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. Both approaches contribute to improved understanding of the mechanisms that control the variability of atmospheric chemical composition (including multiple gaseous species). Presentations related to the projections of the atmospheric composition are welcome in this session as well.
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.
vPICO presentations: Tue, 27 Apr
Recent years have brought a significant increase in public awareness of the issue of poor air quality in Poland. It is understandable that this problem has a direct impact on the quality of life of citizens of this country. Over the last few decades a concern over the health effects associated with air pollution was growing, mainly due to their carcinogenic and mutagenic properties. Various actions initiated by non-governmental organizations forced the authorities to undertake certain measures aimed at improving the quality of air in Poland, which, in the reports of the European Environment Agency is listed as one of the most polluted countries in the entire European Union. A model example here is the Krakow agglomeration. The city, located in a basin extending in the Vistula valley, surrounded on three sides by hills, in the cold period of the year struggles with the problem of poor air quality (very high concentrations of particulate matter and benzo(a)pyrene).
The objective of this research was better characterization of two major elements responsible for poor air quality in Krakow agglomeration: existing sources of pollution and local meteorology during heating season (HS) and non-heating season (NHS). Samples were collected with 24h resolution using Low-Vol samplers in Krakow (50°00'38.1"N 19°56'57.1"E, Kurdwanow, Malopolska, South Poland) from February 2014 to January 2015. Based on the results of polycyclic aromatic hydrocarbons, cations, anions, mercury, organic and elemental carbon analyzes of samples of particulate matter collected in the city’s atmosphere, sources have been identified and classified them from the most to the least significant ones. The modeling tool Hybrid Single-Particle Lagrangian Integrated Trajectory model (HYSPLIT), developed by NOAA’s Air Resources Laboratory, was used to investigate the possible trajectories of air pollutants.
This research was partially financed by the AGH UST grant 126.96.36.1996 subsidy of the Ministry of Science and Higher Education. PF and AS have been partly supported by the EU Project POWR.03.02.00-00-I004/16. The infrastructure of the AGH Center of Energy in Kraków was applied in order to determine the concentration of ions.
How to cite: Furman, P., Skiba, A., Samek, L., Zimnoch, M., Kistler, M., Kasper-Giebl, A., Gilardoni, S., and Styszko, K.: Chemical characteristics of particulate matter - problem of Polish cities with air pollution, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-10687, https://doi.org/10.5194/egusphere-egu21-10687, 2021.
Two fractions of suspended particulate matter (PM1 and PM10) were collected on daily basis in the urban atmosphere of Krakow, southern Poland, during one-year period (April 2018 - April 2019). The following compounds were examined: elemental carbon (EC), organic carbon (OC), carbohydrates (among them levoglucosan – a recognized biomass tracer), as well as ions (Li+, Na+, NH4+, K+, Mg2+, Ca2+, F-, Cl-, NO2-, Br-. NO32-, PO43-, SO42-). Thermal-optical analysis with a Sunset carbon analyzer, (Sunset Lab. Inc.) was used to obtain information about organic and elemental carbon concentration, while HPAE-PAD Dionex ICS 3000 system was employed to determine the concentration of 14 carbohydrates. Concentration of ions was analysed using isocratic ion chromatography on an ICS-1100 instrument (Thermo Scientific).
