Distribution of Rainfall

Distribution of Rainfall – UPSC World Geography Notes

Precipitation varies widely across the globe, influenced by the distinct climatic conditions in different regions. Certain areas receive abundant Rainfall, whereas others experience minimal precipitation.

The Equator and adjacent tropical regions receive substantial rainfall, contributing to the world’s average annual precipitation of approximately 100 cm. This article aims to elucidate the Global Distribution of Rainfall, providing valuable insights for those preparing for the UPSC Civil Service exam in Geography.

Global Distribution of Rainfall – Concept

  • Global rainfall distribution is uneven, influenced by climatic conditions in different regions.
  • Some areas experience high rainfall, while others face scarce precipitation.
  • Tropical and equatorial regions, in particular, receive substantial rainfall.
  • The world’s average annual rainfall is approximately 100 cm.

Distribution

  • Rainfall across the Earth’s surface varies seasonally and annually.
  • Generally, rainfall decreases from the equator towards the poles.
  • Coastal areas receive more rainfall than continental interiors due to the water-rich nature of seas.
  • Eastern beaches between 35° and 40° N and S of the equator experience higher rainfall, decreasing westward.
  • Westerlies contribute to initial rainfall on western borders between 45° and 65° N and S, decreasing eastward.
  • Rainfall is higher on windward coastal plains and diminishes on leeward sides with parallel mountain ranges.
  • Principal precipitation regimes are categorized based on annual precipitation levels:
    • Equatorial belt, western slopes of cold temperate zone mountains, and coastal sections of monsoon land receive over 200 cm annually.
    • Interior continental areas receive 100 – 200 cm per annum, while coastal areas receive moderate rainfall.
    • Central parts of tropical land and eastern/interior parts of temperate lands receive 50 – 100 cm per annum.
    • Rain shadow zones in continental interiors and high latitudes receive less than 50 cm per annum.
  • Seasonal distribution of rainfall varies; equatorial belt and western parts of cool temperate regions exhibit even distribution throughout the year.

Rainfall in India

India, a vast country geographically, exhibits diverse climatic conditions across its regions, a diversity mirrored in its rainfall distribution. While some areas receive abundant rainfall, others face scarcity. The contrast between the highest and lowest recorded rainfall in India is approximately 1178 cm. This article will explore different zones of the country based on average annual rainfall, an essential topic in the Geography Syllabus for UPSC Prelims and Mains.

Rainfall Distribution in India

In India, precipitation exhibits irregular patterns throughout the year, characterized by a distinct rainy season typically from June to September. According to the Koppen climate classification, India can be categorized into seven climatic regions:

  1. Tropical semi-arid
  2. Sub-tropical arid desert
  3. Sub-tropical semi-arid
  4. Tropical rainforest
  5. Tropical Savannah
  6. Sub-tropical humid
  7. Alpine

The average annual rainfall in India is 118 cm, as per Meteorological Department data. The distribution of rainfall in India can be delineated as follows:

  1. Extreme Precipitation regions: The northeastern regions and the windward side of the Western Ghats experience exceptionally high annual rainfall, averaging around 400 cm. Areas such as Assam, Meghalaya, Arunachal Pradesh, and the hilly tracts of the Western Ghats host tropical rainforests. Mawsynram village in Meghalaya holds the record for the highest rainfall in India and the world.
  2. Heavy Precipitation regions: Regions receiving 200-300 cm of rainfall fall into this category, covering most of Eastern India. States like West Bengal, Tripura, Nagaland, Manipur, Odisha, and Bihar, along with sub-Himalayan areas, are part of this zone and feature tropical rainforests.
  3. Moderate Precipitation regions: Areas experiencing 100 to 200 cm of rainfall include parts of West Bengal, Bihar, Odisha, Madhya Pradesh, Andhra Pradesh, and the leeward side of the Western Ghats. Wet deciduous forests are prevalent in these regions.
  4. Scanty Precipitation regions: Areas with 50 to 100 cm of rainfall encompass parts of Maharashtra, Gujarat, Karnataka, Tamil Nadu, Andhra Pradesh, Madhya Pradesh, Punjab, Haryana, and Western Uttar Pradesh. Common vegetation in these areas includes tropical grasslands, savannah, and dry deciduous forests.
  5. Desert and Semi-desert Regions: Regions receiving below 50 cm of rainfall, including states like Rajasthan, Gujarat, and adjacent areas, are classified as desert or semi-desert. Some parts of Jammu & Kashmir, like the Ladakh plateau, are included as cold deserts. Vegetation in these areas comprises hardy species adapted to prolonged droughts, with some regions featuring Savannah vegetation. The lowest recorded rainfall in India is in Ruyli village, Rajasthan.

