Weather and air quality are fundamentally linked. Sunshine, rain, air currents, and temperature all have direct influences on air pollution. Long days of sunshine during the summer catalyzes chemical reactions between pollutants, and higher wind speeds can disperse areas of concentrated pollution. Whether harmful or helpful, the weather's impact on air pollution is undeniable. Nowhere is this more evident than the event of a temperature inversion.
Also called weather inversions or thermal inversions, temperature inversions occur when the normal heat gradient of the atmosphere is reversed. Typically, air near the ground is relatively warm, and the atmosphere grows colder with elevation. Thermal inversions are more common than you may think. Ever wake up to see a blanket of fog in low-lying areas and dew on your grass? This is a sign of a temperature inversion. Temperature inversions usually disperse with wind, or when the surface begins warming again during the following day, but when temperature inversions stick around for a while, pollutants trapped beneath the lid of warm air can create hazardous air quality conditions.
There are several kinds of temperature inversion, including advection and subsidence inversion, but the most common type is a radiation inversion.
We will talk about what causes this type of thermal inversion below. These factors include:. The picturesque view of a clear winter sky over a snowed-in valley presents the ideal conditions for the formation of a thermal inversion.
Temperature inversions effectively put a lid on air pollution in an area. You might also like. Fog, mist and haze all affect visibility, which is an important part of forecasts affecting many aspects of life, from driving conditions to shipping and aviation. Read more. Coastal fog refers to the occurrence of fog over coastal regions, usually occurring in spring and summer.
It is also known as Haar and Fret in some parts of the UK. The ground becomes cooled quickly while the air above it retains the heat the ground was holding during the day. Temperature inversions also occur in some coastal areas because upwelling of cold water can decrease surface air temperature and the cold air mass stays under warmer ones. Topography can also play a role in creating a temperature inversion since it can sometimes cause cold air to flow from mountain peaks down into valleys.
This cold air then pushes under the warmer air rising from the valley, creating the inversion. In addition, inversions can also form in areas with significant snow cover because the snow at ground level is cold and its white color reflects almost all heat coming in. Thus, the air above the snow is often warmer because it holds the reflected energy. Some of the most significant consequences of temperature inversions are the extreme weather conditions they can sometimes create.
One example is freezing rain. This phenomenon develops with a temperature inversion in a cold area because snow melts as it moves through the warm inversion layer. The precipitation then continues to fall and passes through the cold layer of air near the ground. When it moves through this final cold air mass it becomes "super-cooled" cooled below freezing without becoming solid. The supercooled drops then become ice when they land on items like cars and trees and the result is freezing rain or an ice storm.
Although freezing rain, thunderstorms, and tornadoes are significant weather events, one of the most important things impacted by an inversion layer is smog. Smog is impacted by the inversion layer because it is, in essence, capped when the warm air mass moves over an area. This happens because the warmer air layer sits over a city and prevents the normal mixing of cooler, denser air. The air instead becomes still and, over time, the lack of mixing causes pollutants to become trapped under the inversion, developing significant amounts of smog.
During severe inversions that last over long periods, smog can cover entire metropolitan areas and cause respiratory problems for the inhabitants. Temperature inversions are more common during the winter in the northern hemisphere due to high pressure, clear skies, and long nights, which allow heat to dissipate easily from the ground. This leads to a phenomenon called winter smog , which is further exacerbated by homes burning wood and coal for warmth. Knowing the air quality where you live has become more important than ever.
At Breeze Technologies, our Citizen Portal provides real-time, hyperlocal information so that you can take the necessary steps in keeping you and your family safe and healthy. What is smog?
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