Deepavali Day Pollution

Deepavali Day Pollution

Subject: Environment

Context: It was the cleanest Deepavali since 2015

Why was the air cleaner this time?

It was essentially because of meteorological conditions.

• High wind speed: It helped prevent the accumulation of pollutants.
• High Temperature: It is not yet cool enough for the air to trap pollutants in the lower layers(Temperature Inversion)
• Emission from firecrackers have been reported to have the following effects:
• a) The children breathe toxic air and suffer from nasal irritation and throat congestion. b) The smoke also irritates the eyes cause tears and redness. c) Bursting crackers may increase blood pressure and aggravate heart disease. d) Nausea, headache and giddiness are common effects of bursting crackers. e) Lung infections such as coughing, sneezing, respiratory disorders like asthma, wheezing often get severe during Deepawali festival. The pollution hazards such as the toxic smoke causes a lot of discomfort in breathing. f) The poisonous gas can also affect pregnant women adversely. It may also affect the mentally ill patients leading to depression, fear and stress.

Temperature inversion:

• Temperature inversion, also called thermal inversion is a reversal of the normal behaviour of decrease of temperature with increasing height in the troposphere.

Ideal Conditions for Temperature Inversion:

1. Long Winter nights: Loss of heat from the ground should be greater than incoming radiation.
2. Clear Skies: For unobstructable escape of radiation.
3. Calm Stable Air: No vertical mixing at lower levels.
4. Slow Movement of air: No transfer or mixing of heat.
5. Snow covered ground surface: Maximum albedo/reflection of insolation.

Types of temperature inversion:

There are four kinds of inversions: ground, turbulence, subsidence, and frontal.

1. A ground inversion (Surface temperature inversion) develops when air is cooled by contact with a colder surface until it becomes cooler than the overlying atmosphere.
2. A subsidence inversion (Upper surface temperature inversion) develops when a widespread layer of air descends, gets compressed and heated by the resulting increase in atmospheric pressure, and, as a result, the lapse rate of temperature is reduced.
3. A turbulence inversion (Intermontane valley or air drainage type temperature inversion) often forms when quiescent air overlies turbulent air. Vertical mixing carries heat downward and cools the upper part of the layer. Cold air slopes down the valley with upper layers relatively warmer.
4. A frontal inversion occurs when a cold air mass undercuts a warm air mass and lifts it aloft; the front between the two air masses then has warm air above and cold air below.

Effect of temperature Inversion

Inversions play an important role in determining cloud forms, precipitation, and visibility.

• An inversion acts as a cap on the upward movement of air from the layers below. As a result, convection produced by the heating of air from below is limited to levels below the inversion.
• Diffusion of dust, smoke, and other air pollutants is likewise limited. In regions where a pronounced low-level inversion is present, convective clouds cannot grow high enough to produce showers and, at the same time, visibility may be greatly reduced below the inversion.
• Inversions also affect diurnal variations in air temperature. The principal heating of air during the day is produced by its contact with a land surface that has been heated by the Sun’s radiation. Heat from the ground is communicated to the air by conduction and convection. Since an inversion will usually control the upper level to which heat is carried by convection, only a shallow layer of air will be heated if the inversion is low and large, and the rise in temperature will be great.
• It can cause temperature stability which stops upward/downward movement of air causing no rain and dry conditions.