cooler due to the moderating effect of the seas, with temperatures around 30°C to 35°C.
• The pressure starts to decrease over the Indian landmass, setting the stage for the onset of the monsoon.

3. Monsoon (June to September)

Temperature: The onset of the monsoon brings down the high temperatures. Average temperatures range from 25°C to 30°C, depending on the region.

Characteristics:

• The Southwest Monsoon brings heavy rainfall to most parts of India, especially the western coast, the northeastern states, and the Himalayan foothills.
•  The Western Ghats receive some of the heaviest rainfall, especially in regions like Kerala, Karnataka, and Maharashtra.
• The eastern states, including West Bengal, Assam, and Meghalaya, also experience heavy rains.
• Some regions in northwestern India, such as Rajasthan, receive relatively less rainfall.
• Floods are a common occurrence in states like Assam, Bihar, and parts of Uttar Pradesh, while landslides occur in the hilly regions of the Western Ghats and the Himalayas.

e.      Rainfall during this season is crucial for agriculture, as the majority of Indian farming is dependent on the monsoon.

4. Post-Monsoon/Autumn (October to November)

Temperature: This transition season between monsoon and winter sees temperatures between 25°C and 30°C. The weather becomes cooler in the northern parts of India.

Characteristics:

a The retreating monsoon, also known as the northeast monsoon, brings rain to the southeastern parts of the country, particularly Tamil Nadu and Andhra Pradesh.

b The rest of the country begins to experience clear skies and declining humidity levels.

c.  c In southern India, the northeastern monsoon causes short bursts of heavy rainfall in coastal regions like Chennai.

d. d Temperatures drop gradually as the season progresses, marking the onset of winter in northern India.

Factors Affecting the Indian Monsoon

The Indian monsoon is influenced by a complex set of global and regional factors that determine the timing, intensity, and distribution of rainfall across the subcontinent. Some of the key factors affecting the monsoon include:

1. Differential Heating and Cooling

India's landmass heats up faster than the surrounding oceans during the summer. This leads to the development of a low-pressure area over the northern plains, while a high-pressure area forms over the Indian Ocean. This pressure difference pulls moisture-laden winds from the ocean towards the land, leading to the monsoon rains.

2. The Inter-Tropical Convergence Zone (ITCZ)

The ITCZ is a zone of low pressure near the equator where the trade winds from the northern and southern hemispheres converge. During summer, the ITCZ shifts northwards over India, bringing with it the moist monsoon winds from the southwest.

3. The Tibetan Plateau

The Tibetan Plateau plays a crucial role in monsoon circulation. In summer, the plateau heats up significantly, creating a strong thermal low-pressure area that helps draw in monsoon winds from the Indian Ocean. The height of the plateau also influences the movement of air masses and the intensity of monsoon rains.

4. El Niño and La Niña

El Niño and La Niña events in the Pacific Ocean significantly influence the Indian monsoon.

a.  El Niño is associated with warming of the Pacific Ocean's surface waters and is often linked to weaker monsoon rains and drought conditions in India.

b.  La Niña, on the other hand, involves the cooling of surface waters and is generally linked to stronger monsoons with above-average rainfall.

5. Indian Ocean Dipole (IOD)

The Indian Ocean Dipole refers to the difference in sea surface temperatures between the western and eastern Indian Ocean. A positive IOD (warmer waters in the west and cooler in the east) strengthens the monsoon, while a negative IOD weakens it.

6. Jet Streams

The position and movement of the subtropical westerly jet stream and the tropical easterly jet stream also impact the monsoon. The westerly jet stream over the Indian subcontinent shifts northward during the summer, facilitating the inflow of the monsoon winds. The tropical easterly jet, which develops in response to the heating of the Tibetan Plateau, also aids in the monsoon onset.

7. The Role of High-Pressure Systems

The presence of a high-pressure system over the southern Indian Ocean influences the direction and strength of the monsoon winds. The location and intensity of the Mascarene High, a subtropical high-pressure system, play a crucial role in determining the southwest monsoon winds’ strength.

The Indian Monsoon

India experiences two distinct monsoon patterns: the Southwest Monsoon and the Northeast Monsoon.

Southwest Monsoon (June to September)

a.     Onset: The southwest monsoon typically arrives in Kerala in early June, marking the onset of the rainy season. The monsoon then spreads northward and covers the entire country by mid-July.

b.   Mechanism: The southwest monsoon is driven by the low-pressure system that develops over the northern plains of India due to intense summer heating. Moist winds from the Indian Ocean are pulled towards the Indian landmass, where they rise and condense, leading to widespread rainfall.

c.   Regions Affected:

Ø The western coast of India (including Kerala, Karnataka, and Maharashtra) receives heavy rainfall due to the Western Ghats' orographic effect.

Ø The northeastern states (including Assam and Meghalaya) also receive significant rainfall.

Ø Central and northern India, including the Indo-Gangetic plains, experience moderate to heavy rains.   

Si Significance: The southwest monsoon is crucial for India's agriculture, which is largely rain-fed. Crops like rice, wheat, sugarcane and pulses rely heavily on monsoon rains.

Northeast Monsoon (October to December)

a.     Onset: After the southwest monsoon retreats in September, the northeast monsoon winds begin to blow from the northeast, bringing rains to southeastern parts of India, particularly Tamil Nadu and southern Andhra Pradesh.

b.  Mechanism: The northeast monsoon is caused by the reversal of wind patterns. The northeast winds pick up moisture from the Bay of Bengal and bring rain to southeastern coastal regions.

c.   Regions Affected:

Ø Tamil Nadu, which receives around 50% of its annual rainfall from the northeast monsoon.

Ø Coastal areas of Andhra Pradesh, Karnataka, and Kerala also receive rainfall during this period.

Climate of India

India’s climate is shaped primarily by the monsoons, which govern the weather patterns and significantly influence agriculture, water resources and overall economic activities. The monsoons' timing, intensity and distribution are crucial for India's agriculture and food security. Understanding the complex factors influencing the Indian monsoon is key to predicting and managing the impacts of monsoons, especially in light of climate change and increasing unpredictability in weather patterns. 

Keyword; Indian climate, Seasons, Characteristics, Factors, Indian Monsoon, Region