Sources and Trends of CO, O<sub>3</sub>, and Aerosols at the Mount Bachelor Observatory (2004–2022)
Understanding baseline O<sub>3</sub> is important as it defines the fraction of O<sub>3</sub> coming from global sources and not subject to local control. We report the occurrence and sources of high baseline ozone days, defined as a day where the daily maximum 8 h average (M...
Saved in:
| Main Authors: | , , |
|---|---|
| Format: | Article |
| Language: | English |
| Published: |
MDPI AG
2025-01-01
|
| Series: | Atmosphere |
| Subjects: | |
| Online Access: | https://www.mdpi.com/2073-4433/16/1/85 |
| Tags: |
Add Tag
No Tags, Be the first to tag this record!
|
| _version_ | 1832589108190380032 |
|---|---|
| author | Noah Bernays Jakob Johnson Daniel Jaffe |
| author_facet | Noah Bernays Jakob Johnson Daniel Jaffe |
| author_sort | Noah Bernays |
| collection | DOAJ |
| description | Understanding baseline O<sub>3</sub> is important as it defines the fraction of O<sub>3</sub> coming from global sources and not subject to local control. We report the occurrence and sources of high baseline ozone days, defined as a day where the daily maximum 8 h average (MDA8) exceeds 70 ppb, as observed at the Mount Bachelor Observatory (MBO, 2.8 km asl) in Central Oregon from 2004 to 2022. We used various indicators and enhancement ratios to categorize each high-O<sub>3</sub> day: carbon monoxide (CO), aerosol scattering, the water vapor mixing ratio (WV), the aerosol scattering-to-CO ratio, backward trajectories, and the NOAA Hazard Mapping System Fire and Smoke maps. Using these, we identified four causes of high-O<sub>3</sub> days at the MBO: Upper Troposphere/Lower Stratosphere intrusions (UTLS), Asian long-range transport (ALRT), a mixed UTLS/ALRT category, and events enhanced by wildfire emissions. Wildfire sources were further divided into two categories: smoke transported in the boundary layer to the MBO and smoke transported in the free troposphere from more distant fires. Over the 19-year period, 167 high-ozone days were identified, with an increasing fraction due to contributions from wildfire emissions and a decreasing fraction of ALRT events. We further evaluated trends in the O<sub>3</sub> and CO data distributions by season. For O<sub>3</sub>, we found an overall increase in the mean and median values of 2.2 and 1.5 ppb, respectively, from the earliest part of the record (2004–2013) compared to the later part (2014–2022), but no significant linear trends in any season. For CO, we found a significant positive trend in the summer 95th percentiles, associated with increasing fires in the Western U.S., and a strong negative trend in the springtime values at all percentiles (1.6% yr<sup>−1</sup> for 50th percentile). This decline was likely associated with decreasing emissions from East Asia. Overall, our findings are consistent with the positive trend in wildfires in the Western United States and the efforts in Asia to decrease emissions. This work demonstrates the changing influence of these two source categories on global background O<sub>3</sub> and CO. |
| format | Article |
| id | doaj-art-409a25dc24e54a13bd4f1f7b6c50a727 |
| institution | Kabale University |
| issn | 2073-4433 |
| language | English |
| publishDate | 2025-01-01 |
| publisher | MDPI AG |
| record_format | Article |
| series | Atmosphere |
