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The agricultural economy of Pakistan is dependent on several climate-related factors including the weather. Fog as a weather phenomenon plays an important role in our economy. In winter, Punjab, Khyber Pakhtunkhwa and upper Sindh areas between December and February are affected by fog.
When the Siberian cold air comes from the high elevation into the low elevation (the eastern Himalayas or Tibet) it meets the warm and moist air from the south and southwest due to western disturbances approaching Pakistan and neighbouring India.
This situation together with the anti-cyclonic circulation already existing there helped the formation and persistence of fog in the area. The fog dissipated as a result of the shifting of the anticyclone over Pakistan towards the east due to the movement of the western disturbance.
The northwest branch of the flow results in heavy fog in the north of Pakistan. When the air near the ground is colder than the air aloft, the denser air near the ground will not rise and will remain in its original position. The atmosphere is said to be stable that is favourable for fog formation.
In the same way, under stable and dry conditions, dust particles suspended in the air are not easily dispersed, resulting in a haze. As cold air from the north recedes and day temperatures fall sufficiently, warm and humid air comes in from the sea.
During this time, the warm and humid air may be cooled sufficiently by the underlying cold surface. This condensation of water vapour into droplets and hence resulted in the formation of fog. Fog forms when the difference between temperature and dew point is generally less than 2.5 °C or 4 °F.
The persistence of fog duration is mainly associated with the effect of air pollution. The regions of Punjab and Sindh comprise major agricultural fields in the country which also take part in fog formation as soil conditions have an important role in radiation fog formation.
The aerosols analysis reveals that the north-eastern part of Pakistan has been dominant by fine mode aerosols most probably due to their transport from biomass burning in Indo-Gigantic Plains (IGP) from October to November. This burning produces a large number of smoke aerosols with high optical depth.
The higher concentration of aerosols amplifies the duration/intensity of fog in Pakistan but only under favourable meteorological conditions. It has been noted that the trans-boundary pollutants have adverse impacts on the environment of Pakistan and cause dense fog formation in agricultural areas of Punjab and Sindh.
For the last few years, we are witnessing that the phenomenon of fog is getting stronger, which is engulfing the highways and motorways with full command.
Fog may be synonymous with danger and moral blindness for drivers and pilots. The first and foremost thing that is required for driving and flying is good visibility.
The motorway was closed due to severe fog, to all kinds of traffic from on motorways, M2 Lahore Thokar Niaz Beg to Pindi Bhattian, M3 Pindi Bhattian to Faisalabad and M1 Peshawar to Rashkai interchanges.
Accident ratio increases drastically during foggy conditions as visibility is adversely hampered by it resultantly, many precious lives are lost and property worth millions is destroyed. Even if a flight is taken during foggy conditions, its landing becomes almost impossible from a safety point of view.
Pakistan receives a heavy amount of sulfur dioxide, from coal-burning industries of India, which is adjacent to northeastern parts of Pakistan. During the foggy days in Lahore, the concentration of sulfate was exceptionally high and suggested that fog may be caused by the high SO2, and it is the main component of fog. These trans-boundary pollutants result in severe foggy conditions in Punjab.
Two major sources of aerosols in Pakistan are, dust blowing from deserts in either local or neighbour countries like Iran, Afghanistan and northern Africa, and other is biomass burning activity across Pak-India trans boundary especially in the latter half of the dry season.
The main source of the pollutants in our lower atmosphere is Eastern Punjab where all the coal-based industries are centered across the border in India. In places near irrigation canals, rice paddies, and rivers where there is more moisture available, the fog gets even thicker.
The prevalence of little or almost calm air over fog-affected areas and industrial development is also one of the central causes for the increase in pollutants in the atmosphere over the last three decades.
Air pollution is an issue that needs to be urgently addressed. In the winter months, with delayed rainfall, the cold and continuously dry conditions concentrate all the pollutants in the lower levels of the atmosphere, causing the smog to spread all over Punjab.
There is a need for a comprehensive action plan to address worsening levels of pollution throughout the country in which government and media will have to play a pivotal role. The government also has made the top agenda about to overcome the fog condition in Pakistan by rising in the relative humidity.
Rezwanullah, School of Management and Economics, at Beijing Institute of Technology also contributed to this article.