AS3.9

Atmospheric composition variability and trends

The session focuses on the variability of the tropospheric and stratospheric chemical composition on the timescales from diurnal to decadal. It discusses the processes driving this variability and attribution of changes. Special emphasis is put on the scientific value of high-quality long-term measurement data sets and supporting model simulations, though the elements related to emerging data sources, measurement campaign that addresses specific processes and long-term projections of the atmospheric chemical composition are also welcome in the session. The presentations that address policy-relevant datasets on atmospheric composition are cordially invited.
Researchers are invited to present novel scientific results from mid- and long-term observational time series from various programmes and networks such as the Global Atmosphere Watch (GAW) Programme, European Monitoring, and Evaluation Programme (EMEP), Network for the Detection of Atmospheric Composition Change (NDACC), Southern Hemisphere Additional Ozonesondes (SHADOZ), Advanced Global Atmospheric Gases Experiment (AGAGE), National Oceanic and Atmospheric Administration (NOAA), regular airborne (e.g. CARIBIC, IAGOS, CONTRAIL) and other campaigns as well as satellite data and model simulations. Data relevant to tropospheric and stratospheric composition, in particular, related to ozone depletion, climate change, and air quality as well as firn data on past atmospheric composition are welcome. We welcome contributions from multi-year modeling studies and inter-comparison exercises that address past and future tropospheric or stratospheric composition changes, carried out in the framework of international projects and initiatives.

Convener: Oksana Tarasova | Co-conveners: Pedro Jimenez-Guerrero, Andrea Pozzer, Euan Nisbet
Presentations
| Thu, 26 May, 08:30–11:44 (CEST), 13:20–13:55 (CEST)
 
Room M1

Presentations: Thu, 26 May | Room M1

Chairpersons: Euan Nisbet, Stoyka Netcheva
08:30–08:37
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EGU22-4997
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ECS
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Virtual presentation
Gunadhar Barik

Aerosols play a significant role in Indian seasonal variation. In this study, inorganic chemistry of the atmospheric aerosols including the gaseous pollutants, such as SO2, NO2, and NH3, were analyzed during seasonal variation (pre-monsoon, monsoon, post-monsoon, and winter seasons) in a peri-urban location in the lower Gangetic basin (LGP). The aerosol inorganic chemistry was analyzed for the surface concentration of NO3, SO4, and NH4. The aerosol samples including gaseous compounds were collected using a high-volume sampler (HVS) (passive), and through dry deposition (active) on to a petri dish. The samples were collected from March 2019 to February 2020, with a sampling frequency of twice a week. The average dust flux was found around 9.85 and 15.49 ug cm-2h-1 in pre-monsoon, 5.298 and 5.432 ug cm-2h-1 in monsoon, 12.04 and 16.15 ug cm-2h-1 in post-monsoon and 12.28 and 16.84 ug cm-2h-1 in winter season through active and passive methods, correspondingly. The estimated SO2, NO2, and NH3 were 14.32, 9.22, and 23.49 ug m-3 in pre-monsoon, 18.335, 8.277, and 22.855 ug m-3 in monsoon, 29.83, 5.28 and 24.85 ug m-3 in post-monsoon and 22.56, 10.68 and 22.46 ug m-3 in winter season respectively. The estimated SO4, NO3 and NH4 were 0.07, 0.04 and 0.1 µg cm-2 in pre-monsoon, 0.1, 0.04, and 0.06 µg cm-2 in monsoon, 0.09, 0.04, and 0.07 µg cm-2 in post-monsoon and 0.08, 0.02 and 0.07 in winter season, respectively. The correlations of the gaseous components with components derived from the aerosol surface remain weak, however positive in most of the seasons, suggesting no significant uptake of the gaseous pollutant by the aerosols. The linear modeling of these chemical species with the weather parameters (temperature, RH, and wind speed) including AOD, derived from MODIS, showed dynamic relationships implying a significant modification of atmospheric properties moderated by the weather parameters. The HYSPLIT model of 3 days’ back trajectory and PSCF model indicated during pre-monsoon, post-monsoon, and winter seasons 60-80% cluster and aerosol were originated from the IGP, east-coast, and eastern part of India, however during monsoons season 70-80% cluster and aerosol were originated from the Arabian sea and the Bay of Bengal, suggesting the nearby dominated local sources of these aerosol components.

How to cite: Barik, G.: Analysis of seasonal inorganic chemistry of aerosols with source attribution in a peri-urban landscape in lower Gangetic basin, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-4997, https://doi.org/10.5194/egusphere-egu22-4997, 2022.

08:37–08:44
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EGU22-6026
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ECS
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Virtual presentation
Jakob Boyd Pernov, Peter Tunved, Sangeeta Sharma, Eija Asmi, Niku Kivekäs, Julia Schmale, Johan Ström, Hans-Christen Hansson, Henrik Skov, and Andreas Massling

Introduction

The Arctic region is particularly sensitive to global climate change, experiencing warming at twice the rate of the global average. Changes within and outside of the Arctic (e.g., meteorology, atmospheric transport, and precipitation patterns) can have consequences for the sources and sinks of aerosols. Atmospheric aerosols can alter the planetary radiation balance directly through scattering and absorption and indirectly through modification of cloud properties. Understanding the direction and magnitude of recent changes in the Arctic aerosol population is key to elucidating the implications for the changing Arctic, although this remains a scientific challenge. Here we report a Pan-Arctic view of recent trends for aerosol particle number concentrations in different size fractions.

 

Measurement Site & Methods

Measurements were obtained from different stations around the Arctic including Villum Research Station (Villum, 81°36’ N, 16°39’ W, 24 m a.s.l) in northeastern Greenland, Alert (81°28’ N, 62°30’ W, 210 m a.s.l.) in the Canadian Archipelago, Zeppelin Observatory (78°56’ N, 11°53’ E, 474 m a.s.l.) on Svalbard, Pallas (67°58’N, 24°07’ E, 560 m a.s.l.) in northern Finland, and Tiksi (71°36’ N, 128°53’E, 1 m a.s.l.) in the Siberian Arctic.

Particle number size distributions (PNSD) were measured using a Scanning Mobility Particle Sizer (SMPS) at Villum and Alert, and a Differential Mobility Particle Sizer (DMPS) at Zeppelin, Pallas, and Tiksi. Measurements were collected from 2010 to 2018 at all sites except for Zeppelin (2011 to 2019). Number concentrations were calculated by integrating the PNSD for three size fractions: Nucleation (10-35 nm), Aitken (35-80 nm), and Accumulation (80-300 nm). Nucleation number concentrations were unavailable for Zeppelin.

The trends in the number concentration for these size fractions were identified and quantified using the Mann-Kendal test and Theil Sen slope on the 90th % confidence interval via the 3PW algorithm, using the daily median as temporal aggregation and meteorological seasons as temporal segmentation. Only statistically significant trends are discussed.

 

Results

Although the sites Villum, Alert, and Zeppelin are all located in the High Arctic (> 75° N) and relatively close to one another, there are differences between the direction and magnitude of trends for the size fractions. For example, at Villum, increasing trends are observed for the Nucleation fraction during spring and summer. Interestingly, at Alert, decreasing trends are observed for the Accumulation fraction during spring and autumn. At Zeppelin, no significant trends were observed for any fraction during any season.

           Similar to the High Arctic sites, for the continental sites, Tiksi and Pallas, no uniform picture for the direction and magnitude of trends in the size fractions is observed. At Tiksi, decreasing trends for both the Aitken and Accumulation fractions are detected during summer and autumn. While at Pallas, no significant trends were observed during any season.

           This work offers insight into the climatic implications (i.e., radiative balance and cloud properties) for a future Arctic climate by monitoring changes of aerosol concentrations in optically and cloud-relevant sizes. Future work will investigate the causes of these trends.

How to cite: Pernov, J. B., Tunved, P., Sharma, S., Asmi, E., Kivekäs, N., Schmale, J., Ström, J., Hansson, H.-C., Skov, H., and Massling, A.: Pan-Arctic trends of aerosol particle number concentrations in different size fractions, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-6026, https://doi.org/10.5194/egusphere-egu22-6026, 2022.

