What is a Heat Dome? Why Indian Cities aren’t Even Cooling Down at Night, Explained

Trying to catch a peaceful night’s sleep has become a way big expectations across the urban India lately. Even at midnight, you might experience a heavy blanket of hot air offering zero respite or relief from the daytime sun and heatwaves. 

According to recent reports from India Meteorological Department (IMD), multiple Indian cities have been registering minimum nightime temperatures well above 33°C. While we Indians are used to brutal summer afternoons, meteorologists explain that this round-the-clock roasting temperature is the signature footprint of a heat dome. 

To put it simply, this invisible climate phenomenon called heat dome, traps extreme heat close to the ground. It is primarily the reason behind why we have been robbed off of our natural nightly cooling cycles like good old day. 

But there’s more to learn about what is a heat dome and why it is affecting Indian weather alerts even at night this year. So hop on, and read hereonwards to find the answer. 

What is a Heat Dome?

Image Courtesy: Drishti IAS

As you can see above in the image, a heat dome functions through an oppressive cycle of atmospheric pressure, a direct result of gravitational pull of the Earth. Take a look at the following pointers to note how it is impacting our night time relief to understand it better: 

1. The change in movement of air globally allow a strong high-pressure system to settle over a region. 

2. During the day, the trapped hot air naturally expands and try to escape upward via convection. We know that convection is a process where transfer of heat happens in form of liquid or gas, which is unlikely to happen in a heat dome. 

3. The heavy high-pressure system in such cases acts like a cap that forces the rising hot air right back down towards the surface. 

4. As the trapped air sinks, it compress to release more heat. Compression packs the air molecules closer together to rise the already high temperature even further. 

In a normal weather, our surrounding regions or any other place on Earth spread its gathered heat back out into space. It helps the Earth’s surface temperature naturally to drop down when compared to daytime. 

However, under a rigid heat dome, the high-pressure lid remains firmly shut. The day’s superheated air will accompany you in the evening. And then follows the dangerously high nightime temperature. 

Why India Cities are Facing Warm Night Warnings?

We learnt just now that heat dome is an atmospheric phenomenon that happens miles above us. But its worst effects are concentrated on the ground across urban India due to a combination of many local factors. 

One of the many reasons we experience night heatweave in Indian cities are buildings constructed out of asphalt, concrete, and steel. These materials act like thermal bricks. Meaning, they absorb way more heat during the day than huts made of clay. 

Similarly, in coastal or river basin cities, the heavy air pressure gets sealed with surrounding moisture alongside the heat. And high humidity prevents human sweat from evaporating regularly. As a result, if you are living in any coastal city of India your body may experience a 34°C night closer to a suffocating 40°C.

Science says that a human body relies on cooler night temperatures to lower its core temperature and recover from daytime heat stress. But, if cities will continually fail to cool down after dark, cases of heat exhaustion, dehydration, and cardiovascular strain are likely to rise sharply. 

We also cannot ignore tha fact that global warming and constant climate change are resulting in such changes in our atmosphere constantly. Especially when heat domes are becoming standard summer weather rather than rare natural phenomena.

Adapting to this shift can be done through better city planning that prioritises cool roofing and expanding greeneries. Meanwhile following the official IMD evening weather warnings as a vital metric for public safety is a must for the masses.