Seasonality and Distribution of Rainfall in India – UPSC Indian Geography Notes

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India, with its diverse geography and varied climate patterns, experiences a rich tapestry of seasonal changes, prominently manifested in the distribution of rainfall across the subcontinent. Seasonality and the distribution of rainfall play a pivotal role in shaping India’s agricultural, ecological, and socio-economic landscapes. From the torrential monsoon rains that inundate the southwest coast to the arid regions of the northwest, the intricate dance of precipitation patterns influences cropping patterns, water resource management, and the livelihoods of millions. Understanding the nuances of this seasonal rhythm is essential for comprehending India’s ecological balance and its resilience to climatic variations. This essay explores the dynamic interplay of seasonal shifts and rainfall distribution, unraveling the complex tapestry of India’s meteorological mosaic.

The significant diversity in climatic patterns is influenced by the following factors:

1. Location
2. Altitude
3. Distance from the sea
4. General Topography

• Location
  • In India, the Southern states of Tamil Nadu and Kerala receive substantial annual rainfall, while the Northern regions encounter elevated precipitation levels.
• Altitude
  • The precipitation is notably elevated in regions with higher elevations in the country. This is attributed to the colder weather and atmospheric conditions, which are less capable of retaining condensation, leading to more frequent rainfall or snowfall. Conversely, lower elevations experience higher humidity, allowing moisture to linger in the atmosphere, resulting in comparatively lower rainfall.
• Distance from the Sea
  • The coastal regions of the country exhibit a higher annual rainfall in contrast to the plateau areas. Rainfall diminishes progressively as one moves farther away from the seashore.
• General Topography
  • Mountains play a crucial role in determining rainfall patterns in topographic regions. Serving as barriers, they capture clouds in specific areas, making hilly and mountainous regions of the country susceptible to substantial rainfall.

SEASONALITY OF RAINFALL

The seasonality of rainfall in India is primarily influenced by the monsoon winds, which are a dominant climatic feature. India experiences a distinct wet and dry season, with the monsoon playing a crucial role in determining the distribution and timing of rainfall across the country. 

The seasonal pattern of rainfall can be broadly categorised into three main seasons: the Southwest Monsoon, the Northeast Monsoon, and the Pre-Monsoon or Summer Monsoon.

Southwest Monsoon (June to September):

• The Southwest Monsoon is the most significant contributor to India’s annual rainfall, bringing about 70-90% of the total precipitation.
• It typically starts in early June, with the onset marked by the arrival of monsoon winds over the southern tip of the Indian subcontinent. These winds gradually advance northward, covering the entire country by July.
• The southwest monsoon brings heavy rainfall to the Western Ghats, the eastern slopes of the Western Ghats, and the northeastern regions of the country.
• The west coast and the windward side of the Western Ghats receive particularly intense rainfall due to orographic lifting, where moist air is lifted by the mountains, leading to cooling and condensation.

Northeast Monsoon (October to December):

• The Northeast Monsoon, also known as the retreating monsoon, occurs as the monsoon winds reverse their direction and withdraw from the Indian subcontinent.
• This season brings rainfall to the southeastern parts of India, including Tamil Nadu, coastal Andhra Pradesh, and parts of Karnataka.
• The northeast monsoon is generally less intense than the southwest monsoon but is crucial for regions that receive minimal rainfall during the southwest monsoon.

Pre-Monsoon or Summer Monsoon (March to May):

• The pre-monsoon season precedes the onset of the southwest monsoon and is characterized by rising temperatures.
• During this period, some parts of India experience pre-monsoon showers, especially in the form of localized thunderstorms, providing relief from the heat.
• The western Himalayan region also receives rainfall during this season.

The variation in rainfall seasonality is also influenced by factors such as the El Niño and La Niña phenomena, which can lead to deviations from the normal monsoon patterns, impacting the timing and distribution of rainfall.

It’s important to note that the diverse topography of India contributes to regional variations in rainfall, and different parts of the country may experience distinct seasonal patterns based on their geographical features. 

Overall, the monsoon system plays a critical role in shaping India’s climate and agriculture, making the understanding of rainfall seasonality crucial for various aspects of life in the country.

Rainfall Distribution in India

Annually, the Indian subcontinent receives an average rainfall of 125 cm (890 mm). The country’s extensively varied topography contributes to significant variations in annual rainfall distribution. 