08:44–08:51
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EGU22-11254
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Virtual presentation
Mathew Sebastian, Sobhan Kumar Kompalli, Anil Kumar, Sandhya Jose, S. Suresh Babu, Govindan Pandithurai, Sachchidanand Singh, Rakesh K. Hooda, Vijay K. Soni, Jeffrey R. Pierce, Ville Vakkari, Eija Asmi, Daniel M. Westervelt, Antii-P Hyvarinen, and Vijay P. Kanawade

Particle number size distribution has critical importance in characterizing the number, size, surface area, volume, and evolution of aerosols in the atmosphere. Atmospheric new particle formation (NPF) is one the largest source of aerosol numbers to the terrestrial atmosphere and greatly impact the evolution of particle number size distribution. Here, we analyzed at least one year of asynchronous measurements of particle number size distributions from six different locations in India. We found that NPF frequently occurs at all locations in the pre-monsoon season (March through May) and is the least common in the post-monsoon season (October-November).   Considering all sites (mountain background, mountain semi-rural, coastal semi-urban and urban), the particle formation rate of lowest detectable size (JLDS) varied by more than an order of magnitude (0.01 - 0.6 cm-3 s-1) and the growth rate between the lowest detectable size and 25 nm (GRLDS-25nm) by about three orders of magnitude (0.2 - 17.2 nm h-1). The site-specific JLDS and GRLDS-25nm are positively correlated, indicating their co-dependence on gas-phase production rates of low-volatility vapors, driven by the source and atmospheric conditions. Our results also showed that NPF events significantly modulate the shape of particle number size distributions, particularly in the pre-monsoon season. The NPF-associated CCN concentrations were higher in urban locations than the mountain background sites. Although using asynchronous measurements, our results implicate the process-level characterization of particle number size distribution.

How to cite: Sebastian, M., Kumar Kompalli, S., Kumar, A., Jose, S., Babu, S. S., Pandithurai, G., Singh, S., K. Hooda, R., K. Soni, V., R. Pierce, J., Vakkari, V., Asmi, E., M. Westervelt, D., Hyvarinen, A.-P., and P. Kanawade, V.: Characterization of particle number size distributions and new particle formation in different Indian locations, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-11254, https://doi.org/10.5194/egusphere-egu22-11254, 2022.

08:51–08:58
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EGU22-29
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Presentation form not yet defined
Hygroscopicity of organic aerosols linked to formation mechanisms 
(withdrawn)
Jieyao Liu, Fang Zhang, Weiqi Xu, Yele Sun, Lu Chen, Shangze Li, Jingye Ren, Bo Hu, Hao Wu, and Renyi Zhang
08:58–09:05
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EGU22-537
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ECS
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Virtual presentation
Sandeep Devaliya, Prem Maheshwarkar, Ankur Bhardwaj, Diksha Haswani, Deeksha Shukla, and Ramya Sunder Raman

Modern-Era Retrospective analysis for Research and Applications (MERRA-2) generated  PM2.5  concentrations are widely used to understand the spatio-temporal variability of PM2.5 across the globe. Only PM2.5 data from black carbon, organic carbon, sulphate, sea-salt, and dust are provided by MERRA-2. However, previous studies validated MERRA-2 PM2.5 concentrations obtained by combining all five species data against in-situ ​total PM2.5 concentrations. To the best of our knowledge, this is the first study over India to validate MERRA-2 species wise PM2.5 concentrations utilizing in-situ surface measurements made over a site at Bhopal (23.285° N, 22.277° E). Bhopal is one of the eleven COALESCE (Carbonaceous Aerosol Emissions, Source Apportionment and Climate Impacts) network regionally representative sites in India. 24 hour integrated filter-based samples (N = 165) collected during 2019, using the MetOne SASS® speciation sampler were used to measure mass and aerosol species concentrations by a variety of analyses. Our results show that the MERRA-2 well captures the aerosol species data at Bhopal. However, MERRA-2 underestimated the annual mean in-situ concentration of organic carbon, black carbon, and sulphate by 1.9 µg m -3 (~22 %), 1.3 µg m -3 (~47 %) and 0.9 µg m -3 (~11 %), respectively and overestimated the sea salt and dust components by 0.75 µg m -3 (~95 %) and 8.5 µg m -3 (~153 %), respectively.  It is pertinent to note that dust from surface aerosol chemical species measurements was re-constructed using elemental aluminium, silicon, potassium, calcium, titanium, manganese concentrations. Further, the annual mean MERRA-2 PM2.5 mass (reconstructed from its constituent species) underestimated the average in-situ PM2.5 mass by 13.55 µg m -3 (~26.16 %). This underestimation is likely due to aerosol nitrate not being included in the MERRA2 PM2.5 mass and uncertainties in aerosol species concentrations resulting from limitations in the chemical transport model set-up and emissions inventories. This study discusses the possible causes of disagreements between in-situ measurements and MERRA2 products, in addition to estimating the effect of including nitrate in the MERRA2 PM2.5 mass reconstruction.

How to cite: Devaliya, S., Maheshwarkar, P., Bhardwaj, A., Haswani, D., Shukla, D., and Sunder Raman, R.: Evaluation of the MERRA-2 PM2.5 mass and its constituent chemical species concentrations over a COALESCE network site in Bhopal, India , EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-537, https://doi.org/10.5194/egusphere-egu22-537, 2022.

09:05–09:12
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EGU22-1757
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Virtual presentation
Dina Gubanova, Anna Vinogradova, Andrey Skorokhod, and Mikhail Iordanskii

The results of an intensive complex experiment to study the composition and temporal variability of urban aerosol in near-surface air in the center of Moscow include daily data for two years on concentrations of PM10 and PM2.5 particles. In addition, in each season (for 35-40 days), measurements of the total aerosol mass concentration (by gravimetric method) and 65 chemical elements included in its composition are also carried out daily. For winter seasons, it is from January 10 to February 14, 2020 and 2021. Winter is the season with minimal aerosol pollution in Moscow. The total aerosol mass was 20.8 μg/m3 and 32.0 μg/m3 in the 2019-20 and 2020-21 seasons, respectively. Concentrations of all measured components in near-surface air did not exceed the MPC values for residential areas during both winters. However, the ratios of mass concentrations for particles PM2.5, PM10 and larger particles were different in these years. Mass ratios (in %) of aerosols of different sizes (<2.5 μm):(from 2.5 to 10 μm):(>10 μm) were 23:27:50 and 33:8:59 for 2020 and 2021, respectively. According to weather conditions, these two winters in Moscow were very different: the winter of 2019-2020 was abnormally warm with the shortest duration of snow cover for all the years of observations. On the contrary, the next winter of 2020-2021 was close to normal in terms of the main meteorological parameters, although the wind rose was characterized by an increased frequency of winds from the south. Studies have shown the leading role of meteorological conditions (in particular, humidity and air pressure), as well as long-range atmospheric transport in changing the level of aerosol pollution of near-surface air in Moscow. Analysis of the variability of the chemical element concentrations and enrichment factors (relative to the composition of the Earth's crust) identifies elements of predominantly anthropogenic (for example, Cd, Sb, Pb) or terrigenous (Co, Fe, Al, Cr), as well as global (S, P, B, Se, Bi) or local (Ca, Ni, W) origin. The results of winter observations of urban aerosol in Moscow are compared with the spring data of 2020 [1] and 2021.

The work was financially supported of RFBR, grant No. 19-05-50088.

[1] Gubanova, D.P., Vinogradova, A.A., Iordanskii, M.A., Skorokhod A.I. Time Variations in the Composition of Atmospheric Aerosol in Moscow in Spring 2020. , Atmospheric and Oceanic Physics. 2021. V. 57, No. 3. P. 297–309. https://doi.org/10.1134/S0001433821030051

How to cite: Gubanova, D., Vinogradova, A., Skorokhod, A., and Iordanskii, M.: Properties of near-surface aerosol in Moscow during the season of minimal air pollution (two differing winters of 2019-20 and 2020-21), EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-1757, https://doi.org/10.5194/egusphere-egu22-1757, 2022.