Distinct seasonality of chemical composition of PM1 and PM10 fraction was observed. Levoglucosan concentration ranged from 0.01 ug/m3 to 0.90 ug/m3 (PM1 fraction) and from 0.01 to ug/m3 to 1.95 ug/m3 (PM10 fraction) during the analysed period. Arabitol and Mannitol were detected only in PM10 fraction and ranged from 0.01 ug/m3 and 0.02 ug/m3, during winter season and to 0.15 ug/m3 and 0.10 ug/m3, respectively, during summer season. Significant seasonal differences were also found for ion concentrations: from 0.49 μg/m3 (SO42-), 0.15 μg/m3 (NO3-) and 0.05 μg/m3 (NH4+) during summer season, to be compared with 11.16 μg/m3 (SO42-), 9.30 μg/m3 (NO3-), 9.25 μg/m3 (NH4+) for winter season. The concentration of organic and elemental carbon in PM10 fraction ranged from 2.0 μg/m3 to 48.9 μg/m3 (OC) and from 0.3 μg/m3 to 10.0 μg/m3 (EC), to be compared with 1.4 μg/m3 to 18.1 μg/m3 (OC) and 0.2 μg/m3 to 4.4 μg/m3 (EC) for PM1 fraction.
The presented work was funded by Polish National Science Centre (project No. 2019/33/N/ST10/02925) as well as COST Action COLOSSAL (CA16109) of EU. Work of AS and PF have been partly supported by the EU Project POWR.03.02.00-00-I004/16. Analytical infrastructure of AGH Center of Energy in Krakow was employed in analyses of selected ions.
How to cite: Skiba, A., Furman, P., Styszko, K., Kasper-Giebl, A., Tobler, A., Casotto, R., Prevot, A., and Różański, K.: Chemical composition of PM1 and PM10 fraction collected in urban atmosphere of Krakow, southern Poland during 2018-2019 period, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-11013, https://doi.org/10.5194/egusphere-egu21-11013, 2021.
The study investigates the chemical composition and source of aerosol origin at a semi-urban (Kharagpur–Kgp) and urban (Kolkata–Kol) region during the period February 2015 to January 2016 and September 2010 to August 2011 respectively. Major water-soluble inorganic aerosols (WSII) were determined using Ion chromatography and carbonaceous aerosols (CA) using OC–EC analyser. A multivariate factor analysis Positive Matrix Factorization (PMF) was used in resolving source of aerosols at the study locations. Seasonal analysis of WSII at Kgp and Kol indicated relative dominance of calcium at both the places followed by sodium, chloride, and magnesium ions. Non-sea salt potassium (nss–K+), a biomass burning tracer was found higher at Kol than at Kgp. Sum of secondary aerosols sulphate (SO42-), nitrate (NO3-) and ammonium (NH4+) was higher at Kol than Kgp with relative concentration of SO42- being higher than NO3- at Kgp which was vice-versa at Kol. Examination of carbonaceous aerosols showed three times higher concentration of organic carbon (OC) than elemental carbon (EC) with monthly mean of OC/EC ratio > 2, indicating likely formation of secondary organic carbon formation. Seasonal influence of biomass burning inferred from nss–K+ (OC/EC) ratio relationship indicated dissimilarity in seasonality of biomass burning at Kgp (Kol). PMF resolved sources for Kgp constituted of secondary aerosol emissions, biomass burning, fugitive dust, marine aerosols, crustal dust and emissions from brick kilns while for Kol factors constituted of burning of waste, resuspended paved road dust, coal combustion, sea spray aerosols, vehicular emissions and biomass burning.
How to cite: Dubey, K. and Verma, S.: Investigation of atmospheric aerosols over semi-urban and urban areas in Eastern Indo-Gangetic Plain: seasonal variability and source apportionment using PMF, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-14205, https://doi.org/10.5194/egusphere-egu21-14205, 2021.
