Model Answer

Introduction

India experiences a highly variable distribution of precipitation, with significant spatial and temporal differences across the country. Around 80% of the nation’s annual rainfall occurs during the monsoon season, which plays a crucial role in agriculture and water resources. However, rainfall varies from over 400 cm in the northeastern states to less than 10 cm in arid regions like Rajasthan. Various factors, such as geographical location, monsoon systems, and topography, contribute to these variations.

Spatial Variations

• Monsoon Influence: The Indian monsoon is the primary driver of precipitation. The monsoon’s onset, progression, and retreat differ across regions, influencing the rainfall distribution.
• Northeastern States: These regions receive heavy rainfall year-round, including during the Northeast Monsoon (October to December), which brings additional precipitation.
• Coastal Regions: The western coast and northeastern regions experience substantial rainfall due to the southwest monsoon and the orographic effect caused by the Western Ghats and Eastern Himalayas.
• Rain Shadow Regions: Areas such as parts of Rajasthan and the Deccan Plateau receive minimal rainfall due to the rain shadow effect created by the Western Ghats and other mountain ranges.
• Himalayan Region: The Himalayas, particularly the foothills and higher elevations, receive heavy rainfall due to the orographic lifting of moisture-laden monsoon winds.

Temporal Variations

• Monsoon Season: The southwest monsoon, from June to September, brings the majority of rainfall, with varying intensities across different regions. The northeast monsoon (October-December) impacts the eastern coast and southern peninsula with lighter rainfall.
• Seasonal and Interannual Variability: Variations in the strength and timing of the monsoon occur due to climatic phenomena like El Niño and La Niña, affecting the precipitation distribution each year.

Factors Contributing to Variations

• Indian Ocean Dipole: This climate pattern affects the monsoon by influencing sea surface temperatures, which can either enhance or reduce rainfall.
• Topography and Elevation: Mountain ranges, such as the Western Ghats and Himalayas, cause orographic lifting, leading to enhanced rainfall on windward slopes.
• Atmospheric Circulation: Patterns like the Intertropical Convergence Zone (ITCZ) and jet streams direct moisture-laden air masses, affecting precipitation.
• Local Factors: Proximity to water bodies, deforestation, and urbanization also impact local rainfall patterns.

Conclusion

Understanding the spatial and temporal variations in precipitation is crucial for managing India’s water resources and adapting to climate change. By analyzing these patterns, India can implement better strategies for water conservation and sustainable development.

Model Answer

Western disturbances are extra-tropical storms originating in the Mediterranean region, which bring sudden winter rains to the north-western parts of the Indian subcontinent. These disturbances travel from west to east, powered by the Westerlies—prevailing winds between 30° and 60° latitudes. The disturbance forms in low-pressure areas over the Mediterranean Sea and moves across Iran, Iraq, Afghanistan, and Pakistan, before picking up moisture from the Arabian Sea. This moisture contributes to precipitation, especially over the Western Himalayan Region, and further extends to Nepal, Bhutan, and Arunachal Pradesh.

Impact on Indian Weather

• Precipitation and Rainfall: Western disturbances contribute to about 5–10% of India’s total annual rainfall. During the winter months (November to March), they bring much-needed rain and snow to the north-western regions of India, which are otherwise dry.
• Snowfall: Between December and February, these disturbances are the primary source of snowfall in the Himalayas, replenishing regional snowpacks and aiding in the storage of water resources for later use.
• Monsoon Onset: Western disturbances also influence the seasonal dynamics of the Indian summer monsoon. By modulating the snowpack and albedo (reflectivity) of the Himalayas and Tibetan Plateau, they impact large-scale atmospheric circulation patterns that affect the onset of the monsoon.
• Regional Effects: The impact of western disturbances stretches up to regions like Patna, Bihar, where the resulting rain benefits rabi crops such as wheat, mustard, and barley.

Conclusion

Western disturbances are essential for India’s winter precipitation, sustaining water supplies, influencing regional crops, and contributing to snowpack formation in the Himalayas. Their role in the broader climate system, especially in light of global warming, underscores the need for careful monitoring to safeguard agricultural productivity.

Model Answer

Local Winds

Local winds are winds that blow over a small geographical area, typically covering distances from tens to a few hundred kilometers. They are usually short-lived, lasting only several hours to a day, and are influenced by local geographic features like landforms and weather patterns.

Examples of Local Winds and Their Climate Impact

1. Land and Sea Breezes
   • Occur in coastal areas due to the differential heating of land and water.
   • During the day, sea breezes keep coastal areas cooler, while at night, land breezes make them warmer.
   • Impact: These winds moderate the temperature differences between day and night, affecting local climate.
2. Mountain and Valley Breezes
   • On sunny days, warm air rises from the valley to the mountain slopes (valley breeze).
   • At night, cooler air from the mountains flows down into the valley (mountain breeze).
   • Impact: These winds influence temperature fluctuations in mountainous regions.
3. Föhn/Chinook
   • Warm, dry winds descending from mountains, raising temperatures significantly.
   • Impact: They help in snowmelt, benefiting agriculture in areas like the Rockies and Alps.
4. Harmattan
   • A dry, dusty wind from the Sahara, bringing desert-like conditions and low humidity.
   • Impact: It reduces rainfall, harms crops, and causes dust storms in regions like West Africa.

Conclusion

Local winds can significantly affect the climate by altering temperature, humidity, and precipitation patterns, which in turn influences agriculture and daily life.