Strong winds lift upper fog, improve air quality in Delhi

Wednesday’s peak temperature was logged at 15.2 degrees Celsius (°C) at Safdarjung, better than Tuesday’s 13.4°

Strong, icy winds broke the stubborn dense fog — prevalent at the upper level over the northern plains for nearly three weeks — on Wednesday and aided the dispersal of pollutants, improving the Capital’s air quality to “poor” (273) from Tuesday’s “very poor” (343), the India Meteorological Department said.

At Shahabad Mohammadpur Railway Station in the city on Wednesday morning. (Vipin Kumar/HT Photo)

These winds, blowing at steady speeds between 15km/hour to 18km/hour throughout the day made the Capital uncomfortably chilly though the maximum the mercury reached was higher compared to Tuesday.

Wednesday’s peak temperature was logged at 15.2 degrees Celsius (°C) at Safdarjung — representative of Delhi’s weather — better than Tuesday’s 13.4°C but still four degrees below normal for this time of the year and just 0.5 degrees shy of the “cold day” classification.

According to IMD, a “cold day” is when the maximum is 4.5°C or more below normal, and the minimum is below 10°C. To be sure, isolated parts of the city still recorded “cold day” conditions, including Palam with a maximum of 12.7°C.

Wednesday’s daytime cold also pushed power demand to the highest ever in the Capital during the winter months — at 5,611 MW at 11.08am — according to data from the State Load Despatch Center (SLDC). The previous peak draw was 5,559 MW recorded on January 5.

“We had strong winds, touching 18km/hour during the day and they helped uplift fog. Satellite images showed fog was blown away from large parts of northwest India during the day, allowing sunlight to come through and the maximum to rise,” said Kuldeep Srivastava, scientist at IMD.

Srivastava added that wind speeds should touch over 12km/hour on Thursday, making for another sunny but chilly day. The maximum is forecast to touch 17°C on Thursday.

Delhi’s 24-hour average air quality index (AQI) was recorded at 273, according to the Central Pollution Control Board’s national bulletin at 4pm. The last time it was “poor” was on December 20, when the average AQI was 285. The air quality has hovered between “very poor” and “severe" over the last three weeks.

The minimum on Wednesday was 7.1°C, which is normal for the year. It is forecast to hover between 6-7°C over the next three days.Srivastava added the chill and low temperatures in isolated areas were down to cold northwesterly winds, which will continue for a few days. “In areas where the sun was missing, the maximum was lower,” he said.

Since the start of the year, low temperatures and dense fog with wind speeds not exceeding 5km/hour have made for “cold day” to “severe cold day” conditions.

The maximum has not gone beyond 19°C on any day in January, and the minimum has been below 10°C since Jan 2.