09:12–09:19
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EGU22-1878
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Virtual presentation
George-Bogdan Burghelea, Sabina Stefan, Luminita Marmureanu, and Gabriela Iorga

The year 2020 was marked by the start of SARS-COV2 virus pandemic. As globally, in Romania the social, economic and transport activities were also restricted at various levels during the year. There were many restrictions and even blockages of some activities at national level. This has led to mass concentrations of air pollutants considerably lower and the improvement of the air quality. was easily noticed. For present study, three metropolitan areas of Bucharest (population 2,161,347 inhabitants), Brasov (population 289,502 inhabitants) and Iasi (population 376,180 inhabitants) were analysed for the period 01. January 2019- 31. December 2020. These cities often face problems of exceeding the air quality limit values imposed by the European legislation. Bucharest is constantly monitored by eight stations (type: traffic, urban, regional, suburban, industrial), Brasov is monitored by five stations (type: traffic, urban, industrial, suburban, regional) and Iasi is monitored by six stations (type: traffic, urban, industrial, rural, suburban). The air pollution monitoring data are those provided by the National Air Quality Monitoring Network (RNMCA). Using RNMCA observations, a synthetic data base consisting of daily time series of mass concentrations of major traffic pollutants, NO and PM10, was created and analysed for traffic stations and reference stations of each city. Data were analysed statistically over four time intervals: Business as Usual (01.01-15.03), Lockdown (16.03-15.05), Alert status with traffic restrictions (Alert 1) (16.05-15.08) and Alert status with normal traffic (Alert 2) (16.08- 31.12). Information about the inhabitants was taken from the website of the National Institute of Statistics.

The study shows that in 2020 the pollution levels in the Bucharest metropolitan area were considerably lower for the whole year than in 2019, and during the state of emergency (Lockdown) and the state of alert the pollution levels with PM10 were the lowest in the year. The same observations are valid for the metropolitan areas of Brasov and Iasi. With the relaxation of the restrictions and the entry into the fourth time interval (Alert 2), it was observed that the levels have started to increase by the year 2020. After analysing the NO data according to PM10 at the traffic stations in Bucharest, we determined a lower Pearson's coefficient in 2020 compared to 2019.For the other cities the data cannot be concrete because there are no enough data to draw a firm conclusion for the entire year 2019.

Acknowledgements:

GBB was supported by the University of Bucharest, PhD research grant. SS and GI thanks the support from NO Grants 2014-2021, EEA-RO-NO-0423 project, contract no 31/2020.

Ground-based air pollutant data and meteorology by site were extracted from the public available Romanian National Air Quality Database, www.calitateaer.ro.

Data on the number of inhabitants were extracted from the database of the National Institute of Statistics, www.insse.ro

 

How to cite: Burghelea, G.-B., Stefan, S., Marmureanu, L., and Iorga, G.: Variations in PM10 particle matter levels in three urban areas in Romania-comparative study 2020-2019, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-1878, https://doi.org/10.5194/egusphere-egu22-1878, 2022.

09:19–09:26
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EGU22-6890
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ECS
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Virtual presentation
Yao Yao and zi qi He

Studying the changes of PM2.5 and PM10 in the Yangtze River Economic Belt will help promote the comprehensive management of regional air pollution and promote the ecological environment protection and high-quality economic development of the Yangtze River Economic Belt. This paper selects monthly observation data of six pollutants from 126 cities in the Yangtze River Economic Belt from 2015 to 2020, and applies Mann-Kendall mutation test, Pearson correlation coefficient analysis, spatial autocorrelation analysis and spatial regression analysis to study PM2.5 and PM10 temporal and spatial distribution, evolution characteristic and driving factors, and applies the HYSPLIT backward trajectory analysis model to study the potential impact of long-distance air transport and atmospheric boundary layer conditions on the diffusion and transmission of PM2.5 and PM10 pollution sources in the Yangtze River Economic Belt. The annual average concentrations of PM2.5 and PM10 in the Yangtze River Economic Belt significantly decreased year by year, with obvious seasonal trend of high concentration in winter and low concentration in summer. There is a significant positive spatial correlation relationship, and the spatial accumulation is obvious. In addition, there is a significant positive correlation and homology with other gaseous pollutants. The air mass retrospective direction and atmospheric boundary layer conditions of the upper, middle and lower Yangtze River urban agglomerations have different effects on PM2.5 and PM10. The regional GDP, the proportion of the secondary industry, the population density and the green coverage rate in the built-up areas all affected positively the local PM2.5 and PM10 concentrations. Overall, regional cooperating depollution, synergetic reduction of various air pollutants and transformation of economic development patterns can fundamentally solve the problems of PM2.5 and PM10 pollution in the Yangtze River Economic Belt.

How to cite: Yao, Y. and He, Z. Q.: Variation Characteristics of PM2.5 and PM10 Concentration and its Driving Factors in the Yangtze River Economic Belt, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-6890, https://doi.org/10.5194/egusphere-egu22-6890, 2022.

09:26–09:33
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EGU22-13523
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Presentation form not yet defined
Susan Kizer, Marilee Roell, David Flittner, Robert Damadeo, Kevin Leavor, Carrie Roller, Dale Hurst, Emrys Hall, Allen Jordan, Patrick Cullis, Bryan Johnson, and Richard Querel

The Stratospheric Aerosol and Gas Experiment III (SAGE III) instrument installed on the International Space Station (ISS) has completed almost half of a decade of data collection and production of science data products. The SAGE III/ISS is a solar and lunar occultation instrument that scans the light from the Sun and Moon through the limb of the Earth’s atmosphere to produce vertical profiles of aerosol, ozone, water vapor, and other trace gases. It continues the legacy of previous SAGE instruments dating back to the 1970s to provide data continuity of stratospheric constituents critical for assessing trends in the ozone layer. This presentation shows how SAGE III/ISS aerosol and gas vertical profiles continue to benefit a worldwide database of in situ and satellite data for climate observation.

How to cite: Kizer, S., Roell, M., Flittner, D., Damadeo, R., Leavor, K., Roller, C., Hurst, D., Hall, E., Jordan, A., Cullis, P., Johnson, B., and Querel, R.:  Stratospheric Aerosol and Gas Experiment III on the International Space Station(SAGE III/ISS): Continuing the Legacy of SAGE Data Products, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-13523, https://doi.org/10.5194/egusphere-egu22-13523, 2022.

09:33–09:40
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EGU22-11004
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ECS
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Virtual presentation
Air Quality Measurement Analysis in the Antarctic
(withdrawn)
Ceyhan Kahya and Furkan Ali Kucuk
09:40–09:47
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EGU22-12861
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ECS
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On-site presentation
Morgan Mitchell, Aldona Wiacek, Alan Wilson, and Ian Ashpole

Surface ozone (O3) is an air pollutant that is notoriously difficult to regulate due to its non-linear production that is dependent on emissions of precursor gases (NOx, VOCs) and meteorological conditions. As a small, but expanding, province, containing the largest urban centre in Atlantic Canada, Nova Scotia does not experience concentrations of ozone and its precursors that are characteristic of megacities. However, elevated levels of surface ozone are observed on some days and the chemistry and meteorology behind these events are not well characterized.

This study examines long-term (2000-2021) observational ozone and precursor gas data, as well as associated local emissions inventories, in order to define trends and explain changing ambient levels of ozone in the province. For example, provincial local emissions have been consistently decreasing but ozone concentrations are beginning to rise in recent years and the cause of this rise is investigated.  Although it is known that transboundary pollution is present on some days, the significance of this transported pollution to annual trends was unknown prior to this research.

