12 April 2025 : Daily Answer Writing
Q1) What are the characteristics of anticyclonic circulations, and how do they influence weather patterns over the Indian sub-continent? (10 marks, 150 words)
ANSWER
An anticyclone is a high-pressure system where air descends and moves outward. Surrounded by closed isobars, these systems rotate clockwise in the Northern Hemisphere. The recent anticyclonic circulation over the North Indian Ocean led to abnormal rainfall in Odisha in March 2024. They can also create heat domes that trap warmth.
Characteristics of Anticyclonic Circulations
- High Pressure Centre: Caused by descending air, leading to higher pressure at the core.
- Outward Flow: Air moves from the centre to the periphery due to pressure gradient.
- Wind Orientation: Clockwise in the Northern Hemisphere, anticlockwise in the Southern Hemisphere.
- Circular Motion: Coriolis force deflects winds—rightward in the north, leftward in the south—creating circular systems.
- Descending & Warming Air: Sinking air compresses and heats up, causing dryness.
- Clear Skies: Due to inhibition of cloud formation by descending warm air, leading to fair weather.
- Seasonal Effect: Summer anticyclones bring heatwaves; winter ones result in clear, cold conditions with frost.
Impact on Weather Patterns in Indian Subcontinent
- Heat Budget & Climate: Clear skies allow maximum solar heating, raising daytime temperatures, especially in winters.
- Ferrel Cell Influence: Located in the Ferrel cell, India’s weather is shaped by anticyclonic and cyclonic interplay, affecting monsoon timing.
- Desert Formation: Subtropical highs over the Arabian Sea contribute to the arid climate of the Thar Desert.
- Temperature Inversion: Winter subsidence leads to inversion layers, trapping pollutants and causing fog and health issues.
- Monsoon Modulation: Anticyclones influence El Niño/La Niña dynamics, which affect monsoon strength and distribution.
- Pre-Monsoon Heatwaves: Persistent anticyclones over the Indo-Gangetic plains cause extreme heat and can delay monsoon onset.
Anticyclones are not just fair-weather systems—they have far-reaching effects on India’s climate and extreme events. From supporting desert ecosystems to influencing rainfall and heatwaves, their role in atmospheric stability and climate dynamics is both complex and vital.
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