Anticyclones, hanging even now over India, link warming to heat
- April 29, 2024
- Posted by: OptimizeIAS Team
- Category: DPN Topics
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Anticyclones, hanging even now over India, link warming to heat
Subject: Geography
Sec: Climatology
Context:
- The latest advisory from the India Meteorological Department has warned of severe heat wave conditions affecting extensive areas of eastern India and the Gangetic plain for the upcoming days.
More on news:
- The complexities of the ways in which global warming manifests in local weather continue to underscore the need to model globally but predict locally.
- The waning phase of the strong El Niño of 2023 brings the expected warm temperatures across the globe — while cooler temperatures spread from Pakistan across India to West Bengal during March.
What do the heat waves have to do with global warming?
- Global warming also creates unique features locally that modulate heat waves on top of cool background temperatures.
- Heat waves over India have been of special concern this season because of the general elections. Some persistent circulation patterns have been creating heat waves and this pattern should serve as another focal point for improving predictions.
- It was apparent in March that the anticyclonic circulations over the North Indian Ocean were the drivers of unusual rainfall over Odisha.
- An anticyclone has winds moving in a clockwise direction, with air sinking down in the middle of it.
- As this air hits the ground, it is compressed and warmed and can create a high pressure heat dome.
- An anticyclonic circulation could also explain the historic Dubai floods of April 17.
What links anticyclones to heat?
- The persistence of the anticyclones is not unusual in and of itself. During the pre-monsoon season, the upper-level Indian Easterly Jet (IEJ) begins to take shape in the upper atmosphere, at around the 10 degrees N latitude, across the Arabian Sea, peninsular India, and the Bay of Bengal.
- A strong westerly jet exists to the north around 30 degrees N, and the two together can generate an anticyclonic pattern over the Indian Ocean and the Indian subcontinent.
- An easterly jet refers to strong winds coming from the east while westerly jets come from the west.
- These are natural seasonal features.
- The westerly jet is pushed north during the monsoon season and the IEJ dominates the Indian subcontinent.
- During the pre-monsoon season, a strong anticyclone can bring dry and hot weather over many parts of India while a weak anticyclone produces milder weather.
About Heat Waves:
- The Indian Meteorological Department (IMD) has given the following criteria for Heat Waves :
- Heat Wave need not be considered till maximum temperature of a station reaches atleast 40°C for Plains and atleast 30°C for Hilly regions
- When normal maximum temperature of a station is less than or equal to 40°C Heat Wave Departure from normal is 5°C to 6°C Severe Heat Wave Departure from normal is 7°C or more
- When the normal maximum temperature of a station is more than 40°C Heat Wave Departure from normal is 4°C to 5°C Severe Heat Wave Departure from normal is 6°C or more.
- When actual maximum temperature remains 45°C or more irrespective of normal maximum temperature, heat waves should be declared.
- Higher daily peak temperatures and longer, more intense heat waves are becoming increasingly frequent globally due to climate change.
- India too is feeling the impact of climate change in terms of increased instances of heat waves which are more intense in nature with each passing year, and have a devastating impact on human health thereby increasing the number of heat wave casualties.
What are the stages of early warnings?
- Returning to the local manifestation of global warming: accurate early-warning systems take a three-step approach called the ‘ready-set-go’ system, under the so-called ‘Subseasonal-to-Seasonal Predictions’ project of the World Climate Research Program under the World Meteorological Organisation.
- India is part of this project, has invested heavily in S2S predictions, and has made impressive progress in improving the accuracy of predictions.
- Preparing the system and guiding the National Disaster Management Agency (NDMA) requires this three-step approach to function efficiently and effectively.
- The ‘ready’ step provides a seasonal outlook — where the background state, or the external factors (such as global warming and the El Niño), are used to maximize the accuracy of longer-lead forecasts. The ‘ready’ step allows the NDMA, its local agencies, and all local governments to ready their disaster response systems.
- The subseasonal predictions refer to the extended range of weeks two to four, which contribute to the ‘set’ step.
- Resource allocations and identifying potential hotspots to move resources including personnel ensure disaster-preparedness is set to go.
- The ‘go’ step is based on short- (days 1-3) and medium- (days 3-10) range forecasts.