Mountain and high-altitude sites provide representative data for the lower free troposphere and various pathways for aerosol interactions, changing boundary layer heights useful in understanding atmospheric composition. However, few studies exist in African regions despite its diversity in both natural and anthropogenic emissions. For this reason, the ATLAS Mohamed V (AM5) observatory in the Middle Atlas region was established to provide the necessary infrastructure for detailed atmospheric studies in the North African high-altitude region. Here, results of a field study conducted to determine the aerosol chemical composition in this region, understand its variations, and importance in assessing global and regional changes in the atmospheric composition is reported. Particulate matter (PM10) filter samples (200) were collected using a high-volume (500l/min) collector in a 12h sampling interval from August to December 2017. The chemical composition of the samples was analyzed for trace metals, ions, elemental carbon, organic carbon, aliphatic hydrocarbons, and polycyclic aromatic hydrocarbon (PAHs) content. The results show that the high-altitude aerosol composition is influenced by regional and transregional transport of different pollutants. Local sources play an important role during periods when the wind speed is low, especially during autumn. Despite the proximity of the site to the Saharan Desert, its influence on the atmospheric composition was mainly seasonal and accounted for only 14% of the sampling duration. The chemical composition was dominated by inorganic elements, mainly suspended dust (47%) and ionic species (16%), and followed by organic matter (15%), water content (12%), and indeterminate mass (9%). Biogenic organics contributed up to 7% of the organic matter with high contributions from compounds such as Nonacosane, Heptacosane, and 2-Pentadecanone. Four main air masses characterized the inflow to the site, which often leads to different aerosol chemical compositions. Mineral dust influenced was seasonal and ranged between 20 and 70% of the PM mass with peaks observed during the summer and was accompanied by high concentrations of SO42- of up to 1.3 µg/m³. PM10 concentrations during winter were low (< 30 µg/m³), with a dominance of marine air masses (53%) carrying aerosols rich in sea salt and polluted anthropogenic aerosols from the coastal regions (Rabat and Casablanca). During the day-time, mineral dust contribution to PM increased by about 42% due to road dust resuspension. In contrast, during night-time, an increase in the concentrations of PAHs, ketones, and anthropogenic metals such as Pb, Ni, and Cu was found due to variations in the boundary layer height. The results provide first insights into typical North African high-altitude background aerosol chemical composition useful for long-term assessment of climate and regional influence of air pollution in North Africa.
How to cite: Deabji, N., Fomba, K. W., El Hajjaji, S., Mellouki, A., and Herrmann, H.: Aerosol chemical composition of the middle Atlas region of North Africa, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-14700, https://doi.org/10.5194/egusphere-egu21-14700, 2021.
The Indo-Gangetic Plain (IGP) is one of the world’s most populated river basins housing more than 700 million people. Apart from being a major source region of aerosols, the IGP is affected by transported aerosols from the Thar Desert, forest-fires and open burning of crop waste from central India. Studies have been carried out to understand the aerosol chemical composition and optical properties in source regions of IGP but knowledge is severely lacking for receptor locations viz. eastern IGP (eIGP). To address this, the present study reports the seasonal variability of carbonaceous and ionic species in ambient PM2.5 from a rural receptor location (Mohanpur, West Bengal) along with insights on aerosol acidity, its neutralization and potential source regimes. A total of 88 PM2.5 samples collected during the summer, post-monsoon and winter seasons of 2018 were analyzed for SO42-, NO3-, Cl-, Na+, NH4+, K+, Ca2+, Mg2+, F-,PO43-, water-soluble organic carbon (WSOC), organic carbon (OC) and elemental carbon (EC) fractions. Sulfate, nitrate and ammonium (SNA) were the dominating ionic species throughout the seasons (67-86% out of the total ionic species measured). Significant positive Cl- depletion in summer (49±20%) pointed towards influx of marine air while negative depletion in post-monsoon and winter suggested a biomass burning (BB) source, which was further supported by concentration-weighted trajectory analysis. Strong acidity was found to be highest during post-monsoon (141±76 nmol m-3), followed by winter (117±36 nmol m-3) and summer (40±14 nmol m-3) with significant differences between summer and the other seasons. Neutralization factor (Nf) and equivalent charge ratio of cation to anion (RC/A) revealed that summertime aerosols were neutral in nature while those of post-monsoon and winter were comparatively acidic with NH4+ being the major neutralizing agent throughout the seasons. Correlations between WSOC and OC fractions (OC1, OC2, OC3 and OC4) suggested secondary formation of summertime WSOC (WSOC vs OC3: r=0.48, p<0.05) via photochemical oxidation of volatile organic carbons (VOCs) while that of post-monsoon (WSOC vs OC1, OC2, OC3: r=0.45-0.62, p<0.05) and winter (WSOC vs OC1, OC2, OC3: r=0.58-0.68, p<0.05), both primary and secondary pathways seem important. To elucidate the role of BB, we looked into the two components of EC i.e., char-EC (EC1-PC) and soot-EC (EC2+EC3). The percent contribution of char-EC to EC was 65±17%, 90±10% and 98±1% during summer, post-monsoon and winter, respectively. Along with this, char-EC/soot-EC ratios of 2.3±1.8, 17.6±16.4 and 50.3±18.6 during summer, post-monsoon and winter, respectively, and significant correlations of the same with the BB-tracer K+ (post-monsoon: r=0.78, p<0.001; winter: r=0.64, p<0.01) indicated the importance of BB emissions in constraining carbonaceous aerosol profiles during post-monsoon and winter.
