Recent extreme weather events across the world, including severe heatwaves in the western United States, increasing cyclone activity in the Arabian Sea, changing behaviour of Western Disturbances, and rising concerns regarding the Earth’s heat budget imbalance, highlight the growing significance of atmospheric processes in understanding climate dynamics. These phenomena are closely linked with temperature distribution, atmospheric circulation, condensation, rainfall mechanisms, ocean-atmosphere interaction and climate change.
A heat dome is a meteorological phenomenon in which a strong high-pressure system traps hot air near the Earth’s surface for an extended period. The trapped air behaves like a lid on a pot, preventing heat from escaping and causing temperatures to rise continuously.
Under high-pressure conditions, air descends and compresses. This compression increases air temperature and suppresses vertical movement. Since the warm air cannot rise, heat accumulates near the surface, producing prolonged and extreme heatwaves.
The formation of heat domes is closely associated with the jet stream. When the jet stream becomes stationary or develops large northward bends, high-pressure systems remain locked over a region for prolonged periods, intensifying heat conditions.
A Pyrocumulonimbus (PyroCb) cloud is an extreme thunderstorm cloud generated by intense heat sources such as:
These clouds evolve from pyrocumulus clouds when sufficient atmospheric instability and moisture are present.
Although these clouds can produce lightning, they generally produce very little rainfall. Lightning generated by PyroCb clouds can ignite new wildfires, making them highly destructive during forest fire events.
Normally, atmospheric temperature decreases with altitude. However, during temperature inversion, this normal lapse rate reverses and temperature increases with height.Normal Lapse Rate: Temperature decreases with altitude, but during inversion temperature increases with altitude\text{Normal Lapse Rate: Temperature decreases with altitude, but during inversion temperature increases with altitude}Normal Lapse Rate: Temperature decreases with altitude, but during inversion temperature increases with altitude
Temperature inversion creates highly stable atmospheric conditions and suppresses vertical air mixing.
Temperature inversions are more common in:
They are comparatively less common in tropical regions.
The Arabian Sea has witnessed a noticeable increase in cyclone frequency and intensity in recent decades due to changing climatic conditions.
The Arabian Sea has warmed significantly over the past few decades. Higher SSTs increase evaporation and atmospheric moisture, providing additional energy for cyclones.
| Cyclone | Year |
|---|---|
| Tauktae | 2021 |
| Vayu | 2019 |
| Mekunu | 2018 |
Vertical wind shear disrupts cyclone development by disturbing storm structure. A weakening of upper-level wind shear over the Arabian Sea has allowed cyclones to:
Cyclone Tauktae maintained its intensity for a prolonged period due to weak wind shear conditions.
Monsoon conditions are generally less favourable for cyclone formation because of strong wind shear. However, cyclones can still develop during the monsoon season under suitable conditions.
Pre-monsoon and post-monsoon seasons remain the most active cyclone periods.
Climate change has increased:
The Arabian Sea, historically less cyclone-prone than the Bay of Bengal, is now witnessing a significant rise in cyclone activity.
Western Disturbances (WDs) are extra-tropical weather systems originating in the Mediterranean region and moving eastward towards India.They significantly influence the onset and progression of the Southwest Monsoon.
When WDs persist during April–May, they delay monsoon onset by:
This delays the development of the monsoon circulation system.
Persistent WDs interfere with the southward shift of the:
This further delays monsoon onset.
Early withdrawal of Western Disturbances enhances monsoon development because:
Convectional rainfall occurs due to intense surface heating. Heated air rises, cools and condenses to form thunderstorms.
When moisture-laden winds encounter mountains, they are forced to rise, cool and condense, producing rainfall on the windward side.
| Region | Feature |
|---|---|
| Western Ghats | Heavy rainfall |
| Meghalaya | Extreme rainfall |
| Arunachal Pradesh | Orographic rainfall |
| Deccan Plateau | Rain-shadow region |
Leeward regions receive very little rainfall due to descending dry air.Examples:
Cyclonic rainfall is associated with:
Occur mainly between June and November in:
They cause heavy rainfall in coastal regions.
Western Disturbances bring winter rainfall to:
This rainfall is crucial for Rabi crops.
The Northeast Monsoon occurs from October to December.Tamil Nadu receives more than 50% of its annual rainfall during this season.
The Earth’s heat budget refers to the balance between incoming solar radiation and outgoing terrestrial radiation.However, this balance is increasingly disturbed due to rising greenhouse gas concentrations.
The tropical belt between 40°N and 40°S receives surplus solar radiation because sunlight is more direct.
Polar regions experience heat deficit because of:
The unequal heat distribution drives:
These systems redistribute heat from the tropics toward the poles.
Greenhouse gases trap outgoing longwave radiation, leading to:
The increasing concentration of greenhouse gases has created a long-term energy imbalance in the Earth’s heat budget.
| Topic | Key Idea |
|---|---|
| Heat Dome | High-pressure system trapping heat |
| Pyrocumulonimbus | Fire-generated thunderstorm cloud |
| Temperature Inversion | Temperature increases with altitude |
| Arabian Sea Cyclones | Intensified by warmer SSTs |
| Western Disturbances | Influence monsoon onset |
| Orographic Rainfall | Rainfall due to mountain uplift |
| Heat Budget | Balance of incoming and outgoing radiation |
Fast-flowing upper atmospheric winds influencing weather systems and monsoon behaviour.
A low-pressure belt near the equator where trade winds converge, playing a major role in monsoon circulation.
Variation in wind speed and direction with height. Strong wind shear weakens cyclones, while weak shear supports cyclone intensification.
Reflectivity of a surface. Ice and snow have high albedo and reflect large amounts of solar radiation.
Updated – 18 May 2026 ; 08:30 PM