Surface ozone exceedances in Melbourne, Australia are shown to be under NOx control, as demonstrated using formaldehyde:NO2 and glyoxal:formaldehyde ratios

Ryan, Robert G.; Rhodes, Steve; Tully, Matthew B.; Schofield, Robyn

doi:10.1016/j.scitotenv.2020.141460

Cited by 29 publications

(17 citation statements)

References 43 publications

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“…Moreover, the ratio has an altitude dependence (e.g., Jin et al, 2017;Schroeder et al, 2017). While seasonal variations and trends in the columnar HCHO/NO 2 ratio (i.e., based on satellite observations) generally match the ratio computed with in situ observations, magnitudes are often different due to different vertical distributions of HCHO and NO 2 (Ryan et al, 2020). Therefore, although O 3 sensitivity derived from satellite column data can differ somewhat from that based on in situ observations (Schroeder et al, 2017), it nonetheless provides useful information and has been extensively studied in relation to COVID-19 (e.g., Ghahremanloo et al, 2021, among others).…”

Section: Trends and Seasonal Changesmentioning

confidence: 95%

“…The HCHO-to-NO 2 concentration ratio is an indicator of near-surface O 3 sensitivity (e.g., Martin et al, 2004). Traditionally, the ozone production regime is considered to be VOC-limited when this ratio is lower than 1 and NO x -limited when it is higher than 2, while ozone is expected to be in the transition regime when the values are in the range 1-2 (Duncan et al, 2010;Ryan et al, 2020). Although several studies used this ratio to infer O 3 sensitivity to NO x and VOCs by using observations from satellite and ground-based instruments (Duncan et al, 2010;Jin et al, 2017;Schroeder et al, 2017;Irie et al, 2021), some limitations still exist.…”

Section: Trends and Seasonal Changesmentioning

confidence: 99%

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Peculiar COVID-19 effects in the Greater Tokyo Area revealed by spatiotemporal variabilities of tropospheric gases and light-absorbing aerosols

et al. 2022

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Abstract. This study investigated the spatiotemporal variabilities in nitrogen dioxide (NO2), formaldehyde (HCHO), ozone (O3), and light-absorbing aerosols within the Greater Tokyo Area, Japan, which is the most populous metropolitan area in the world. The analysis is based on total tropospheric column, partial tropospheric column (within the boundary layer), and in situ observations retrieved from multiple platforms as well as additional information obtained from reanalysis and box model simulations. This study mainly covers the 2013–2020 period, focusing on 2020 when air quality was influenced by the coronavirus 2019 (COVID-19) pandemic. Although total and partial tropospheric NO2 columns were reduced by an average of about 10 % in 2020, reductions exceeding 40 % occurred in some areas during the pandemic state of emergency. Light-absorbing aerosol levels within the boundary layer were also reduced for most of 2020, while smaller fluctuations in HCHO and O3 were observed. The significantly enhanced degree of weekly cycling of NO2, HCHO, and light-absorbing aerosol found in urban areas during 2020 suggests that, in contrast to other countries, mobility in Japan also dropped on weekends. We conclude that, despite the lack of strict mobility restrictions in Japan, widespread adherence to recommendations designed to limit the COVID-19 spread resulted in unique air quality improvements.

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Section: Trends and Seasonal Changesmentioning

confidence: 95%

Section: Trends and Seasonal Changesmentioning

confidence: 99%

Peculiar COVID-19 effects in the Greater Tokyo Area revealed by spatiotemporal variabilities of tropospheric gases and light-absorbing aerosols

et al. 2022

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“…Such datasets are used in, but are not limited to, (1) air quality assessment and monitoring, (2) evaluation of chemistry transport models (CTMS), and (3) validation of satellite data retrievals. Several studies have used MAX-DOAS datasets to validate tropospheric columns retrieved from satellite observations, including NO 2 and HCHO (Irie et al, 2008b;Ma et al, 2013;Chan et al, 2020;Ryan et al, 2020). However, limited MAX-DOAS datasets have been used to evaluate global CTMs.…”