How to cite: Sharma, B., J. Polana, A., Mao, J., Jia, S., and Sarkar, S.: Variation in carbonaceous and ionic species at a rural receptor location in the eastern Indo-Gangetic Plain, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-7205, https://doi.org/10.5194/egusphere-egu21-7205, 2021.
Atmospheric aerosols are an essential climate forcing agent and play a critical role in global climate change. Its effect on Earth’s radiative budget is determined by their optical properties, it is, the scattering and absorption coefficients. The ability of the aerosol to interact with solar radiation is dependent upon particle size and composition, both related to variation in sources. By scattering the solar radiation, the aerosols contribute to the cooling of the underlying atmosphere and the surface; by absorbing the solar radiation, they contribute to the heating of the atmosphere. Different techniques have been developed to measure and characterize different properties of the aerosols in the column and at surface level. At surface level, nephelometers have predominantly been used to measure light scattering properties.
In 2017, two nephelometers Aurora 3000, manufactured by Ecotech Company, where deployed at the Burjassot campus from the University of Valencia, for the determination of the total scattering coefficients in wet and dry conditions. In 2019, an Ecotech Aurora 4000 polar nephelometer was added in the Burjassot site for the determination of the scattering coefficients at different angle intervals. The Aurora 4000 model has been specifically designed with a backscatter shutter that can be set any angle between 10º and 90º at up to 17 different positions. It then has the ability to improve the determination of the aerosol asymmetry parameter. Measurements of the total scattering coefficient at ambient conditions, performed with a TSI 3563 nephelometer without sample conditioning, are also available since 2006.
The Burjassot measurement site is located in the suburbs of Valencia city, with a total population of about 1 million inhabitants in its metropolitan area, and it is representative of urban conditions. It is mainly affected by anthropogenic aerosols originated by traffic, and sporadically regional agricultural or forest fires, but also by natural aerosols of marine (Mediterranean Sea) and desert (Saharan) origin.
In this work, we analyze the total and angular measurements of the scattering coefficient obtained with the total and polar Aurora nephelometers at Burjassot site, including its temporal variability and trends. Specific scenarios characterized by different atmospheric conditions are also studied in order to relate in situ measurements with the composition of atmospheric aerosols from different sources (Saharan dust, forest fires, traffic, etc).
This work is supported jointly by the Spanish Ministry of Economy and Competitiveness (MINECO) and the European Regional Development Fund (FEDER) under Projects CGL2017-86966-R, RTI2018-096548-B-I00 and PRE2018-084799.
How to cite: Matos Tejera, V., Camarasa Fayos, J., Esteve Martínez, A. R., Estellés Leal, V., Utrillas Esteban, M. P., and Martínez-Lozano, J. A.: Analysis of the integrated and angular aerosol scattering coefficients at Valencia (Spain), EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-10925, https://doi.org/10.5194/egusphere-egu21-10925, 2021.
