Foggy February: Experts explore ‘unusual’ weather
While wind speed this month has been calmer, February also saw more polluted days as compared to same month last year
The national Capital region, as well as parts of western Uttar Pradesh, has been seeing an unusually dense cover of fog in the morning and evening hours this month, leaving commuters stuck and weather analysts perplexed. Scientists said they are still exploring reasons behind this phenomenon which is not a common occurrence for this time of the year.
The analysts stated that while the wind speed this month had been calm and the impact of western disturbances low – a weather system that causes rains or snowing in the Himalayan states and subsequent rains or thundery development over the NCR – the month also saw more polluted days as compared to the same month last year, which some believe could be a plausible reason or a contributing factor.
“Never has such dense fog been seen over larger areas simultaneously for longer duration daily – upto nine-10 days – after February 10 in any winter season, even in Delhi or any airport at this belt, including Amritsar and Lahore,” said RK Jenamani, senior scientist, national weather forecasting centre, India Meteorological Department (IMD)
“We get dense fog in February but for a few days of the first week only, when the winter season has some features favouring it. This time, however, this spell has occurred when the night temperatures were two-three degrees Celsius above normal, which is something unique,” the senior scientist added.
Fog cover is considered shallow when visibility is upto 500 metre, moderate when it is up to 200 metre, dense when visibility is up to 50 metre, and very-dense when visibility is below 50 metre.
The IMD scientists said that this “unusual phenomenon” that had affected regions around Delhi to Lahore, has so far in February seen 23 hours or five mornings of fog dense enough to affect flight operations at the Indira Gandhi International Airport (IGI airport), against 28 hours (seven mornings) in December 2020 and 43 hours (ten days) in January this year.
Interestingly, the average dense-very dense fog frequency for the IGI airport for February is usually around 12 hours (three mornings).
The phenomenon had also been seen at other airports including at Lucknow and Amritsar, says RK Jenamani, senior scientist, national weather forecasting centre, IMD.
Stating that air pollution could be one of the contributing factors but not the entire cause, the weather scientist believes that moisture, low winds and near average minimum temperature are the reasons behind the foggy month.
“Absence of an active western disturbance in the northern plain areas leads to an anticyclone or a high pressure belt, leading to calm winds or light winds in the areas at lower levels, which form the top criteria fulfilled for dense fog to stay longer over this region,” added Jenamani.
For Monday, the Met department had forecasted dense to very-dense fog over Haryana, Punjab, Delhi and north-west UP.
“Dense fog over isolated pockets is very likely in Punjab, Haryana, Chandigarh, Delhi and north-west Uttar Pradesh on the morning hours of February 22,” stated the IMD’S bulletin.
According to data from the Central Pollution Control Board (CPCB), Noida in February 2021 saw 16 days of ‘very poor’ air quality and one day of ‘severe’ air quality so far, against only five days of ‘very poor’ air quality in February 2020.
Jenamani further said that more intensive study is required to understand the phenomenon in a better way.
“More analysis is needed to get all the answers around such unusual occurrences. There are already studies done for the period of 2015 to 2021 on fog at IGI, but by looking at the current condition, the study needs to be expanded to other areas as well. So we can in future understand and prepare to tackle the situation that hinders commuting,” said Jenamani.
According to weather analysts, commuters taking to the Eastern Peripheral Expressway, Yamuna Expressway and the Taj Expressway must avoid the early hour drives on these stretches as thick fog is most likely to slow them down by cutting the visibility.
“Either avoid or take caution while taking the expressways up to at least 9am for the next few days as foggy conditions may go on for a few days. The phenomenon may go on and off as winds speeds are likely to vary,” said Mahesh Palawat, vice-president, meteorology and climate change, Skymet.
Motorists said the heavy fog conditions are proving to be a hindrance to their commuting plans.
“It took me over five hours to reach Karnal via the Eastern Peripheral Expressway (EPR), which usually takes not more than three hours. Due to the farmers’ agitation, I chose to avoid the Singhu border and instead opted for the EPR via Ghaziabad to go to Shimla. However, as soon as I hit the EPR at Duhai around 5.30am, the fog was so dense that I couldn’t drive at more than 10-20 kmph for the entire stretch upto Rai,” said Anil Bhasin, a resident of Gulmohar Park in Delhi, who was commuting to Shimla on Saturday morning.
AIR QUALITY IMPROVES
Meanwhile, with varying wind speeds, the average air quality was recorded in the “poor” category across Ghaziabad, Noida, Greater Noida.
Pollutants PM 2.5 and PM 10 were also present in the air of the five immediate neighbours of Delhi, according to the air quality index (AQI) maintained by the CPCB.
According to the index, an AQI between zero and 50 is considered ‘good’, 51 and 100 ‘satisfactory’, 101 and 200 ‘moderate’, 201 and 300 ‘poor’, 301 and 400 ‘very poor’, and 401 and 500 ‘severe’.
The average 24-hour AQI at 4pm on Sunday was 260 in Ghaziabad, 300 in Greater Noida, 251 in Noida, according to CPCB
The CPCB states that an AQI in the “very poor” category may cause respiratory illness to people on prolonged exposure, while “poor” may cause breathing discomfort to most people on prolonged exposure.
On Saturday it was 336 in Ghaziabad, 324 in Greater Noida, 269 in Noida, 248 in Faridabad and 258 in Gurgaon.
The AQI for each city is based on the average value of all monitoring stations there. Ghaziabad, Gurgaon and Noida have four such stations while Greater Noida and Faridabad have two stations each, according to the app.