Effects of stratospheric wildfire smoke on ozone depleting substances and ozone levels in the northern midlatitudes

Abstract

The goal of this project was to examine whether there are correlations between recent wildfires in the northern hemisphere and stratospheric ozone anomalies in the midlatitudes following the creation of ozone depleting substances. To achieve this goal, data from the Aura satellite's Microwave Limb Sounder instrument was used and processed with self-written Python scripts.

Firstly, in order to analyze the data appropriately and to set it into context, results of previously published papers regarding the 2019-20 Australian wildfire were verified with the data. As a result, perturbations in hydrogen chloride, chloromethane, and ozone following the fires were found. The underlying chemical mechanism can possibly be explained by the hydrogenation of smoke particles and subsequent reactions on their surfaces. As an example for the northern hemisphere, the 2017 wildfire in British Columbia was analyzed in accordance with these findings. The process resulted in no connections between the Canadian wildfire and ozone destruction produced by ozone depleting substances being found in the data.

Therefore, in conclusion, there might be a certain threshold in injected smoke particle mass into the stratosphere. The injection of the Canadian wildfire was then potentially not enough in order to invoke sufficient production of ozone depleting substances compared to the initial production of ozone by smoke particles to deplete the midlatitude ozone layer measurably.

Popular Abstract

Ozone is essential for life on Earth as we know it. But why is that? Its chemical formula O3 does not look that different from normal O2 (dioxygen) that we humans need to breathe and live. But it actually gives the ozone a feature that makes it essential for our Earth. It can absorb ultraviolet light. This is the part of the Sun's light that causes sunburn. It is very powerful and is harmful not only to humans and animals but also to plants and, therefore, crops. The part of the atmosphere that holds most of this gas is the stratosphere. It sits about 15 to 50 km above the ground, and the ozone layer mostly sits in the lower part of that. It is like a shield that used to surround the whole Earth. But in the 1980s, researchers were shocked when they found out that there was a hole in this protective layer. Right above Antarctica, there was barely any ozone left. The cause of this ozone depletion were ozone depleting substances that were, for example, used as cooling agents in refrigerators. By 1987 it was agreed by 198 countries in the so-called Montreal protocol that the dramatic destruction of the Earth's protective ozone layer had to be addressed, and they pledged to themselves to rule out the production of many of these chemicals. The ozone hole over Antarctica is now slowly recovering and expected to be gone by the 2050s.

But there is another threat arising -- literally. Huge wildfires, as we saw in Australia in 2019-20, can produce smoke clouds that reach up into the stratosphere and might destroy ozone there. Chemical reactions with atmospheric chlorine that are induced by the smoke particles of the fires can deplete ozone. Some studies have already proven that the 2019-20 fire in Australia, which was the largest wildfire in recent history, damaged the ozone layer.

The goal of this project was to study whether large wildfires in the northern hemisphere, like the ones in Canada in 2017, also could have damaged the ozone layer in the midlatitudes or not. This region is especially interesting because most of the world's population lives in the northern midlatitudes, and therefore, an ozone loss there could hurt the lives of many people. In order to answer that question, satellite data was analyzed with self-written programs. First, the abundances of ozone and substances that destroy ozone for the 2019-20 Australian wildfires were analyzed and compared with results from earlier studies about it. An increase in the concentration of ozone depleting substances and a decrease in ozone concentration in the stratosphere were found in this region after the fire. The most popular theory on how wildfires actually influence the ozone is that smoke particles from big wildfires can reach the stratosphere and are then coated with water and sulfuric acid. These particles then invoke chemical processes which create substances that destroy ozone.

With the knowledge about the Australian fire as a baseline, the satellite data for the 2017 wildfire in British Columbia was examined as an example for the northern hemisphere. For this one, it was concluded that no connections between the Canadian wildfire and ozone destruction produced by ozone depleting substances could be found in the data. This is a very positive finding for nature’s health since it means that at least one of the biggest wildfires in recent history did not harm the ozone layer. The reason might be that the fire was not big enough and, therefore, not enough smoke reached the stratosphere to cause the production of ozone depleting substances. However, because of global climate change and with that increasing temperatures, big wildfires are expected to occur more often, and thus, we should better understand their effects on our ozone layer.

• author: Grüner, Christopher
• supervisor: Johan Friberg; Carl Svenhag
• organization: Department of Physics; Nuclear physics
• course: FYSM33 20231
• year: 2023
• type: H2 - Master's Degree (Two Years)
• subject: Physics and Astronomy
• language: English
• id: 9112973
• date added to LUP: 2023-04-17 11:17:29
• date last changed: 2023-04-17 11:17:29