The atmospheric aerosols have an important role in the radiative forcing in the atmosphere. The solar radiation interacts with the aerosols, being absorbed or scattered in different directions, depending on the absorption and scattering coefficients. The scattering coefficient is highly dependent on the aerosol size, this being dependent on the relative humidity of air, if the aerosols are hygroscopic. The aerosol hygroscopic factor, f(RH), is the factor describing how the scattering coefficient depends on the relative humidity.
To understand the relation between scattering coefficients of aerosols and the relative humidity of air, and thus improving our estimations of the radiative effect of urban aerosols, we recently started to measure the aerosol hygroscopic factor, extending previous data series of scattering and absorption properties obtained at our Burjassot site, in Valencia (Spain). Preliminary results already showed values of fRH (75%) between 1.13-1.31.
In this study we are interested on analysing the effect of the air mass type on the aerosol properties at our site, mainly on the total scattering coefficients and the hygroscopic factor, so we can understand if the trajectory of the air masses carrying the aerosols influences their hygroscopic properties at our region.
The area represented by our station is mainly of urban coastal character. The Burjassot site is located in the suburbs of Valencia city in Spain. The population of the metropolitan area of Valencia is about 1 million. The distance to the Valencia city centre is about 5 km southeast, and the distance to the seacoast is about 10 km east. The site is locally affected by the traffic pollution, but also affected by light industry and occasional agricultural or forest fires.
The scattering coefficient measurements at ambient conditions were started at Burjassot site on the late 06’s, by means of a three channel TSI 3563 nephelometer. In 2017, an ACS 1000 (Aerosol Conditioning System, manufactured by Eco Tech Company) with a tandem of Aurora 3000 nephelometers for dry and wet channels were added, although technical problems with the wet channel prevented us to obtain useful results before 2019. Additionally, angular scattering coefficients are simultaneously measured at ambient conditions only, with an Aurora 4000 polar nephelometer, available since 2019.
In the current analysis, we use a well-known trajectory computing model like HYSPLIT to determine the path of the air masses during the last 5 days before its arrival at our station. Then, the numerical backtrajectories are automatically analysed by the application of previously developed algorithms to derive the type of dominant air mass, and its origin. Finally, the scattering coefficients and hygroscopic factors are classified in relation to the air mass type, to understand how these aerosol properties are linked to the main air mass types that influence our region.
This work is supported jointly by the Spanish Ministry of Economy and Competitiveness (MINECO) and the European Regional Development Fund (FEDER) under Projects CGL2017-86966-R and RTI2018-096548-B-I00.
How to cite: Camarasa, J., Matos, V., Estellés, V., Utrillas, M. P., and Martínez-Lozano, J. A.: Analysis of the air mass dependency of the aerosol hygroscopic factor at Burjassot, Spain, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-10929, https://doi.org/10.5194/egusphere-egu21-10929, 2021.
The Arctic region is particularly sensitive to global climate change, experiencing warming at twice the rate of the global average. Anthropogenic pollution (e.g. aerosols, black carbon, ozone, and greenhouse gases), which to a large extent originates from the mid-latitudes, is suspected to be partly responsible for this warming. Atmospheric aerosols can alter the planetary radiation balance directly through scattering and absorption and indirectly through modification of cloud properties. These interactions depend on aerosol physicochemical properties. The Arctic cryosphere and atmosphere has undergone significant changes in recent decades, accompanied by reductions in anthropogenic emissions, especially in Europe and North America. These changes have important ramifications for the ambient Arctic aerosol. 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 recent trends for aerosol particle physical properties, which will aid in this understanding of the changing Arctic.
Measurement Site & Methods
All measurements were obtained at Villum Research Station (Villum, N 81o36’ W 16o39’ 24 m a.s.l) in northeastern Greenland. Particle number size distributions (PNSD) were measured using a Scanning Mobility Particle Sizer (SMPS) from 2010–2018.
