45: Thermal Inversions Flashcards
What conditions make air pollution worse?
thermal inversions
What is a thermal inversion?
happens when a layer of cold air is temporarily trapped near the ground by a warmer, upper layer
What happens during a thermal inversion?
pollutants do not get dispersed
Is warm air less dense than cold air?
yes, warm air is less dense than cold air and it moves up
What are normal conditions of air?
during day: sun warms up air near surface, this air expands and rises, carrying low-lying pollutants higher
- under normal conditions there is constant movement of air
What is the simple definition of a thermal inversion?
sometimes, a layer of cold air is trapped below one warmer, less dense layer
What does warm air do?
prevents ascending air currents and the dispersion of pollutants (acts as a lid)
Where are thermal inversions common?
urban areas or in a valley
What are urban heat islands (UHIs)?
structures like buildings, roads, and other infrastructure absorb and re-emit the sun’s heat more than natural landscapes such as forests and water bodies
- urban areas become islands of higher temperatures
What do UHIs result in?
thermal inversions and more thunderstorms
What are dust domes?
pollutants are trapped on the city air (thermal inversions result)
What is Mexico City?
a megacity with over 22 million people in the metro area
(more people, more industries, more cars)
What does Mexico City’s location look like?
- it is at high altitude (solar radiation is intense)
- surrounded by mountains (air can be stagnant (does not move) with winter thermal inversions)
- deforestation and construction (exposed the soil to wind erosion)
- VERY polluted but doing better
What is the most polluted city in the world?
Seattle, USA