We introduce and apply a spatial correlation algorithm as a novel method to diagnose transported pollution events that cause high ozone across the province and are able to estimate the proportion of transported pollution in the province over the study period. We find transported pollution to account for 45-63% of the elevated ozone days. We then identify source regions of this transported pollution as well as changes in source regions over time based on results from HYSPLIT model runs.  Vertical ozone concentrations obtained from model forecasts are examined during high ozone events in the province to determine the processes that bring pollutants to the surface from above the boundary layer.

Our results clarify the sensitivity of surface ozone levels in Nova Scotia to changing levels of precursor emissions in upstream areas like NE USA, which have seen an increase in recent years following decades-long reductions. This research has significance for policy-makers working to manage risks from air pollution in growing cities subject strong upstream pollution sources under a changing climate.

How to cite: Mitchell, M., Wiacek, A., Wilson, A., and Ashpole, I.: Controls on surface ozone pollution in the province of Nova Scotia, Canada, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-12861, https://doi.org/10.5194/egusphere-egu22-12861, 2022.

09:47–09:54
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EGU22-2068
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Virtual presentation
Carlos Ordóñez, José M. Garrido-Pérez, and Ricardo García-Herrera

Over the last two years non-pharmaceutical intervention measures in the form of social distancing and lockdowns have been applied to reduce the transmission of SARS-CoV-2. While the exact nature and duration of these measures have varied substantially over the European continent, most countries were under strict lockdowns at the beginning of the pandemic, from mid-March to late April 2020. This caused unprecedented falls in industrial activity and vehicle use, two of the main sources of air pollution.

Here we investigate the effects of that lockdown on the near-surface ozone concentrations. For that purpose, we use 1-h daily maximum nitrogen dioxide (NO2) and maximum daily 8-h running average ozone (MDA8 O3) observations at ~1300 background sites of the European Environment Agency's air quality database (AirBase) as well as a meteorological reanalysis.

We find that the lockdown caused a substantial reduction in NO2 concentrations across Europe, while O3 increased over northwestern and central Europe compared to the same period in 2015-2019. In some countries like Germany, O3 concentrations were typical of the summer season. Atmospheric conditions were also anomalously stable, dry and warm over large parts of the continent, which could potentially rise the O3 concentrations. Consequently, to separate the effect of meteorology and emissions, we have built statistical models fed by reanalysis meteorological data and estimated the expected O3 concentrations during that period in the absence of a lockdown. The results indicate that a considerable fraction of the observed O3 changes can be explained by elevated temperatures, low atmospheric humidity and high solar radiation.

While this analysis shows a dominant role of the meteorology during the early-spring lockdown, we will discuss other factors such as changes in chemical regimes (caused mainly by sharper decreases in emissions of nitrogen oxides than those of volatile organic compounds) that may have yielded regional ozone enhancements during the pandemic.

How to cite: Ordóñez, C., Garrido-Pérez, J. M., and García-Herrera, R.: The role of meteorology in the near-surface ozone enhancements over Europe during the COVID-19 lockdown of early spring 2020, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-2068, https://doi.org/10.5194/egusphere-egu22-2068, 2022.

Coffee break
Chairpersons: Stoyka Netcheva, Euan Nisbet
10:20–10:27
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EGU22-2760
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ECS
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Virtual presentation
Douglas Gregg, Kevin Wyche, Mark Nichols, Harley Parfitt, Paul Beckett, Kirsty Smallbone, and Paul Monks

COVID-19 required governments across the globe put into place a range of measures which resulted in many industries suspending operations and most citizens (i.e., non ‘key-workers’) staying in their homes. As such, anthropogenic activity around the globe decreased rapidly, to such an extent that emissions of air pollutants began to decline dramatically, with this period now being referred to as an ‘anthropause’. In the early stages of the pandemic, remote sensing data from satellites indicated that nitrogen dioxide (NO₂) concentrations had fallen by as much as 30% across China and by as much as 50% across areas of central Europe. Early work using in-situ measurements confirmed these findings, with studies from China, Korea, India, the USA and Europe all reporting decreases in ambient NOx concentrations. The UK government advised that the general population should avoid ‘non-essential’ travel and social contact, on 16th March 2020.  Subsequently, on 23rd March 2020, the government announced a UK-wide partial ‘lockdown’, to contain the spread of the virus. 

In this work, we combine findings from the University of Brighton’s Brighton Atmospheric Observatory and the ESA's Sentinel-5P satellite, to investigate changes in tropospheric Nitrogen Dioxide concentrations in the South East of the UK during the COVID-19 pandemic. BAO comprises a climate controlled, clean laboratory and analytical instruments for making detailed, real-time measurements of tropospheric composition, and is situated in a suburban background environment, roughly 5 km from Brighton city centre. 

Maps showing regional daily average NO₂ concentrations as recorded by TROPOMI were created over (a) the period 25/03/2019–22/04/2019 (i.e. the pre-pandemic baseline) and (b) 23/03/2020–20/04/2020 (i.e. post-implementation of lockdown restrictions). TROPOMI measurements were compared to measurements made on the ground using a long-path DOAS (total path length 300m) for the same time periods. The data confirms findings from analysis of in-situ monitor observations made by the Sussex-Air Network and DEFRA Automatic Urban and Rural Network (AURN), extending the reach of the data capture to the entire South East of the UK on a 7 × 7 km resolution scale. In-line with the in-situ monitors, TROPOMI measured a decrease in the concentrations of NO2 across the entire region during the lockdown, with the regional average value falling by 33%, from 4.9 × 10^16 to 3.3 × 10^16 molec m^-2. The largest changes in NO2 were observed in the centre of the region, in the areas surrounding London and at certain coastal locations.  

TROPOMI measured NO2 values across Brighton and Hove during the 2020 lockdown period to be 59% of those measured over roughly the same time period the previous year (with mean values falling from 4.4 × 10^16 to 2.9 × 10^16 molecule m^-2), comparing favourably with DOAS, which recorded NO₂ values that were ~64% of those measured during the previous two years over roughly the same time period.  

The methodology is also extended to London, Birmingham and Manchester, the 1st, 2nd and 6th largest cities within the UK. 

How to cite: Gregg, D., Wyche, K., Nichols, M., Parfitt, H., Beckett, P., Smallbone, K., and Monks, P.: Changes in ambient air quality and atmospheric composition and reactivity in the South East of the UK as a result of the COVID-19 lockdown, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-2760, https://doi.org/10.5194/egusphere-egu22-2760, 2022.

10:27–10:34
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EGU22-4755
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ECS
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Virtual presentation
Natalia Kirillova, Andrey Skorokhod, Vadim Rakitin, and Eugenia Fedorova

Changes in the atmospheric composition in different periods of 2020 in Moscow, associated with the COVID-19 pandemic preventing measures of varying intensity and with corresponding reduction in emissions of pollutants, were investigated. Surface concentrations of nitrogen dioxide NO2, carbon monoxide CO, ozone O3, aerosol fraction PM10 and meteorological parameters in different periods of 2020 are compared with similar data for the previous 5 years. The analysis of ground-based measurements, as well as high-resolution satellite distributions of CO and NO2, indicated that the content of major pollutants and its spatial distribution in the Moscow region were significantly affected by both restrictive measures and abnormal meteorological conditions in 2020. It is possible to obtain quantitative estimates of the contribution of both factors using transport and chemical modeling based on detailed inventory of anthropogenic emissions.

Additionally, some characteristics of atmospheric composition long-term trends in Moscow region are analyzed and discussed.

The study was supported by Russian Science Foundation under grant №21-17-00210.

How to cite: Kirillova, N., Skorokhod, A., Rakitin, V., and Fedorova, E.: The impact of COVID-19 pandemic preventing measures and meteorological conditions on the atmospheric air composition in Moscow in 2020, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-4755, https://doi.org/10.5194/egusphere-egu22-4755, 2022.

