Just hours after one of the automatic weather stations in Delhi showed a record-breaking temperature reading of 52.9℃ on Wednesday afternoon, the India Meteorological Department (IMD) has retracted the data, stating it could have been a “faulty reading".
The Automatic Weather Station (AWS) is among the 15 such stations recently installed by the weather department across Delhi-NCR for 24-hour temperature and rainfall observations. This is in addition to the five main department observatories where data is manually recorded and examined.
“It was most likely a faulty reading," says M Mohapatra, Director-General of Meteorology (DGM) late on Wednesday. “The data is from one of the newly-installed Automatic Weather Station (AWS) which continuously records temperature all through the day. While the temperatures can be high, it seemed like an outlier when compared to readings from other weather stations of the day." It recorded a temperature of 49.9℃ the day before.
How IMD Measures Temperature Data?
Unlike IMD’s departmental observatories in each state, where temperature is manually measured by IMD officials using their instruments like thermometer after every three hours, the Automatic Weather Stations (AWS) record temperature/humidity/wind speed and other weather data all through the day using its automated sensors with no manual intervention. The AWS have the advantage of providing real-time observations for local areas, and the weather department is in the process of further strengthening this AWS network across India to provide local weather forecasts. However, the maximum temperature of the day is measured around 2:30 pm when mercury usually peaks.
No other station in Delhi has recorded a temperature over 50℃ so far. The department’s weather observatory at Safdarjung, which remains Delhi’s oldest observatory functional since 1931, recorded 46.8℃, while it was 47℃ in Palam (set up in 1956) and 46.8℃ in Ayanagar (set up in 1967). The mercury has been hovering nearly 5-6℃ above-normal across all five of the oldest meteorological stations in Delhi for the last three days.
The temperatures which normally remain around 42-44℃ at this time of the year crossed 46℃ and settled there for consecutive days leading to blistering heatwaves across the national capital. So, it perhaps came as no surprise for many, when the IMD reported a temperature of nearly 50°C in Delhi’s Mungeshpur on Tuesday — until the reading soared to 52.9℃ the day later causing a tinge of disbelief.
“It is not official yet. Temperature of 52.3℃ in Delhi is very unlikely. Our senior officials in IMD have been asked to verify it," tweeted Union Minister Kiren Rijiju around 8 pm on Wednesday. Soon after, the IMD issued a statement admitting that the 52.9℃ reading was an outlier, and could have been “due to error in the sensor or the local factor", and it will examine its data and sensors.
ONLY FIVE CLIMATE REFERENCE STATIONS: IMD CHIEF
“We have five main climate reference stations across Delhi – Safdarjung, Palam, Ayanagar, Lodhi Road and Ridge. The data is manually recorded, and we have records of more than 70 years. So, it is urged that we use this data for any climate-related trends and extremes over Delhi," added the IMD chief.
According to Mohapatra, the five stations have well-defined environmental conditions which have not changed over the years significantly, so the observations are not affected much by temporary variations.
Normally, the temperature is recorded every three hours in the manual observatories, with the main reading around 2:30 pm – when mercury peaks in the day. However, the automatic weather stations measure the temperature all throughout the day. In 2022, the IMD had started including temperature and rainfall data from the 15 AWS along with the five departmental observatories. Additionally, temperature over urban areas like Delhi may also vary from place to place due to local conditions including green cover, concrete areas, proximity to any water body and barren land.
HEATWAVES TO REDUCE OVER NORTHWEST INDIA
As forecasted earlier by IMD, India has certainly borne the brunt of unusually higher number of heatwaves this summer, with temperatures surging to nearly 50℃ in Rajasthan. The heatwaves have swept Northwest India since May 17, with higher-than-normal temperatures during the day as well as night.
But the region including Delhi is expected to witness some temporary relief from the scorching heatwaves May 30 onwards, with thunderstorm activity/light rain which has already begun across the National Capital Region (NCR). A western disturbance has impacted the region, and is expected to bring down temperatures by 2-3℃ over the next few days with the help of some cooler, moisture-laden south-westerly winds from the Arabian Sea which are now blowing towards Northwest India. This will not only reduce the intensity of heatwaves, but also their geographical spread, said IMD on Wednesday.