| spelling | doaj-art-409a25dc24e54a13bd4f1f7b6c50a7272025-01-24T13:21:58ZengMDPI AGAtmosphere2073-44332025-01-011618510.3390/atmos16010085Sources and Trends of CO, O<sub>3</sub>, and Aerosols at the Mount Bachelor Observatory (2004–2022)Noah Bernays0Jakob Johnson1Daniel Jaffe2School of Science, Technology, Engineering and Mathematics, University of Washington Bothell, 18115 Campus Way NE, Bothell, WA 98011, USASchool of Science, Technology, Engineering and Mathematics, University of Washington Bothell, 18115 Campus Way NE, Bothell, WA 98011, USASchool of Science, Technology, Engineering and Mathematics, University of Washington Bothell, 18115 Campus Way NE, Bothell, WA 98011, USAUnderstanding baseline O<sub>3</sub> is important as it defines the fraction of O<sub>3</sub> coming from global sources and not subject to local control. We report the occurrence and sources of high baseline ozone days, defined as a day where the daily maximum 8 h average (MDA8) exceeds 70 ppb, as observed at the Mount Bachelor Observatory (MBO, 2.8 km asl) in Central Oregon from 2004 to 2022. We used various indicators and enhancement ratios to categorize each high-O<sub>3</sub> day: carbon monoxide (CO), aerosol scattering, the water vapor mixing ratio (WV), the aerosol scattering-to-CO ratio, backward trajectories, and the NOAA Hazard Mapping System Fire and Smoke maps. Using these, we identified four causes of high-O<sub>3</sub> days at the MBO: Upper Troposphere/Lower Stratosphere intrusions (UTLS), Asian long-range transport (ALRT), a mixed UTLS/ALRT category, and events enhanced by wildfire emissions. Wildfire sources were further divided into two categories: smoke transported in the boundary layer to the MBO and smoke transported in the free troposphere from more distant fires. Over the 19-year period, 167 high-ozone days were identified, with an increasing fraction due to contributions from wildfire emissions and a decreasing fraction of ALRT events. We further evaluated trends in the O<sub>3</sub> and CO data distributions by season. For O<sub>3</sub>, we found an overall increase in the mean and median values of 2.2 and 1.5 ppb, respectively, from the earliest part of the record (2004–2013) compared to the later part (2014–2022), but no significant linear trends in any season. For CO, we found a significant positive trend in the summer 95th percentiles, associated with increasing fires in the Western U.S., and a strong negative trend in the springtime values at all percentiles (1.6% yr<sup>−1</sup> for 50th percentile). This decline was likely associated with decreasing emissions from East Asia. Overall, our findings are consistent with the positive trend in wildfires in the Western United States and the efforts in Asia to decrease emissions. This work demonstrates the changing influence of these two source categories on global background O<sub>3</sub> and CO.https://www.mdpi.com/2073-4433/16/1/85ozonebaseline ozoneMt. BachelorPacific Northwesthigh elevation |
| spellingShingle | Noah Bernays Jakob Johnson Daniel Jaffe Sources and Trends of CO, O<sub>3</sub>, and Aerosols at the Mount Bachelor Observatory (2004–2022) Atmosphere ozone baseline ozone Mt. Bachelor Pacific Northwest high elevation |
| title | Sources and Trends of CO, O<sub>3</sub>, and Aerosols at the Mount Bachelor Observatory (2004–2022) |
| title_full | Sources and Trends of CO, O<sub>3</sub>, and Aerosols at the Mount Bachelor Observatory (2004–2022) |
| title_fullStr | Sources and Trends of CO, O<sub>3</sub>, and Aerosols at the Mount Bachelor Observatory (2004–2022) |
| title_full_unstemmed | Sources and Trends of CO, O<sub>3</sub>, and Aerosols at the Mount Bachelor Observatory (2004–2022) |
| title_short | Sources and Trends of CO, O<sub>3</sub>, and Aerosols at the Mount Bachelor Observatory (2004–2022) |
| title_sort | sources and trends of co o sub 3 sub and aerosols at the mount bachelor observatory 2004 2022 |
| topic | ozone baseline ozone Mt. Bachelor Pacific Northwest high elevation |
| url | https://www.mdpi.com/2073-4433/16/1/85 |
| work_keys_str_mv | AT noahbernays sourcesandtrendsofcoosub3subandaerosolsatthemountbachelorobservatory20042022 AT jakobjohnson sourcesandtrendsofcoosub3subandaerosolsatthemountbachelorobservatory20042022 AT danieljaffe sourcesandtrendsofcoosub3subandaerosolsatthemountbachelorobservatory20042022 |