10:34–10:41
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EGU22-8430
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ECS
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Virtual presentation
Bianca Meotti and Leonardo Hoinaski

With the rapid emergence of the novel coronavirus disease 2019 (COVID-19), several lockdowns measures have been used to control the spread of the coronavirus around the world. The restrictions imposed by the lockdowns include partial or complete closure of international borders, schools, and nonessential businesses and, in some cases, restricted citizen mobility. Besides the effect on controlling the virus spread, the associated reduction in traffic and industry has revealed an unprecedented impact on global air pollution. Here we evaluate the impact of the lockdowns on CO concentration in Brazil on a national scale. We use data from Modern-Era Retrospective analysis for Research and Applications, Version 2 (MERRA-2) to analyze the low, median, and higher concentrations of CO in March 2020 compared to the same month in the last 20 years (2000-2019). In March, many Brazilian states declared public health emergency imposing several partial to total lockdowns. Our results reveal that the lockdowns did not reduce the lowest concentrations, since the 25th percentile from March 2020 was approximately 15% higher than the same period from 2000-2019. We observe a decrease in the 90th percentile values from March 2020 when compared to March 2000-2019, suggesting that the lockdowns reduced the highest concentrations which are strongly related to health effects. The 90th percentile concentration of CO in March 2020 was smaller in 50% of the pixels, representing up to 140% of reduction. Spatially, we have observed the maximum reduction due to the lockdowns in the southern and southeast coast, as well as in Roraima state. Lockdowns have also affected the median concentration of CO, reducing the concentration by 70% for 32% of the pixels. Our results confirm the positive impact of the lockdowns on the air quality in Brazil, contributing to mounting evidence that lockdowns and restricting vehicular activities would be an effective way to control the air pollution.

How to cite: Meotti, B. and Hoinaski, L.: Impact of lockdowns implementations on CO concentration in Brazil during March 2020, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-8430, https://doi.org/10.5194/egusphere-egu22-8430, 2022.

10:41–10:48
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EGU22-9565
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ECS
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Virtual presentation
Vigneshkumar Balamurugan, Jia Chen, Zhen Qu, Xiao Bi, and Frank N. Keutsch

The COVID-19 lockdown is viewed as a natural experiment that can put our current understanding of the contribution of secondary PM2.5 sources to the test. In ten German metropolitan areas, mean meteorology-accounted for PM2.5 concentrations dropped by 5 % during the 2020 lockdown period (spring) compared to 2019, but meteorology-accounted for NO2 concentrations decreased by 23 % during the same time. Furthermore, meteorology-accounted for SO2 and CO concentrations show no significant differences between the 2020 lockdown period and 2019. The GEOS-Chem model simulation with COVID-19 emission reduction scenario (23 % reduction in NOX emission with unchanged VOC and SO2) supports our findings of only a marginal decrease in PM2.5 and a significant decrease in NO2 levels and reveals that the atmosphere's oxidative capacity is increased in all three important oxidants, OH, O3, and night-time NO3. The night-time increase in O3 is the main cause of increase in night-time NO3 radical. The increase in OH does not compensate for the strong reductions in NO2, whereas the increase in NO3 radical at night roughly balances the effects of the NO2 reduction. As a result, compared to the Business As Usual condition, i.e., no lockdown, day-time PM nitrates are reduced while night-time PM nitrate formation is relatively unaffected. In addition to the above, slightly enhanced sulfate formation and decreased ammonium explain the small reduction in the total PM2.5 during the lockdown period. We also investigated the annual spring high PM2.5 episodes in German metropolitan areas. Satellite measurements show high ammonia (NH3) concentrations in the early spring and summer months, when high PM2.5 episodes are associated with high NH3 concentrations in the spring. We find that high atmospheric ammonia concentrations, combined with low temperature and low boundary layer height, are the most favorable conditions for PM2.5 formation. Based on our findings, we suggest that emission control policies should be more focused on limiting ozone that should also reduce PM2.5. Furthermore, ammonia emissions should be limited in order to control the high PM2.5 episodes in winter and spring.

How to cite: Balamurugan, V., Chen, J., Qu, Z., Bi, X., and Keutsch, F. N.: Reduction in NOX emissions during the COVID-19 lockdown did not result in a comparable reduction in secondary PM levels, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-9565, https://doi.org/10.5194/egusphere-egu22-9565, 2022.

10:48–10:55
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EGU22-9280
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ECS
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Virtual presentation
Simone M. Pieber, Dac-Loc Nguyen, Hendryk Czech, Stephan Henne, Nicolas Bukowiecki, Nhat Anh Nguyen, Brigitte Buchmann, Lukas Emmenegger, and Martin Steinbacher

We present air quality and trace gas observations at the regional Global Atmosphere Watch (GAW) station Pha Din (PDI) in rural Northwestern Vietnam. PDI is located in a sparsely populated area on the top of a hill (1466 m a.s.l.) [1], and frequently receives pollution plumes from large-scale fires on the Indochinese Peninsula [1]. We previously analyzed carbonaceous PM2.5 chemical composition in an intensive campaign conducted during 3 weeks in March-April 2015. The study included measurements of elemental and organic carbon (EC/OC) and more than 50 organic markers, such as sugars, PAHs, fatty acids and nitro-aromatics [2]. For this intensive campaign, we linked trace gas mixing ratios of CO, CO2, CH4 and O3 to a statistical classification of large-scale fires, which was based on organic aerosol composition. We found increased CO and O3 levels during medium and high biomass burning influence during March-April 2015. A backward trajectory analysis confirmed different source regions for the identified periods based on the organic aerosol cluster. The more polluted periods were characterized by trajectories from southwest, with more continental recirculation of the medium cluster, and more westerly advection for the high cluster. Cleaner air masses instead arrived from northeast, i.e., mainland China and Yellow sea during this period.  These findings highlighted that biomass burning in Northern Southeast Asia significantly enhances the regional organic aerosol loading, chemical PM2.5 composition and the trace gases in northwestern Vietnam [2]. For our contribution to EGU22, we extend this analysis to a multi-year period and present continuous trace gas observations of CO2, CH4, CO, and O3 conducted at PDI since 2014. The data are interpreted with atmospheric transport simulations, and add valuable insight on air quality and trace gas mixing ratios in a region of scarce data availability.

REFERENCES: [1] Bukowiecki, N. et al. Effect of Large-scale Biomass Burning on Aerosol Optical Properties at the GAW Regional Station Pha Din, Vietnam. AAQR 19, 1172–1187 (2019). [2] Nguyen, D. L, et al. Carbonaceous aerosol composition in air masses influenced by large-scale biomass burning: a case-study in Northwestern Vietnam. Atmos. Chem. Phys., 21, 8293–8312 (2021) https://doi.org/10.5194/acp-21-8293-2021

FUNDING AND ACKNOWLEDGMENTS:  Capacity Building and Twinning for Climate Observing Systems (CATCOS), GAW Quality Assurance/Science Activity Centre Switzerland (QA/SAC-CH), Swiss National Science Foundation (SNSF) (194390), German Academic Exchange Service (DAAD), Vietnam Academy of Science and Technology (VAST).

How to cite: Pieber, S. M., Nguyen, D.-L., Czech, H., Henne, S., Bukowiecki, N., Nguyen, N. A., Buchmann, B., Emmenegger, L., and Steinbacher, M.: Air quality and trace gas observations at the GAW site Pha Din (Vietnam), EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-9280, https://doi.org/10.5194/egusphere-egu22-9280, 2022.

10:55–11:02
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EGU22-11067
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On-site presentation
Christoph Gerbig, Uwe Schultz, Thomas Seifert, Harald Franke, Ralf Stosius, and Philippe Nedelec

Within European Research Infrastructure IAGOS (In-service Aircraft for a Global Observing System) regular observations of atmospheric greenhouse gases have started in 2018 onboard a Lufthansa Airbus A330. The aircraft is based in Frankfurt with service to destinations in central Africa, the Middle East, and North America. During the initial deployment periods, each lasting from several months to more than a year, various lessons have been learned related to the robustness and resilience of the autonomous operation of the IAGOS-core system, its maintenance in the laboratory, as well as the data transmission and regular automated processing of near-real-time (NRT) data with provision to users through the IAGOS data centre. Equipped with a two-standard in-flight calibration system, trace gas measurements could be made fully traceable to WMO calibration scales. The Covid-19 Pandemic had a significant impact on aviation, and thus on the IAGOS operation, but the aircraft carrying the IAGOS GHG equipment was flying throughout, with services to China and South Korea for medical supplies during the initial phase of the pandemic, allowing for frequent profile observations in the Far East. We present an overview of the observations collected so far, and an outlook on the future expansion of the IAGOS-core GHG measurements

How to cite: Gerbig, C., Schultz, U., Seifert, T., Franke, H., Stosius, R., and Nedelec, P.: Update on IAGOS greenhouse gas observations from commercial airliners, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-11067, https://doi.org/10.5194/egusphere-egu22-11067, 2022.

