## 3 Methods  
### Data  
Daily ozone and aerosol measurements observed by the ozone mapping and profiler suite (OMPS) aboard the Suomi National Polar-orbiting Partnership (Suomi NPP) satellite [34] were retrieved using the OPeNDAP framework. OPeNDAP stands for _Open-source Project for a Network Data Access Protocol_. It provides a way to share data more easily across the world. Documentation for how to use OPeNDAP can be accessed via the following  
Figure 3: Pathway for smoke particles from intense bushfires to enter the stratosphere and for those same particles to, in turn, lead to ozone depletion. Source: [26]. link ([[https://www.opendap.org/support/user-documentation](https://www.opendap.org/support/user-documentation)]([https://www.opendap.org/support/user-documentation](https://www.opendap.org/support/user-documentation)), accessed on 4 May 2022). As a satellite passes along a polar orbit it traces out a swath, with the width depending on the field of view of the measurement device. An insufficient field of view results in coverage gaps between each swath where no data are measured. The measurements accumulated along the swaths are converted into a daily gridded map product: data that have been processed into a standard format and are accessible to a user. This is conducted using a gridding algorithm [35]. The dataset used contains measurements starting on 25 January 2012, while data for it are still being added. The spatial coverage is global, but is incomplete where coverage gaps occur, particularly for UV Aerosol index measurements because of a narrower field of view of the instrument. The ozone values are measured in Dobson units (DU), but the UV Aerosol index has no units attached. Importantly, Dobson units (DU) are a measure of the amount of a gas, usually ozone, in a vertical column descending through the atmosphere; in the case of ozone it is called _total column zone_. [PERSON] 2011 [36] modeled the effect of bushfire emission on the near-surface concentrations of ozone. In our study, we focus only on the effect on total column ozone (i.e., ozone within a column of air from the Earth's surface to the top of the atmosphere). Figure 4, taken from [[https://csl.noaa.gov/assessments/ozone/2018/twentyquestions/](https://csl.noaa.gov/assessments/ozone/2018/twentyquestions/)]([https://csl.noaa.gov/assessments/ozone/2018/twentyquestions/](https://csl.noaa.gov/assessments/ozone/2018/twentyquestions/)), accessed on 30 June 2023, provides a schematic of ozone levels at different heights in the atmosphere. This particular ozone level diagram indicates how ozone varies with height in the tropics. Notice that predominantly ozone is concentrated in the stratosphere, with its distribution peaking at around 23 km. The unit DU is defined per unit of area--the area that is occupied by the horizontal cross-section of the total column--and is the thickness (in units of 10 \(\upmu\)m) of the layer that would be formed if the total column were subjected to standard pressure and temperature. For example, the average for a given total column of ozone is about 300 DU, equivalent to a layer with a thickness of 300 [10 \(\upmu\)m], or 3 mm. Throughout this study, any mention of  
Figure 4: Schematic of ozone levels ozone within a column of air from the Earth’s surface (0 km) to the top of the atmosphere (>35 km). Taken from [[https://csl.noaa.gov/assessments/ozone/2018/twentyquestions/](https://csl.noaa.gov/assessments/ozone/2018/twentyquestions/)]([https://csl.noaa.gov/assessments/ozone/2018/twentyquestions/](https://csl.noaa.gov/assessments/ozone/2018/twentyquestions/)), accessed on 30 June 2023.  
ozone value means the total column ozone, unless explicitly specified. Ozone value data are loaded into the R programming environment using the Terra package ([[https://github.com/rspatial/terra](https://github.com/rspatial/terra)]([https://github.com/rspatial/terra](https://github.com/rspatial/terra)), accessed on 22 May 2022).