The distribution of rainfall in India is influenced by both the Thar Desert and the Himalayas. Additionally, temperature and pressure variations over the Indian Ocean, the Arabian Sea, the Bay of Bengal, and the southern part of the Pacific Ocean contribute significantly to the monsoon rains across the country.

For UPSC aspirants focusing on the IAS Geography syllabus, a deeper understanding of monsoon rains in India is essential. It holds substantial importance in comprehending the physical, economic, and human Geography of the nation. Consequently, UPSC question papers often feature inquiries related to rainfall, underlining its relevance for exam preparation.

Significance of Rainfall

  • Essential for the survival of plants and animals, rainfall plays a crucial role.
  • It serves as the primary source of fresh water on the earth’s surface.
  • Low rainfall can result in water scarcity, potentially leading to drought-like conditions.
  • As a significant component of the water cycle, rain deposits a substantial portion of the world’s freshwater.
  • Rain creates favorable conditions for diverse habitats and serves as a vital resource for hydroelectric power facilities and agricultural irrigation.
  • The presence of moisture in rain contributes to cooling the air in general.

Conclusion

The distribution of rainfall plays various significant roles, including its influence on the formation of specific climates. Additionally, its presence in the atmosphere contributes to direct evaporation, replenishing moisture and heat within cloud systems.

FAQs on the Distribution of Rainfall

Q. What is the general distribution of world rainfall?

Answer: The distribution of world rainfall varies widely across different regions due to factors such as latitude, topography, and proximity to large water bodies. Generally, equatorial regions receive higher rainfall compared to polar and desert regions.

Q. How is rainfall distributed across the world?

Answer: Rainfall is unevenly distributed across the world, with patterns influenced by atmospheric circulation, prevailing winds, and geographic features. Regions near the equator typically experience high rainfall, while arid regions, like deserts, receive minimal precipitation.

Q. Describe the distribution of rainfall in India.

Answer: The distribution of rainfall in India is diverse, influenced by the Indian Ocean, Himalayan mountains, and monsoon winds. The southwest monsoon, occurring from June to September, brings the majority of rainfall to the country, with the western coast and northeastern states receiving the highest amounts.

Q. Explain the distribution of rainfall in India.

Answer: The distribution of rainfall in India is characterized by a monsoonal pattern, influenced by the southwest and northeast monsoons. Coastal areas, such as the Western Ghats and northeastern states, experience heavy rainfall, while the northwestern and interior regions receive comparatively less precipitation.

Q. What is the annual distribution of rainfall in India?

Answer: The annual distribution of rainfall in India is uneven, with distinct wet and dry seasons. The southwest monsoon, which brings the majority of rainfall, occurs from June to September. The distribution varies across regions, with some areas experiencing a more balanced distribution throughout the year.

Q. Describe the general distribution of rainfall in India.

Answer: The general distribution of rainfall in India is influenced by the topography and the monsoonal winds. Coastal regions, such as the western coast and northeastern states, receive abundant rainfall, while the interior and northwestern regions experience comparatively lower precipitation. The Himalayan region also contributes significantly to regional rainfall.

Q. What is the world distribution of rainfall in the context of UPSC?

Answer: In the context of UPSC (Union Public Service Commission) exams, understanding the world distribution of rainfall involves knowledge of global climatic patterns, including factors such as the intertropical convergence zone, prevailing winds, and ocean currents. Aspirants need to be familiar with how these factors contribute to variations in rainfall across different regions of the world.

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