What is going on in our atmosphere when an inversion layer occurs overhead???

Question

I have heard that the L.A. basin is one such a place....Thanks for your answer...Tom Science 4

Answer 1

As you rise through the troposphere, the temperature falls - it gets colder as you get higher. Occasionally the temperature will rise instead of falling over a short distance. These rises are called temperature inversions. There are two causes.

The radiation inversion occurs on clear mornings. The ground cools by radiating infra red to space and this in turn cools the air above it. As the temperature falls to its lowest around dawn so does the air close to the ground cool down. This means that the air near the ground is cooler than the air immediatly above it and you have a temperature inversion. You can feel it on a clear night if you walk down a slope. The cold air collects at the bottom and it is warmer higher up. Radiation inversions can extend to, perhaps, a thousand feet above the ground.

Subsidence inversions are associated with high pressure systems. The Sub-tropical ridge is a belt of high pressure that lies around the globe in both hemispheres between about 30° and 40° north and south. Los Angeles lies under the ridge. In a high pressure system, air flows in at the top, descends and flows out at the bottom. Descending air warms as it is compressed. The rate at which rising air cools or descending air warms is greater than the rate of change of temperature with height (called the environmental lapse rate). This means that the descending air becomes warmer than air below it producing a temperature inversion.

Radiation inversions disperse as the air warms up after sunrise, subsidence inversions can last for days.

The air under an inversion is very stable and there is no upwards motion of air through the inversion. This means that any pollutants in the air under the inversion are trapped there until the inversion breaks. With radiation inversions this does not take long but subsidence inversions can keep the pollutants there for days.

Answer 2

You know how warm air rises and cold air falls? Well an inversion layer is where cold air ends up getting trapped under warm air. This causes a stagnation of the air. There is little or no wind, cause the air masses aren't falling or rising. This happens often in London, where it used to cause the "pea-soupers" or super dense smog. The pollution from factories wasn't blown out of London as usual because an inversion layer was preventing any airflow.