We have utilized mode fitting on daily averaged PNSDs to characterize three distinct modes (Nucleation, Aitken, and Accumulation) along with geometric mean diameters (GMD) and number concentrations (PN) for each mode.
The trends in these parameters were identified and quantified using the Mann-Kendal test and Theil Sen slope on the 90th % confidence interval. Trends in different months were analyzed using daily modal parameters.
Statistically significant (s.s.) decreasing trends were detected for the Nucleation and Aitken modes GMDs in the winter, spring, and summer, with the only s.s. increasing trends occurring in the autumn. The Accumulation mode GMD showed a s.s. decrease in the spring and s.s. increase in the summer. For the PN of each mode, large s.s. increasing trends were detected for Nucleation and Aitken mode PN in the spring and summer. The Accumulation mode PN showed a small s.s. increase in the summer and a large s.s. decrease in the autumn.
These results show that ultrafine modes (Nucleation and Aitken) are decreasing in diameter while simultaneously increasing in number concentration. These trends are most likely related to changes in sea ice extent, as previous research has indicated a negative correlation between new particle formation and sea ice extent. The decrease in Accumulation mode GMD in spring (during the peak of the Arctic Haze) is possibly related to decreases in anthropogenic emissions, while the increase PN during summer could signal an increase in primary biogenic aerosol emissions from the ocean surface. The large decrease in Accumulation mode PN during autumn requires further investigation.
This work will help confirm trends of other aerosol components observed at other High Arctic sites and can offer insight into the climatic implications (i.e., radiative balance and cloud properties) for a future Arctic climate.
How to cite: Pernov, J., Skov, H., Thomas, D., and Massling, A.: Trend analysis of aerosol particle physical properties at Villum Research Station, Northern Greenland, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-12767, https://doi.org/10.5194/egusphere-egu21-12767, 2021.
Dust Aerosol Optical Depth (DAOD) is considered as one of the main sources of uncertainty in the assessment of climate change. In this talk, we present results of DAOD trend over the Eastern Mediterranean (EM) region in the dusty season (April- May- June- and July: AMJJ) during the years 2003-2019 using long-term DAOD from the Modern-Era Retrospective analysis for Research and Applications, Version 2 (MERRA-2) and the Copernicus Atmosphere Monitoring Service Reanalysis (CAMSRA). MERRA-2 and CAMSRA DAOD displayed significant positive trends during the years 2003-2010 over the region at the rates of 0.007 year−1 and 0.005 year−1, respectively. In contrast, significant negative MERRA-2 and CAMSRA DAOD trends occurred during the years 2010 -2017 with the rates of -0.009 year−1 and -0.004 year−1, respectively. Moreover, trend analysis was also attempted for the Angstrom Exponent (AE440-870) and Fine Mode Fraction (FMF500) from 3 AERONET sits in the region. AERONET data are compatible with the trend of MERRA-2 and CAMSRA DAOD. This suggests that the aerosols trend on the EM region is influenced by aeolian dust level.
How to cite: Shaheen, A., Wu, R., and Yousefi, R.: Dust Aerosol trends over the Eastern Mediterranean region during 2003-2019, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-582, https://doi.org/10.5194/egusphere-egu21-582, 2021.
