Fog or air pollution? What's behind Dhaka's winter dreariness?

As winter deepens, daytime visibility has been steadily diminishing throughout the week. Monday brought a brief glimpse of the sun, but for the five days prior, it remained obscured across the country.

Experts believe the layer of haze blocking the sun's rays is unusual for typical winter fog.

They attribute it to a combination of pollution intermingling with fog, forming a dense veil obscuring the sunlight. This blend of fog and pollutants not only impedes daytime visibility but also intensifies the chill of winter.

According to meteorologist Md Abul Kalam Mallik, Bangladesh has been enveloped by dense fog akin to those in various regions of South and East Asia since Jan 11. Similar fog-blanketed parts of India, including Delhi, Uttar Pradesh, Madhya Pradesh, Bihar, West Bengal, as well as Myanmar and Thailand.

Mallik explained that the phenomenon arises from the inability of sunlight to sufficiently warm the earth's surface. "Dense fog develops when warm air hovers above cooler surface air. The surface and the air just above it are cold, and fog forms when air containing water vapour flows over this cold layer. At night, the surface cools further, exacerbating the fog upon daylight."

He refers to this as a 'stratus cloud' situation.

According to Malick, air currents carrying pollutants from New Delhi through Uttar Pradesh and Madhya Pradesh exacerbate the fog as they enter Bangladesh from the north and northeast.

Prof Ahmad Kamruzzaman Majumder, the founding director of Stamford University's Centre for Atmospheric Pollution Studies, contrasts this with normal winter fog, which would dissipate in sunlight, allowing it to reach the earth's surface.

"This fog is laden with smoke and dust, forming what we term 'smog'. This polluted fog generates the current weather pattern."

Elaborating on the characteristics of this smog, Majumder noted its greater density compared to regular fog. This density creates a stable layer extending three to four kilometres above the earth's surface, effectively blocking sunlight and casting a perpetual evening-like gloom.

He emphasised the urgency of reducing pollution to mitigate the situation, saying, "We can curb the addition of new pollutants. Without rainfall, curbing this pollution is challenging."

Mallik said that light rain is likely to occur around Thursday or Friday, which should raise night temperatures from Jan 20. "Such winter rains are typically induced by western low pressure systems," he added.

Majumder expects the rainfall to disperse the haze, allowing direct sunlight to reach the surface and re-establish atmospheric contact.

Highlighting the smog's presence in three atmospheric layers and its detrimental effects on humans, animals, and plants, Majumdar advised particularly vulnerable groups, such as the elderly, children, pregnant women, and those with respiratory issues, to take precautions like wearing masks and avoiding outdoor activities in these conditions.

RESIDENTS GRAPPLE WITH WINTER WOES

The Bangladesh Meteorological Department forecasts moderate to dense fog from midnight to morning, possibly lingering until noon in some areas. This fog is expected to disrupt air traffic, inland waterway transport, and road connectivity temporarily.

The cold and thick fog are causing significant difficulties for those who have to venture outdoors for work.

Transport workers, in particular, are facing challenges due to drastically reduced visibility.

Md Rafiq, a driver for a Rabrab Paribahan bus operating between Gabtali and Badda, pointed to a noticeable decline in passengers due to the winter conditions and fog.

"In the mornings, visibility is near zero. Driving becomes a risky guessing game. Fewer people are willing to travel unless it's necessary, leading to a sharp drop in passengers," he said.

Rickshaw driver Idris Hossain echoes these sentiments, expressing the hardship he faces in the fog and cold. "It's a tough situation. If I don't work, I can't eat. Winter is especially hard for the poor."

The impact of the foggy and cold conditions is being felt by people from all walks of life.

Students and office-goers are also struggling.

Afia Islam, a seventh-grader at Manipur High School and College, described the challenges she faces in getting to school. "Classes start at 7:30 am, but I have to leave an hour earlier. It's still dark and extremely cold then, and finding a rickshaw is difficult. This year, the fog is much thicker, making it very hard to travel to school."

Moushumi Das, an NGO worker, said, "I leave for the office around 7:30 am, either by CNG autorickshaw or motorcycle since cars aren't available. The air is bitterly cold, and in the dense fog, there's a constant fear of accidents since visibility is so poor."