The India Meteorological Department has warned of severe heatwave conditions affecting extensive areas of eastern India and the Gangetic Plain. As the world grapples with the waning phase of the strong El Niño of 2023.This highlights the challenge of understanding how global warming affects local weather. Additionally, the presence of anticyclones further complicates the situation, exacerbating the severity of heat waves in affected areas.
Role Do Heat Waves Play in Global Warming
- Heat waves result from climate change, caused by the burning of fossil fuels that add Greenhouse Gases (GHG) to the atmosphere.
- These gasses trap more heat energy, increasing average and extreme temperatures.
- GHG emissions from human activities have heated the planet by about 1.2 degrees Celsius since pre-industrial times.
- That warmer baseline means higher temperatures can be reached during extreme heat events.
- Global warming causes uneven temperature changes across regions, leading to local variations in heat waves.
- Despite some areas experiencing cooler temperatures, global warming can create conditions that intensify heat waves locally, influenced by land use and geography.
- Understanding these local effects is important for accurate forecasting and effective heat wave mitigation.
What is an Anticyclone
- High-Pressure Systems: Anticyclones are areas of high atmospheric pressure, the opposite of cyclones (low pressure).
- Wind Circulation: Winds blow clockwise around an anticyclone in the Northern Hemisphere and counterclockwise in the Southern Hemisphere due to Earth’s rotation (Coriolis Effect).
- Clear Skies and Calm Weather: Anticyclones bring stable, calm conditions with little wind and clear skies.
- Dry Air: Sinking air in anticyclones warms up and dries out, leading to less rain and humidity.
- Summer vs. Winter Effects: Summer anticyclones can be hot and sunny, while winter anticyclones can be cold and clear with morning frost.
Links Anticyclones to Heat
Anticyclones and Heat
- Anticyclones are linked to heat through their persistence and strength.
- During the pre-monsoon season, the Indian Easterly Jet (IEJ) and a strong westerly jet can generate an anticyclonic pattern over the Indian Ocean and the Indian subcontinent.
- A strong anticyclone can bring dry and hot weather over many parts of India, while a weak anticyclone produces milder weather.
- IEJ is a narrow belt of strong easterly winds in the mid-troposphere that blows over peninsular India and the adjoining south Indian Ocean during the pre-monsoon season (March-May).
- It is weaker and smaller than the well-known African Easterly Jet (AEJ).
- AEJ occurs in the lower troposphere over West Africa. It is characterized by easterly winds and is most prominent during the summer months.
- It is formed due to the temperature contrast between the hot Sahara Desert and the cooler Gulf of Guinea.
Impact of Anticyclones on Weather Patterns
- Strong IEJ years lead to higher near-surface temperatures and drier conditions in India, while weak IEJ years result in cooler and wetter conditions.
- The strength of the anticyclone in a particular year is a key factor in determining whether it is related to heat waves and global warming.
- The impact of El Niño on the Indian subcontinent tends to produce stronger and more persistent anticyclones, leading to longer-lasting and more intense heat waves.
- Understanding the background state of cool seasonal temperatures and strong, persistent anticyclones is essential for accurate weather predictions and early warnings.