11:02–11:09
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EGU22-5260
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ECS
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On-site presentation
Sieglinde Callewaert, Jérome Brioude, Valentin Duflot, Bavo Langerock, Emmanuel Mahieu, and Martine De Mazière

Réunion is a French island in the Indian Ocean, which holds one of the very few atmospheric observatories in the tropical Southern Hemisphere. Moreover, it hosts experiments providing both ground-based in situ and column Fourier Transform InfraRed spectrometer (FTIR) observations of CO2, CH4 and CO atmospheric concentrations, contributing to the Integrated Carbon Observation System (ICOS), the Network for the Detection of Atmospheric Composition Change (NDACC) and the Total Carbon Column Observing Network (TCCON). This work presents a comprehensive study of these observations made in the capital Saint-Denis and at the high-altitude Maïdo Observatory. We used simulations of the Weather Research and Forecasting model coupled with chemistry (WRF-Chem), in its passive tracer option (WRF-GHG), to gain more insight in the factors that determine these concentrations. Additionally, this study provides an evaluation of the WRF-GHG performance in a region where it has not yet been applied.

This presentation discusses the model set-up and the main findings from the comparisons between the observations and the model simulations, as summarized hereafter.

A comparison of the meteorology near the surface and along atmospheric profiles showed that WRF-GHG has decent skill in reproducing these measurements, especially temperature. Surface CO2 in Saint-Denis follows a distinct diurnal cycle with values up to 450 ppm at night, driven by local anthropogenic emissions, boundary layer dynamics and accumulation due to low wind speeds. Due to an overestimation of local wind speeds, WRF-GHG underestimates this nocturnal buildup. At Maïdo, a similar diurnal cycle is found but with much smaller amplitude. There, surface CO2 is essentially driven by the surrounding vegetation. A high correlation was found between the hourly XCO2 of WRF-GHG and the corresponding TCCON observations. These represent different air masses than those near the surface. They are influenced by processes from distant areas such as Africa and Madagascar. The model shows contributions from fires during the biomass burning (BB) season, but also positive biogenic enhancements associated with the dry season. WRF-GHG fails to reproduce the CH4 observations at Réunion accurately due to a seasonal bias in the background arising from the CAMS reanalysis boundary conditions. Further, local anthropogenic fluxes are the largest source influencing the surface observations at Réunion. However in Saint-Denis, and even more so at Maïdo, the anthropogenic CH4 emissions from EDGAR are likely overestimated. WRF-GHG is able to simulate the CO levels at Réunion with a relative high degree of accuracy. As to the observed XCO, the importance of BB plumes from Africa and elsewhere for explaining the observed variability is confirmed. The surface observations at Maïdo can detect anthropogenic signals from the coastlands during the day and BB enhancements from afar at night, when the Observatory is located in the boundary layer and the free troposphere, respectively.

The high model resolution of 2km is needed to accurately represent the surface observations. Because of the complex topography and local dynamics, an even higher resolution might be needed at Maïdo. To simulate the column observations on the other hand, a model resolution of 50km might already be sufficient.

How to cite: Callewaert, S., Brioude, J., Duflot, V., Langerock, B., Mahieu, E., and De Mazière, M.: Exploitation of greenhouse gas observations at Ile de la Réunion using WRF-Chem simulations, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-5260, https://doi.org/10.5194/egusphere-egu22-5260, 2022.

11:09–11:16
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EGU22-4366
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On-site presentation
Giovanni Bianchini, Marco De Pas, Gianluca Di Natale, Marco Prevedelli, and Luca Palchetti

Since December 2011 the Radiation Explorer in the Far Infrared (REFIR) Fourier trasform spectroradiometer has been operating continuously from the Italian-French station Concordia, in the Dome C region, Antarctica,  providing a decade long dataset of spectrally resolved atmospheric downwelling radiances in the mid/far-infrared range.

In 2016 The Dome C Tropospheric Observatory (DOCTOR) project was established with the aim to recalibrate and reorganize the full time series of REFIR spectra in order to provide a homogeneous dataset, and to make it available to the scientific community.

A further objective of the DOCTOR project has been to integrate the REFIR spectroradiometer with a Lidar sensor to provide coincident, colocated measurements of tropospheric backscatter profiles.

The downwelling radiance spectra are processed with a retrieval code which is capable to provide vertical profiles of tropospheric temperature and water vapor. The availability of coincident backscatter profiles permits to improve the performance of the retrieval in cloudy sky conditions, providing the vertical structure of clouds which is not easily inferred from the spectra alone.

The resulting observation repository will provide a relevant source of information about tropospheric trends in a region, the East Antarctic plateau, which is sparsely covered by ground-based measurements.

How to cite: Bianchini, G., De Pas, M., Di Natale, G., Prevedelli, M., and Palchetti, L.: 10 years of characterization of the troposphere in the East Antarctic plateau region using a ground-based Fourier transform spectroradiometer, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-4366, https://doi.org/10.5194/egusphere-egu22-4366, 2022.

11:16–11:23
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EGU22-5112
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On-site presentation
Xiaoyu Sun, Mathias Palm, and Justus Notholt

The Western Pacific Region has some of the highest sea surface temperatures in the world, described as the Tropical Warm Pool (TWP). It plays a major role in the troposphere-stratosphere exchange and, the chemical composition in the TWP will greatly affect that in the Tropical Tropopause Layer (TTL) and therefore the stratosphere. The FTIR station in Koror, Palau (7.5°N, 134°E) is the only FTIR site in the Warm Pool, which was installed as part of the EU-project StratoClim in 2016. The FTIR station in Paramaribo, Suriname (5.8°N, 55°W) was established as part of the EU-program STAR in 2004. The measurement site in Burgos, Philippines (18.5°N, 120.65°E) (Velazco et al., 2017a) just beside the Warm Pool was installed in 2016. Our analysis of FTIR methane measurements at Palau from 11/2018 – 06/2021 and at Suriname from 01/2017 – 05/2021 with the GEOS-Chem model simulations give some insights into transport processes and the origin of air mass in the TWP. The NDACC retrieved CH4 has good sensitivity to the troposphere and stratosphere. Tropospheric and stratospheric XCH4 are analyzed separately based on the FTIR measurements. Simulations of CH4 from the GEOS-Chem model are used to be compared with the measurements from two tropical sites. The position of the Chemical Equator (Hamilton et al., 2008) calculated from the GEOS-Chem model simulations and FLEXPART are used to investigate the seasonal variations of the CH4 measurements from FTIR.

How to cite: Sun, X., Palm, M., and Notholt, J.: The Origin of Tropospheric Air Masses and related transport processes infer from FTIR measurements and Model Simulations in Western Pacific Region and South America, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-5112, https://doi.org/10.5194/egusphere-egu22-5112, 2022.

11:23–11:30
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EGU22-5736
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ECS
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On-site presentation
Cosimo Fratticioli, Pamela Trisolino, Paolo Cristofanelli, and Francescopiero Calzolari

In order to monitor the contribution of different regions to the atmospheric concentrations of climate-altering gases, the estimate of the atmospheric gas emissions is regularly performed by governmental agencies and is reported into emission inventories. These “bottom-up” emission inventories are generally obtained using country-specific activity data (like population density, land  use, fuel consumptions etc.) and source-specific emission factors. However, these emission estimates can be subjected to large uncertainties, especially for non-CO2 GHGs. This is particularly true for methane (CH4) and some further studies based on the use of atmospheric observations are required in order to provide more precise emissions and/or to validate existing estimations.

