A day after the India Meteorological Department (IMD) attributed the record day-time temperature of 52.9°C in Delhi to a faulty instrument, another station in Nagpur incorrectly reported a temperature of 56°C on Friday.
The IMD said it was due to a “failure of electronic sensors”. As in the case of Mungeshpur in Delhi, the erroneous temperature was recorded at an automatic weather station (AWS) in Nagpur, Maharashtra.
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Unlike manually operated weather stations where personnel take periodic measurements of the temperature using thermometers, AWS rely on sensors that detect changes in temperature. While considered accurate, they are complex instruments prone to errors, which are harder to detect and rectify.
“The report of 56 C on 30/05/2024 is not correct and not declared officially,” the IMD said in a statement on Friday, “The temperature sensor at Nagpur City AWS, maintained by RMC Nagpur (Regional Meteorological Centre) is currently malfunctioning, and RMC Nagpur is working to fix it. However, it is important to note that electronic sensors can fail at extreme weather conditions. Automatic systems may report erroneous reading due to various reasons such as site conditions, damage of sensors or its protection shields etc.”
The statement added that the IMD staff were trained to detect such erroneous readings, and anomalous readings were filtered in the “pre-processing” stage. The actual temperature at Nagpur’s Central Institute for Cotton Research – located close to the aberrant AWS – was 44°C.
While a final report by the IMD on the malfunctioning sensors in Delhi is awaited, experts have said that all instruments – whether manual or automatic – require regular calibration much like weighing scales and manual watches, when they display erroneous values. “When values go outside a certain range, there is usually a quality control system in place to review the readings. We need to strengthen this system,” said M. Ravichandran, Secretary, Ministry of Earth Sciences, the parent organisation of the IMD.
