Nagpur Burns at 56°C After Delhi Hits 52.9°C; IMD Issues Heat Alert

Two out of the four automatic weather stations (AWS) set up by the IMD in Nagpur recorded unusually high temperatures, exceeding 50 degrees Celsius, even higher than the record-breaking temperature at the Mungeshwar AWS in North-West Delhi.

The temperature was measured at the Jawahar Navodaya Vidyalaya, located in Mungeshpur village, which also doubles as an automatic weather station (AWS).

The Delhi station caused a stir across the country after recording a historic 52.9 degrees Celsius. However, according to the IMD's AWS/ARG (automatic rain gauge) networks, the data from Mungeshwar is currently under scrutiny.

The Nagpur AWS, located in the middle of a 24-hectare open agricultural field belonging to PDKV at Ramdaspeth, off North Ambazari Road, recorded an astonishing 56 degrees Celsius. The AWS at the Regional Meteorological Centre (RMC) at Sonegaon also recorded 54 degrees Celsius. The AWS in the fields of the Central Institute of Cotton Research (CICR) at Khapri, off Wardha Road, showed 44 degrees Celsius. The Ramtek AWS also showed 44 degrees Celsius.

After the heatwave in Delhi, which is believed to be India's highest maximum temperature, the AWS/ARG networks are again in the spotlight. Regional meteorological officials stated that the AWS data should not be relied upon for extremely hot days, as the sensors start malfunctioning beyond 38 degrees Celsius.

It turns out that AWS sensors tend to act up when the temperature gets really high. Apparently, they work fine for temperatures below 38-40 degrees, but beyond that, they start getting wonky. According to a senior forecasting scientist at the RMC, this is known as a positive bias in scientific terms. The expansion of necessary elements needs to be linear, but this process loses its linearity at high temperatures.

A recent study found that the maximum temperature in the city varies a lot, depending on factors like densely populated areas, open areas with green cover, and open areas without plantation. The study highlighted that Nagpur has local climate zones, and the temperature varies significantly in each of them.

When TOI visited the PDKV AWS, they found that the temperature in the open field seemed to be higher than near the green cover of Maharajbagh Road. The sensors of the AWS were completely exposed to the scorching sun without any greenery around.

A senior RMC official mentioned that the AWS sensors are imported from European countries, where temperatures don't rise as high as in Indian cities.

ML Sahu, deputy director of RMC, said that the daily weather updates prepared for public consumption are done manually by scientists, and this manual data is considered to be more reliable.

"We use four mercury-based thermometers to record the daily temperature. A dry mercury bulb is used for the current temperature, and a wet bulb is used for measuring humidity. The temperature area is enclosed, and only air passes through it," Sahu explained.

The AWS data is transmitted to the Pune data centre, where the codes are interpreted and uploaded to the AWS/ARG networks portal in real-time.