Context: Recently, Several parts of Europe have witnessed unprecedented winter heat wave caused by heat dome where temperatures had increased 10 to 20°C above normal. 

Heat Dome

• It is a weather phenomenon in which an area experiences stifling heat where atmosphere traps hot ocean air like a lid or cap a system, for an extended period of time.

• Heat is trapped by high-pressure prevailing over the region.

• It begins where there is a strong change (or gradient) in ocean temperatures.

• In convection process, gradient causes more warm air to rise over the ocean surface which is heated by the ocean surface.

• Weather conditions are clear sky and low humidity.

• It can typically last a week which ends when the formation becomes too big to keep standing and falls over which releases the trapped air and ending the swelter.

• It can also move to a neighbouring area.

Causes and formation of heat domes

• It results from a change in air temperature as it passes over land.

• It can occur when temperature of ocean rises in winter which causes air that passes over them to increase its temperature.

• Water closer to the jet stream is heated first as compared to water far away from that.

• Jet streams- are narrow wavelike bands of strong wind in the upper levels of the atmosphere which blows from west to east and meanders in north and south.

• As warmer air passing over ocean travels from west to east, it gets trapped on land and forms heat waves.

• Change in air temperature causes meandering of Jet streams to become bigger and moving far to the north which causes air to move slower or even become stagnant.

• This causes strong and high-pressure atmospheric conditions which leads to heat domes.

• High pressure causes this air to pile up and sinks which causes increase in temperature of air and it becomes drier.

• Once air reaches the ground, it gets compressed and becomes warmer.

• This high pressure causes heat dome to occur.

• Hot air cannot escape through the top of the dome because high atmospheric pressure.

• Longer the air remains trapped, more the sun heats the air which produces warmer conditions with every passing day.

• If air near the ground passes over mountains and then descends, it can warm even more.

Europe Heat dome

• It most commonly occurs when the temperature of the tropical Pacific Ocean rises in the winter.

• Because of climate change, the temperature of the western Pacific Ocean is higher than eastern Pacific Ocean.

• This temperature difference leads to warm air rising higher over the western Pacific and pushing colder air down over the eastern Pacific.

• Result- more hot air passes across the land.

• Prevailing winds move hot air east and northern shifts of jet stream trap this air and move it towards land, where it sinks to cause heat waves in Europe.

Effects of heat domes

• It leads to sudden fatalities for poor household.

• It can also damage crops, dry out vegetation and result in droughts.

• It can cause wildfires, which can destroy a lot of land area.

• It can cause various heat-related problems like- heat rash, heat stroke, and fainting.