Since 2018, hourly mean concentrations of CH4 and CO are produced by using CRDS technique at the Mt. Cimone WMO/GAW global station (CMN, 2165 m a.s.l., Italy) in the framework of ICOS-RI (Integrated Carbon Observation System). Being overlooking the Po basin, atmospheric observations at this measurement site can be used to investigate anthropogenic emissions occurring over this densely inhabited and industrialized region.

In this work, we will present the atmospheric variability of CH4 and CO at CMN during the period May 2018 – December 2020 as obtained from the ICOS dataset 5. Then, we investigate the possibility to use these observations for evaluating the uncertainty related with bottom-up inventories of CH4 emissions over the Po basin. In particular, as based on the approach proposed by Kuwayama et al. 3 , hourly data of CH4 and CO are fitted in order to extract the CH4/CO ratio for each month and each year. Then, the CH4 emissions in the Po basin are estimated by combining the observed CH4/CO ratio with the CO emission extracted by the “state-of art” emission inventories EDGAR (Emissions Database for Global Atmospheric Research) v5.0 and v6.0 1,2 and compared with the national bottom-up inventory 4 produced by ISPRA (Istituto Superiore per la Protezione e la Ricerca Ambientale).

A critical assessment of strengths and caveats of this methodology will be provided and we present the results of sensitivity tests related to the use of different sub-setting of the CMN dataset (in term of observation time and wind direction), to the different methodologies used for CH4/CO calculation, to the ability of the measurement site to be representative for the investigated emission region.

The obtained results show a good agreement with the inventory based emission estimations (both EDGAR and ISPRA)

References

1 European Commission Joint Research Center. Global Air Pollutant Emissions v5.0. https://edgar.jrc.ec.europa.eu/index.php/dataset_ap50, 2019.  

2 European Commission Joint Research Center. Global greenhouse gas emissions v6.0. https://edgar.jrc.ec.europa.eu/index.php/dataset_ghg60, 2020.

3 Kuwayama T. et al. , Source Apportionment of Ambient Methane Enhancements in Los Angeles, California, To Evaluate Emission Inventory Estimates. Environmental Science & Technology, 2019.

4 Istituto Superiore per la Protezione e la Ricerca Ambientale. Disaggregazione dell’inventario nazionale. http://emissioni.sina.isprambiente.it/serie-storiche-emissioni/, 2021.

5 ICOS RI. ICOS Atmosphere Release 2021-1 of Level 2 Greenhouse Gas Mole Fractions of CO2, CH4, N2O, CO, meteorology and 14CO2 (1.0). https://doi.org/10.18160/WJY7-5D06, 2021

How to cite: Fratticioli, C., Trisolino, P., Cristofanelli, P., and Calzolari, F.: Continuous measurements of the CH4/CO ratio at the remote site of Mt.Cimone and their application for the estimate of regional CH4 emissions, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-5736, https://doi.org/10.5194/egusphere-egu22-5736, 2022.

11:30–11:37
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EGU22-10056
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ECS
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On-site presentation
Ceres A. Woolley Maisch, Rebecca E. Fisher, James L. France, David Lowry, Grant Forster, Mathias Lanoisellé, and Euan G. Nisbet

Long term records are vital for understanding the way in which our environment is changing.   

A significant rise in atmospheric methane began in 2007 and has accelerated thereafter, particularly since 2014. This trend was observed globally and was coupled with a sustained isotopic shift to values more depleted in 13C (more negative δ13C-CH4). Currently, there is no consensus as to why these observations have occurred. However, long term methane isotopic measurements can provide information about changes in the source mix of this important greenhouse gas. Here, long term records of both methane mole fraction and  δ13C-CH4 from 5 sites across the UK are presented, showing an increase in CH4 and a decrease in 13C from 2007, similar to those recorded globally, but at the regional-local scale. The approximately weekly in-situ measurements offer an insight into both suburban and background regions of the UK.  

A method for isotopic discrimination from longer term atmospheric measurements of CO2 and  δ13C-CH4 as outlined by Miller and Tans (2003) is utilised in this work. Miller-Tans analysis allows for the explicit specification of background values, vital when dealing with long term records due to both seasonal, local, regional and global background variations in atmospheric CH4 and δ13C-CH4.   

When applying the Miller-Tans method to the long-term data from UK sites, as expected, the heaviest δ13C-CH4 source signatures, which are associated with industrial sources such as gas leaks, are observed for the suburban sites, and biogenic, lighter, sources for the background sites. The methane source distribution is compared to results from mobile measurements carried out at Royal Holloway, University of London and to the UK National Atmospheric Emissions Inventory (NAEI).  

From the initial results, it seems that there is a larger proportion of thermogenic/pyrogenic emissions in this data compared to the NAEI inventory. At all sites, there has been a post 2006 decline in δ13C-CH4. Using the Miller Tans method, it is possible to calculate bulk regional source signatures which highlight a distinction between rural and suburban emissions, in general agreement with the NAEI.

How to cite: Woolley Maisch, C. A., Fisher, R. E., France, J. L., Lowry, D., Forster, G., Lanoisellé, M., and Nisbet, E. G.: Determining UK regional isotopic source signatures of methane using long-term records, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-10056, https://doi.org/10.5194/egusphere-egu22-10056, 2022.

11:37–11:44
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EGU22-3330
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ECS
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Virtual presentation
JeongEun Kim, Jinho Ahn, and Sambit Ghosh

 Quantifying greenhouse gas (GHG) emissions in the megacities is important to mitigating climate change. To characterize the vehicle emissions which is one of the largest contributors to anthropogenic greenhouse gas emissions, we collected air samples from the entry and exit points of the Sang-do Tunnel in Seoul, South Korea in 2021, and measured dry molar mixing ratios of major greenhouse gases spices emitted from vehicles (CO2, CH4, and N2O). The N2O:CO2 emission molar ratio from vehicles is 3.82 ± 0.39 × 10-5, being within a range of 1.8 – 18.7 × 10-5 previously reported in Germany, Switzerland, Sweden, and the USA. The CH4:CO2 emission molar ratio from the vehicles is 33.52 ± 0.43 × 10-5, which is significantly greater than those observed in Switzerland and the USA of 4.6 ± 0.2 × 10–5 and 15 ± 4 ×10–5, respectively. Compared with the calculated Further, we also analyzed δ15N and δ 18O values of N2O from the tunnel air. The δ15N and δ 18O values of N2O emitted from the vehicles are estimated as The newly measured data from Seoul may help us better understand greenhouse gas emissions from vehicles in megacities.

How to cite: Kim, J., Ahn, J., and Ghosh, S.: Greenhouse gas emitted from vehicles in Seoul megacity, South Korea: Molar ratios (N2O:CO2, CH4:CO2) and stable isotopic compositions of N2O, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-3330, https://doi.org/10.5194/egusphere-egu22-3330, 2022.

Lunch break
Chairperson: Euan Nisbet
13:20–13:27
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EGU22-7003
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ECS
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Virtual presentation
Yiyao Wei and Song Gao

As the most effective multinational environmental agreement (MEA), the Montreal Protocol on Substances that Deplete the Ozone Layer has eliminated the production of about 98% of the ozone-depleting substances (ODSs). Moreover, the most recent Kigali Amendment to the Montreal Protocol will phase down the production of hydrofluorocarbons (HFCs) with high global warming potentials. The use of ODSs and HFCs as feedstocks is currently exempted from the control of the Montreal Protocol and its associated amendments because it was falsely assumed that there were no feedstock emissions and that products made from feedstocks were safe in manufacture, use and disposal.

