Roadmap for Answer Writing

Introduction

• Begin by introducing the significance of precipitation in India, noting that it constitutes 80% of the annual rainfall during the monsoon season.
• Mention the extreme spatial variation in precipitation from over 400 cm in some northeastern regions to less than 10 cm in the arid northwest (e.g., Rajasthan).

Spatial Variations in Precipitation

• Monsoon Influence:
  • Explain how the arrival and intensity of the monsoon affect precipitation distribution across the country.
  • Provide examples of regions like the Western Ghats, northeast India, and the western coast, which experience significant rainfall due to the southwest monsoon and the orographic effect.
• Rain Shadow Effect:
  • Highlight areas that receive low rainfall due to the rain shadow created by mountain ranges, such as parts of Rajasthan, the Deccan Plateau, and parts of the western coastal region.
  • Mention how the western Ghats play a role in blocking rainfall to the leeward side.
• Northeastern States:
  • Note that the northeastern states like Meghalaya receive heavy rainfall, such as in Mawsynram, one of the wettest places on Earth, due to the combination of the southwest monsoon and orographic lifting from the Khasi Hills.

Temporal Variations in Precipitation

• Monsoon Season (June-September):
  • Discuss how the southwest monsoon is the primary source of rainfall, with different regions receiving varying amounts of precipitation.
  • Mention how the intensity of monsoon varies from heavy rainfall in the coastal areas to moderate or low rainfall in the interior regions.
• Northeast Monsoon (October-December):
  • Explain how this monsoon season brings relatively lighter rainfall, especially along the eastern coast and southern peninsula.
• Interannual Variability:
  • Discuss how phenomena like El Niño and La Niña affect the monsoon’s strength, impacting the distribution of rainfall from year to year.

Factors Contributing to Spatial and Temporal Variations

• Topography:
  • Explain how the presence of mountain ranges like the Western Ghats, Eastern Himalayas, and the Aravallis contributes to precipitation patterns through the orographic effect.
  • Mention regions with high altitudes like the Himalayas, which receive more rainfall due to orographic lifting.
• Indian Ocean Dipole:
  • Explain how the positive and negative phases of the Indian Ocean Dipole can enhance or reduce rainfall, respectively.
• Atmospheric Circulation:
  • Discuss the role of global atmospheric circulation, particularly the Intertropical Convergence Zone (ITCZ), in directing moist air to India.
  • Mention how the positioning of the jet streams affects precipitation.
• Latitude and Longitude:
  • Mention how India’s latitudinal extent (from tropical to temperate zones) results in varying climatic zones, influencing precipitation.
• Local Factors:
  • Highlight how factors such as proximity to large water bodies, urbanization, and deforestation can also impact precipitation at a smaller scale.

Conclusion

• Summarize the importance of understanding spatial and temporal variations in precipitation for water resource management and climate adaptation.
• State that accurate analysis of precipitation patterns can aid in better planning for agricultural, water management, and disaster response systems across India.

Relevant Facts

• Monsoon Patterns: The southwest monsoon (June-September) brings heavy rainfall to coastal regions, the Western Ghats, and the northeastern states. The northeast monsoon (October-December) brings lighter rainfall to the eastern coast and southern peninsula.
• Rain Shadow Effect: Regions such as Rajasthan and parts of the Deccan Plateau receive very little rainfall due to the rain shadow effect caused by the Western Ghats.
• Heavy Rainfall Areas: Mawsynram (Meghalaya) receives over 400 cm of rainfall annually, one of the wettest places in the world.
• Interannual Variability: The El Niño phenomenon often weakens the monsoon, leading to droughts, while La Niña enhances the monsoon, bringing above-average rainfall.
• Geographical Features: The Himalayas and Western Ghats contribute significantly to orographic rainfall. For example, the western slope of the Western Ghats receives heavy rainfall, while the leeward side remains dry.
• Indian Ocean Dipole: A positive phase of the Indian Ocean Dipole leads to enhanced monsoon rainfall, while a negative phase can result in deficient rainfall.