Monsoon Rhythms: Rainfall in India’s Patterns

The distribution of rainfall in India is influenced by various factors, including the monsoon winds, topography, and proximity to water bodies.

India primarily experiences two major monsoon seasons: the southwest monsoon and the northeast monsoon.

Broad overview of the rainfall in India: Zones, Depths, and Himalayan Snowfall

• The average annual rainfall in India is about 125 cm, but it has great spatial variations (Refer Figure ).
• High Rainfall Zones (over 200 cm):  These regions include the west coast, Western Ghats, and the sub-Himalayan areas in the northeast, especially parts of the Khasi and Jaintia hills, which receive more than 1,000 cm. 
  • The Brahmaputra valley and adjoining hills get slightly less, under 200 cm.
• Medium Rainfall Zones (100-200 cm): Areas receiving between encompass southern Gujarat, east Tamil Nadu, northeastern Peninsula, and
  • Areas covering Odisha, Jharkhand, Bihar, eastern Madhya Pradesh, northern Ganga plain, and parts of the northeast.
• Low Rainfall Zones (50-100 cm): Regions like western Uttar Pradesh, Delhi, Haryana, Punjab, Jammu and Kashmir, eastern Rajasthan, Gujarat, and the Deccan Plateau.
• Inadequate Rainfall Zones: These regions receive less than 50 cm of rainfall in India.
  • Certain parts of the Peninsula, notably in Andhra Pradesh, Karnataka, Maharashtra, Ladakh, and most of western Rajasthan.
• Snowfall: This phenomenon is limited to the Himalayan region.

India: Annual Rainfall

Variability of Rainfall in India: Patterns Across Regions

• A characteristic feature of rainfall in India is its variability. The variability of rainfall in India is computed with the help of the following formula:

• Areas with less than 25% variability: It  includes the western coasts, Western Ghats, north-eastern Peninsula, eastern Ganga plains, north-eastern India, Uttarakhand, Himachal Pradesh, and southwestern Jammu and Kashmir. 
  • These regions typically receive more than 100 cm of annual rainfall in India.
• A Variability of Over 50%: It includes regions like western Rajasthan, northern Jammu and Kashmir, and the interior Deccan plateau, 
  • These regions  receive less than 50 cm of rainfall in India annually.

 A Variability Ranging from 25% to 50%: The remaining parts of India, receiving between 50-100 cm of rainfall in India, (Refer to Figure).

India: Variability of Annual Rainfall

Climatic Regions of India: Diverse Zones Shaping India’s Weather

• Koeppen’s classification: It is based upon specific letter symbols such as 
  • ‘S’ for semi-arid regions and ‘W’ for arid regions. 
  • Further sub-divisions were marked by additional lowercase letters like ‘f’ for sufficient precipitation or ‘m’ for rainforests with a dry monsoon season. 

India : Climatic Regions According to Koppen’s Scheme

• He delineated five primary climatic types:
  • Tropical climates: Mean monthly temperatures are consistently above 18°C throughout the year.
  • Dry climates: 
    • Precipitation is notably low relative to temperature. 
    • These are further categorised as semi-arid (S) or arid (W).
  • Warm temperate climates: The coldest month has a mean temperature ranging between 18°C and -3°C.
  • Cool temperate climates: The warmest month averages above 10°C, while the coldest month falls below -3°C.
  • Ice climates: The warmest month’s mean temperature remains below 10°C.
• As per Koeppen’s scheme, India comprises eight distinct climatic regions (Refer to Table and Figure).

Table: Climatic Regions of India According to Koeppen’s Scheme

Monsoons and Economic Life in India: India’s Agricultural Tapestry

• Agriculture’s Dependence on Monsoon: The agricultural cycle in India heavily depends on the monsoon, as the majority of the population relies on farming. 
  • The majority of this agriculture is centered around the patterns of the southwest monsoon.
• Temperature and Crop Growth: Barring the Himalayas, India’s temperature is conducive to year-round crop cultivation.
• Diversity in Crops: India’s varied monsoon climates allow for the cultivation of a diverse range of crops.
• Challenges from Rainfall Variability: Inconsistent rainfall in India can lead to droughts or floods, affecting regions annually.
• Prosperity Tied to Rainfall: Timely and adequate rainfall in India is crucial for agriculture, especially in areas without developed irrigation. 
  • Any failure in monsoon patterns can severely impact agricultural output.
• Soil Erosion Issues: The sudden onset of the monsoon can cause widespread soil erosion.
• Winter Rainfall in India’s Benefits: In northern India, rainfall in India during winter, brought by temperate cyclones, aids the growth of rabi crops.
• Lifestyle: The regional climatic variations influence the diverse food habits, clothing preferences, and housing styles across India.

Global warming: Causes and Consequences of Global Change

• Meaning: It refers to the long-term warming of the planet’s overall temperature. 
• The Greenhouse Effect: An increase in gases such as carbon dioxide, methane, chlorofluorocarbons, and nitrous oxide termed “greenhouse gases” intensifies the greenhouse effect. 
  • These gases absorb long-wave radiation more effectively than carbon dioxide, leading to a rise in Earth’s temperature.

Consequences  of Global Warming: Melting Ice, Rising Temperatures

• Melting Polar Regions: Due to global warming, polar ice caps and mountain glaciers are melting, causing ocean levels to rise.
• Projected Temperature Rise: Over the past 150 years, Earth’s surface temperature has increased. 
  • Predictions indicate a further 2°C rise by 2100.
• Sea Level Concerns: It’s estimated that sea levels will rise by 48 cm by the end of the 21st century, which would lead to more frequent flooding events.

Conclusion

• India’s weather is a mix of complex patterns primarily influenced by the monsoons. 
• The oscillation between the dry north-easterly winds and moisture-rich south-westerly winds produces the subcontinent’s different climatic zones, however, the Himalayas and the oceans also play important roles in regulating temperatures. 
• India’s climate is an excellent example of both unity and diversity, with severe temperatures in places like Rajasthan and Ladakh and a variety of precipitation patterns from Meghalaya to Tamil Nadu. 
• This climatic variation has a profound impact on many facets of life, including agriculture and cultural practices, and is a crucial component of the identity of the country.

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