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Delhi's 52.9 Degree Reading Probably Due to Sensor Error

By Sanjeeb Mukherjee, Ashish Tiwari
May 31, 2024 15:18 IST
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The Met blamed the malfunctioning of sensors kept at the Automated Weather Station for the gaffe.

IMAGE: A man drinks a cooling drink offered by locals in Narela, Delhi. Photograph: Priyanshu Singh/Reuters

On Wednesday, May 29, 2024, the India Meteorological Department said Mungeshpur, on the outskirts of Delhi, recorded an all-time high temperature of 52.9 degree Celsius, which is an abnormal reading.

The reading immediately went viral and became the talk of the town. The Met quickly corrected it and blamed the sensors at the Automated Weather Station (AWS) for the howler.

It has ordered an investigation into it and has stationed a team of senior scientists to ascertain its cause.

The error has put a spot of doubt also on Tuesday's highest reading for the city -- 49.9 degree Celsius -- also in Mungeshpur.


So in what conditions does an AWS malfunction? And how is it different from a thermometer-based temperature reading?

Experts say between the two, thermometer-based reading, which in the case of Delhi is done at the Safdarjung observatory, is a more reliable measurement due to the nature of the device.

This is not to say that an AWS does not give correct measurements but it is prone to going wrong if not calibrated properly, placed wrongly, or if the exposure is not correct.

The enclosure where the thermometer is kept, like the one at the Safdarjung observatory, is called a 'Stevenson Screen'.

This is nothing but a wooden box-shaped enclosure used to protect meteorological instruments against precipitation and direct heat radiation from outside sources, while allowing air to circulate freely around them.

IMAGE: Commuters use scarves to shield themselves from the heat on a hot summer day in Gurugram. Photograph: ANI Photo

Dry bulb and wet bulb thermometers in the 'Stevenson Screen' are placed vertically while the maximum and minimum thermometers are kept in a horizontal position.

The wooden box opens on the north side so that it is not exposed to direct sunlight.

"This helps in measuring temperature accurately," Mahesh Palawat, vice-president, meteorology and climate change, in private weather forecasting agency Skymet, told Business Standard.

Oon the other hand, Palawat said, an AWS was a sensor-based device and although its installation is also done in accordance with prescribed standards sometimes due to paucity of space the sensors are not accurately calibrated with the actual readings.

Also, if maintenance is not proper and the AWS is placed in an inappropriate place such a rooftop or over a concrete structure it tends to be affected by the nearby topography and overheat.

He said it was natural for an AWS to overheat but then the scientist who had taken the reading should have been careful before making it public.

Half a century is just a number as Delhi's Mungeshpur makes history

About 90 minutes drive from Connaught Place took Ashish Tiwari to Mungeshpur, bordering Haryana, on Thursday.

Sanjay Kumar, a farmer who also runs a grocery shop, reacts to the sudden media interest in his own way.

"This heat is not something new that we have encountered," he says.

He adds in a matter of fact way that almost everyone in this village has air conditioners and nobody ventures out during hot afternoons such as these.

This non-descript village in north-west Delhi, with a population of less than 3,500 according to the last Census, courted prosperity in recent years through sale of agriculture land for construction of factories and new age real estate projects. But that's not why it's in the headlines.

Mungeshpur's automatic weather station on Wednesday recorded India's highest-ever temperature of 52.9 degrees Celsius.

However, officials at the India Meteorological Department have revised it downwards.

The blazing heat may not be a problem for those like Sanjay Kumar, but it's a challenge for those working in the industrial area.

"Most of us come from neighbouring villages," a labourer points out.

The industrial zone has micro, small and medium scale enterprises making rubber products, tin items, plastic bottles etc. All of them energy guzzling and smoke spewing.

Delhi Lieutenant Governor Vinai Kumar Saxena on Wednesday had ordered paid leave to workers at construction sites from noon to 3 pm. But few know about it.

It's past noon and near the industrial area, several construction workers are resting: "Just for an hour we will rest and then resume work," says Ramesh, the youngest of the lot. When asked about the LG's order, they wondered if it was fake news.

"But even if my contractor gives me this relief, he wouldn't pay me for these hours," says Yogesh Sahu, a migrant from Chhattisgarh.

"Per day we get Rs 800. If any contractor doesn't pick us up by 9 or 10 am, the day goes for a toss and we have to return home empty-handed."

Tarun, their contractor, who has not heard of the '12-3 pm rule' says, "I am aware of the extreme heat situation. But I also have to fulfill the targets set by my boss... If they do not come to work, I will find many replacements at the chowk."

A worker has just recovered from high fever and is back at work. "My body got so heated up that I fell on this mud pile. Then my fellow workers took me to the nearest clinic... But now, I am fit for work," he says.

For Jogindar (34), working at a toll booth, just a table fan is a blessing.

He has a 10x10 room for himself, where he must complete his eight hour shift.

"For relief from this heat, my boss has given me two cold water canisters and a table fan," he says.

It's another matter that the power demand skyrocketed on the hottest day in Mungeshpur and the transformer blew up. Power was restored after several hours of sweat.

Apart from a mohalla clinic, there's no hospital in this village.

Dr Abhishek Garg, senior consultant at the clinic, says there's no case of heat stroke yet.

He says having a hospital in such a small village could be a waste of resources.

The International Labour Organisation in a 2019 report had said India will be one of the most affected countries from heat stress.

India has lost 4.3 per cent of working hours in 1995 and is projected to lose 5.8 per cent of working hours in 2030.

Oblivious of such data, Rajesh, a Delhivery executive, stops at the Mungeshpur village circle at around noon.

He complains about the heat while enquiring about an address. "Of course, my whole body burns while riding, but afternoon is the only time I get my consignments. So, there is no option, but to get the work done."

With inputs from Shreya Jai

Feature Presentation: Rajesh Alva/

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Sanjeeb Mukherjee, Ashish Tiwari
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