Section: Introductionmentioning

confidence: 99%

Multi-axis differential optical absorption spectroscopy (MAX-DOAS) observations of formaldehyde and nitrogen dioxide at three sites in Asia and comparison with the global chemistry transport model CHASER

et al. 2022

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Abstract. Formaldehyde (HCHO) and nitrogen dioxide (NO2) concentrations and profiles were retrieved from ground-based multi-axis differential optical absorption spectroscopy (MAX-DOAS) observations during January 2017–December 2018 at three sites in Asia: (1) Phimai (15.18∘ N, 102.5∘ E), Thailand; (2) Pantnagar (29∘ N, 78.90∘ E) in the Indo-Gangetic Plain (IGP), India; and (3) Chiba (35.62∘ N, 140.10∘ E), Japan. Retrievals were performed using the Japanese MAX-DOAS profile retrieval algorithm ver. 2 (JM2). The observations were used to evaluate the NO2 and HCHO partial columns and profiles (0–4 km) simulated using the global chemistry transport model (CTM) CHASER (Chemical Atmospheric General Circulation Model for Study of Atmospheric Environment and Radiative Forcing). The NO2 and HCHO concentrations at all three sites showed consistent seasonal variation throughout the investigated period. Biomass burning affected the HCHO and NO2 variations at Phimai during the dry season and at Pantnagar during spring (March–May) and post-monsoon (September–November). Results found for the HCHO-to-NO2 ratio (RFN), an indicator of high ozone sensitivity, indicate that the transition region (i.e., 1 < RFN < 2) changes regionally, echoing the recent finding for RFN effectiveness. Moreover, reasonable estimates of transition regions can be derived, accounting for the NO2–HCHO chemical feedback. The model was evaluated against global NO2 and HCHO columns data retrieved from Ozone Monitoring Instrument (OMI) observations before comparison with ground-based datasets. Despite underestimation, the model well simulated the satellite-observed global spatial distribution of NO2 and HCHO, with respective spatial correlations (r) of 0.73 and 0.74. CHASER demonstrated good performance, reproducing the MAX-DOAS-retrieved HCHO and NO2 abundances at Phimai, mainly above 500 m from the surface. Model results agree with the measured variations within the 1-sigma (1σ) standard deviation of the observations. Simulations at higher resolution improved the modeled NO2 estimates for Chiba, reducing the mean bias error (MBE) for the 0–2 km height by 35 %, but resolution-based improvements were limited to surface layers. Sensitivity studies show that at Phimai, pyrogenic emissions contribute up to 50 % and 35 % to HCHO and NO2 concentrations, respectively.

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“…When BVOCs were removed from their model, ozone exceedances on very hot days disappeared, demonstrating the dominant role of BVOC emissions from Eucalyptus trees (versus anthropogenic VOCs) in ozone formation in Sydney. In Melbourne, Ryan et al (2020) confirmed that ozone is controlled by NO x levels in all seasons, and therefore policy actions to limit NO x will result in reduced ozone. This is of particular importance for mitigating future summertime ozone exceedances, as more extreme summer temperatures are expected due to climate change.…”

Section: Air Quality In Australasiamentioning

confidence: 95%

Key challenges for tropospheric chemistry in the Southern Hemisphere

Paton-Walsh

Emmerson

Garland

et al. 2022

Elementa: Science of the Anthropocene

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This commentary paper from the recently formed International Global Atmospheric Chemistry (IGAC) Southern Hemisphere Working Group outlines key issues in atmospheric composition research that particularly impact the Southern Hemisphere. In this article, we present a broad overview of many of the challenges for understanding atmospheric chemistry in the Southern Hemisphere, before focusing in on the most significant factors that differentiate it from the Northern Hemisphere. We present sections on the importance of biogenic emissions and fires in the Southern Hemisphere, showing that these emissions often dominate over anthropogenic emissions in many regions. We then describe how these and other factors influence air quality in different parts of the Southern Hemisphere. Finally, we describe the key role of the Southern Ocean in influencing atmospheric chemistry and conclude with a description of the aims and scope of the newly formed IGAC Southern Hemisphere Working Group.

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Surface ozone exceedances in Melbourne, Australia are shown to be under NOx control, as demonstrated using formaldehyde:NO2 and glyoxal:formaldehyde ratios

Cited by 29 publications

References 43 publications

Peculiar COVID-19 effects in the Greater Tokyo Area revealed by spatiotemporal variabilities of tropospheric gases and light-absorbing aerosols

Peculiar COVID-19 effects in the Greater Tokyo Area revealed by spatiotemporal variabilities of tropospheric gases and light-absorbing aerosols

Multi-axis differential optical absorption spectroscopy (MAX-DOAS) observations of formaldehyde and nitrogen dioxide at three sites in Asia and comparison with the global chemistry transport model CHASER

Key challenges for tropospheric chemistry in the Southern Hemisphere

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