This diversity leads to the classification of the country into five major regions based on the amount of rainfall they receive each year. These regions are categorized as follows:

1. Regions with Extreme Precipitation
2. Regions with Heavy Precipitation
3. Regions with Moderate Precipitation
4. Regions with Scanty Precipitation
5. Desert and Semi-arid Regions

Regions with Extreme Precipitation

• The North-eastern regions of the Indian subcontinent and the lower segments of the Western Ghats experience an annual rainfall that reaches as high as 400 cm. 
• Specifically, the eastern areas of Assam, Meghalaya, Arunachal Pradesh, and the mountainous regions of the Western Ghats are characterized by tropical rainforests, resulting in the highest precipitation levels in the country.
• Notably, the village of Mawsynram, situated in the hilly regions of the North-eastern state of Meghalaya, stands out as the area with the highest precipitation in the country. 
• With an average annual precipitation of 11,861 millimeters (467 in), Mawsynram is recognized not only for having the highest recorded precipitation in the entire Asian continent but also possibly on Earth. 
• Positioned at an elevation of approximately 1,401 meters (4,596 ft), it holds the distinction of being the wettest place known to mankind.
• Cherrapunji, another village located in the state of Meghalaya, is also renowned for its exceptionally high average annual precipitation levels, measuring about 11,430 mm (450 in).

Regions with Heavy Precipitation

• The areas of the country characterized by an annual rainfall ranging from approximately 200 to 300 cm are designated as Heavy Precipitation Regions. 
• This climatic zone encompasses various parts of Eastern India, including states such as West Bengal, Tripura, Nagaland, Manipur, Orissa, and Bihar.
• These regions are notable for hosting extensive tropical rainforests where rainfall occurs consistently throughout the year. 
• Additionally, a segment of the Himalayan Mountain Belt falls within this zone, contributing to the elevated precipitation levels experienced in these areas.

Regions with Moderate Precipitation

• Areas in the country receiving an annual rainfall ranging from approximately 100 to 200 cm fall into the category of Moderate Precipitation Regions. 
• This climatic zone includes the eastern segments of the Western Ghats and states such as Madhya Pradesh, Andhra Pradesh, Bihar, West Bengal, and Orissa.
• Characterized by a semi-arid climate, this type of region experiences a moderate level of rainfall throughout the year.

Regions with Scanty Precipitation

• Areas in the country receiving an annual rainfall ranging from approximately 50 to 100 cm are classified as Scanty Precipitation Regions. 
• This climatic zone encompasses various parts of Haryana, Punjab, Gujarat, Madhya Pradesh, Maharashtra, Andhra Pradesh, Karnataka, and Tamil Nadu.

Desert and Semi-arid Regions

• Areas in the country receiving an annual rainfall of less than 50 cm are designated as the Desert and Semi-arid Regions. 
• These regions are predominantly found in the states of Rajasthan and Gujarat, characterized as hot deserts. 
• Additionally, certain parts of the state of Jammu & Kashmir are also encompassed within this classification, recognized as cold deserts.

FAQs About India’s Climatic Diversity and Rainfall Patterns:

1. Why is India considered one of the most climatically diverse countries globally?

India’s diverse climatic conditions are primarily due to its varied topography, encompassing mountains, plateaus, plains, and coastlines. This geographical diversity, combined with factors like location, altitude, distance from the sea, and general topography, contributes to the wide range of weather conditions experienced across the nation.

2. How does location affect rainfall distribution in India?

In India, the Southern states of Tamil Nadu and Kerala receive substantial annual rainfall, while the Northern regions encounter elevated precipitation levels. This variation in location is a key factor influencing the distribution of rainfall across the country.

3. What role does altitude play in India’s precipitation patterns?

Regions with higher elevations experience notably elevated precipitation due to colder weather and atmospheric conditions, leading to more frequent rainfall or snowfall. In contrast, lower elevations with higher humidity have comparatively lower rainfall.

4. How does proximity to the sea influence rainfall in India?

Coastal regions of India exhibit higher annual rainfall compared to plateau areas. Rainfall gradually decreases as one moves farther away from the seashore. The sea’s moderating effect on temperature contributes to the variation in precipitation patterns.

5. How do mountains impact rainfall distribution in India?

Mountains act as barriers, trapping clouds in specific areas and influencing rainfall patterns. Hilly and mountainous regions, such as the Western Ghats, are more susceptible to substantial rainfall due to orographic lifting, where moist air is lifted by the mountains, leading to cooling and condensation.

6. What are the main seasons influencing rainfall in India?

India experiences three main seasons: the Southwest Monsoon (June to September), the Northeast Monsoon (October to December), and the Pre-Monsoon or Summer Monsoon (March to May). These seasons are characterized by distinct rainfall patterns influenced by the monsoon winds.

7. How significant is the Southwest Monsoon in India’s annual rainfall?

The Southwest Monsoon is the most significant contributor, bringing about 70-90% of India’s annual precipitation. It starts in early June, gradually covering the entire country by July. Regions like the Western Ghats and northeastern areas receive heavy rainfall during this season.

8. Which regions in India experience extreme precipitation?

The North-eastern regions and the lower Western Ghats experience extreme precipitation, with annual rainfall reaching as high as 400 cm. Villages like Mawsynram in Meghalaya hold records for the highest precipitation in Asia and possibly on Earth.

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