In this paper, we demonstrate a previously missing mechanistic link between ODS and HFC feedstocks and a variety of chemical products that resist environmental degradation, including fluoroplastics and elastomers. We illustrate chemical reaction pathways where specific ODS and HFC gaseous molecules are made into a multitude of macromolecules that pollute the atmospheric, terrestrial and aquatic environments and harm industry workers during the manufacture. For example, the feedstock HCFC-22, itself made from chloroform (an associated feedstock), can be made into polytetrafluoroethylene (PTFE), a fluoroplastic in widespread use. Fluoropolymers’ extreme persistence in the environment and harmful emissions associated with their manufacture and disposal justify curtailing the upstream production of plastics from ODS and HFC feedstocks. We show that a variety of feedstock molecules and their byproducts go into the atmosphere and may alter atmospheric chemical composition.

These reaction mechanisms suggest that ODS and HFC feedstocks be narrowed in their exemptions under the Montreal Protocol, via further amendments and adjustments. Considering also the global warming potential and ozone depletion potential of these feedstocks, this policy response can help mitigate stratospheric ozone depletion, climate change and plastics pollution.

How to cite: Wei, Y. and Gao, S.: Underlying reaction mechanisms support narrowing exemptions of ODS and HFC feedstocks under the Montreal Protocol, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-7003, https://doi.org/10.5194/egusphere-egu22-7003, 2022.

13:27–13:34
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EGU22-5107
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ECS
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On-site presentation
Eric Sauvageat, Eliane Maillard Barras, Klemens Hocke, Alexander Haefele, and Axel Murk

Two decades ago, concentration of ozone-depleting substances in the middle atmosphere started a slow decline as a result of the Montreal Protocol. Since then, stratospheric ozone recovery is expected and has already been observed over some parts of the world, e.g. the Antarctic. Over the mid-latitudes however, the situation is less obvious, and ozone recovery seems to differ depending on the altitude and the geographical area of interest. In view of these uncertainties, there is still a strong need for high-quality and long-term ozone observations and their validation.

Switzerland has a number of stations monitoring ozone using different techniques. In particular, it is the only place in the world with two collocated ground-based ozone microwave radiometers. Located less than 50 km apart, they provide continuous hourly ozone profiles in the middle-atmosphere (~20 to 75 km) since more than 20 years with very few interruptions. Both instrument are part of the Network for the Detection of Atmospheric Composition Change (NDACC) and are regularly used for ozone trend studies or cross validation of satellite observations over Central Europe.

Despite the many studies conducted with these instruments, some anomalous periods and discrepancies in trends were recently identified in their time series. To address these problems, a full harmonization and reprocessing of the data was performed with the aim of obtaining two improved and independent time series. This harmonization affects the calibration of the radiometric measurements, flagging procedures and the retrievals of atmospheric profiles and has now been completed for the last decade.

In this contribution, we present and compare the new harmonized ozone time series for both instruments and highlight the improvements in the ozone retrievals compared to the old data processing. We also perform a comparison of these new data series against measurements from the Microwave Limb Sounder and the Solar Backscatter Ultraviolet Radiometer over Switzerland. As an additional validation, we show some first results of diurnal cycles derived from the new harmonized data series and compare it with model-based diurnal ozone climatology.

How to cite: Sauvageat, E., Maillard Barras, E., Hocke, K., Haefele, A., and Murk, A.: Long-term harmonized ozone profiles in the middle atmosphere over Switzerland , EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-5107, https://doi.org/10.5194/egusphere-egu22-5107, 2022.

13:34–13:41
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EGU22-6083
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ECS
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Virtual presentation
Saswati Das, Scott M Bailey, and Brentha Thurairajah

Sudden stratospheric warmings (SSWs) are dynamic events associated with the rise in stratospheric temperature and the reversal in zonal mean zonal winds. SSWs are driven by large-scale planetary waves that propagate to the stratosphere. These large-scale waves are produced in regions of variable topography such as mountains or due to temperature differences at the warm ocean - cold landmass interfaces. The breaking of the planetary waves propagated to the stratosphere leads to the deceleration and perturbation of the polar vortex circulation, resulting in the sudden increase in polar stratospheric temperature. Due to the highly variable nature of the topography, the northern hemispheric polar vortex is more disturbed by planetary waves than the southern hemisphere. Far more stable winters are seen in the southern hemisphere, with the Antarctic polar vortex in concentric alignment with the south pole terminator.

Despite the usual stability of the southern hemisphere and the infrequency of SSW events, the dynamic event of 2019 was rare and strong, following the likes of the 2002 southern hemispheric SSW. The 2019 SSW event occurred around 29 August and spanned close to three weeks, increasing stratospheric temperature and O3 (ozone) concentration. In this study, we investigate the impacts of the 2019 SSW on the stratosphere using the Solar Occultation for Ice Experiment (SOFIE) instrument onboard the Aeronomy of Ice in the Mesosphere (AIM) spacecraft and other measurements.

SOFIE uses solar occultation to measure solar energy passing through the limb of the earth’s atmosphere at sunrise and sunset. Measurements are typically made at high latitudes (65o-85o N/S) with a vertical field-of-view of ~ 1.6 km covering wavelengths from 0.29 to 5.26 microns. Temperature measurements from SOFIE in 2019 indicate that the average stratospheric temperature during mid-September was higher than in the past years in the 20-30 km altitude range, attributed to the exceptional meteorology during August and September.

In the springtime, stratospheric O3 depletion occurs when polar stratospheric clouds (PSCs) convert halogen reservoir species into O3-destroying reactive forms. The sharp increase in stratospheric temperature during SSWs evaporates PSCs and prevents halogen activation, thus, inhibiting O3 destruction. PSCs are composed of HNO3 (nitric acid) and H2O (water). HNO3 is formed by water reacting with NO2 (nitrogen dioxide), formed by the oxidization of NO (nitric oxide). Thus, using NO and H2O (from SOFIE) as proxies for HNO3, we deduce that both species were higher in 2019 after the SSW than past years’ average during the same period. This indicates a lesser loss of HNO3  to PSCs through denitrification. Consequentially, SOFIE O3 in 2019 (August – mid-October) is significantly higher than the past years’ average, indicating a smaller O3 hole, also reported by NASA O3 watch (for 7 September- 13 October).

This study investigates the 2019 Antarctic O3 enhancement and analyzes the underlying chemistry and mechanism using SOFIE and other measurements.  

How to cite: Das, S., Bailey, S. M., and Thurairajah, B.: Investigation of the Ozone Enhancement during the 2019 Sudden Stratospheric Warming in the Southern Hemisphere, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-6083, https://doi.org/10.5194/egusphere-egu22-6083, 2022.

13:41–13:48
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EGU22-9242
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ECS
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Presentation form not yet defined
Ozone simulations with ICON for the improvement of UV predictions
(withdrawn)
Simon Weber, Roland Ruhnke, Christian Scharun, Axel Seifert, and Peter Braesicke
13:48–13:55
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EGU22-10907
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Presentation form not yet defined
Sean Davis, Karen Rosenlof, and Yue Jia

In this presentation, we summarize recent improvements to the Stratospheric Water and Ozone Satellite Homogenized (SWOOSH) database. SWOOSH is primarily a monthly mean zonal mean merged data set of vertically resolved ozone and water vapor data from a subset of limb profiling instruments operating since the 1980s. This presentation details recent updates and improvements made to SWOOSH to include additional sources of data and improve uncertainty estimates. The improvements to SWOOSH include new efforts to better account for uncertainties related to sparse sampling and inconsistent error estimates among different satellite sensors. We also assess the impact on variability and trends of incorporating three new satellite sensors to SWOOSH (ACE-FTS, SAGE III/ISS, and OMPS-Limb Profiler), as well as from including the new Aura MLS version 5 data. With the expected loss of the Aura MLS instrument sometime in the mid 2020’s, the addition of these new instruments will help continue the SWOOSH record into the future.

How to cite: Davis, S., Rosenlof, K., and Jia, Y.: Improvements to the Stratospheric Water and OzOne Satellite Homogenized (SWOOSH) data set and implications for ozone and water vapor variability and trends, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-10907, https://doi.org/10.5194/egusphere-egu22-10907, 2022.