With rapid economic growth and urbanization, air pollution episodes with high levels of particulate matter (PM2.5) have become common in China. While emissions of pollutant precursors are important, meteorology also plays a major role in pollution episodes, especially in winter. We examine the influence of the dominant large-scale circulation and the key regional meteorological features on PM2.5 over three major regions of China: Beijing–Tianjin–Hebei (BTH), the Yangtze River Delta (YRD), and the Pearl River Delta (PRD). The East Asian winter monsoon (EAWM) is primarily studied, including some of its main large-scale components such as the East Asian trough and the Siberian high, as it influences PM2.5 differently in different parts of China. In the BTH region, the shallow East Asian trough curbs the invasion of northerly cold and dry air from the Siberian high which induces high relative humidity and heavy pollution, possibly via relative humidity-promoted aerosol formation and growth. A weak southerly wind in Eastern and Southern China associated with a weakened Siberian high suppresses horizontal dispersion, contributing to pollution accumulation over YRD. In addition, the El Niño-Southern Oscillation (ENSO) as the dominant mode of global ocean-atmosphere interaction has a substantial modulation on precipitation over southern China. In the PRD, weak southerly winds and precipitation deficits over southern China are conducive to atmospheric pollution possibly via reduced wet deposition. Furthermore, we construct new circulation-based indices based on the dominant large-scale circulation: a 500 hPa geopotential height-based index for BTH, a sea level pressure-based index for YRD and an 850 hPa meridional wind-based index for PRD. These three indices can effectively distinguish different levels of pollution over BTH, YRD and PRD, respectively. We also show how additional regional meteorological variables can improve the prediction of regional PM2.5 concentrations for these three regions. These results are beneficial to understanding and forecasting the occurrence of severely polluted days for BTH, YRD and PRD from a large-scale perspective.
How to cite: Jia, Z., Doherty, R., Ordóñez, C., Li, C., and Wild, O.: The impact of large-scale circulation on daily fine particulate matter (PM2.5) in major populated regions of China during winter , EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-13663, https://doi.org/10.5194/egusphere-egu21-13663, 2021.
The serene environment of the Himalayas is experiencing adverse impact of air pollution, rising critically with the advent of rapid industrialization and urbanization. However, systematic long-term ground-based measurements are almost nonexistent in this region due to the prevailing extreme conditions and complex terrain.
In this context, we present insights from the long term ground based measurements of aerosols and trace gases carried at ARIES, (29.4oN, 79.5oE, 1958 m a.m.s.l) a high altitude site in the Central Himalayas. We also used satellite observations, back-air trajectories and radiative forcing estimations with these extensive observations to understand the variabilities, sources and radiative impact over this region. The higher temporal resolution online measurements during 2014-2020 revealed that daytime concentrations of OC, EC, CH4 and CO were twice that of the night-time. It is shown that swiftly varying meteorological parameters along with boundary layer height during daytime are responsible for these changes at diurnal scales. Diurnal observations of EC are used to estimate radiative forcing (RF) and it is shown that atmospheric RF during afternoon is about 70% higher than the forenoon RF.
Residence time and concentration weighted trajectory analysis along with OC/EC ratio and fire estimates from MODIS show the influence of biomass burning in spring (MAM). Seasonal minimum for all the species occurs in the monsoon (JJA) due to extensive wet scavenging at the site. During winter (DJF), influence of local burning activities for heating and cooking, to aide in lower temperatures is shown.
Source apportionment estimate is used in BC and multiple regression approach is used in CO to segregate their biomass (BCbb/ CObb), fossil fuel (BCff/ COff) and background components (CObgd) components. The results reveal the dominance of fossil fuel emissions in BC (BCff ~76% BCbb ~24%) and background component in CO followed by fossil fuel emissions (CObgd ~59%, COff ~26%, CObb ~14%). Principal component analysis (PCA) applied to 23 chemical constituents of PM10 samples collected during October 2018−February 2019 identified the contribution of crustal/soil dust, biomass burning and industrial emissions at the site. Further, long term (2006-2020) aerosol properties acquired from the CALIPSO is used to study the vertical structure of aerosols and their subtypes and it is shown that the fine mode aerosols with particle depolarization ratio < 0.2 dominate the site.
The study thus utilizes the long term dataset to precisely segregate the role of local meteorological conditions, transport, fossil fuel, biomass burning and local emissions impacting the site in different seasons and shows its particular importance in terms of radiation budget and constraining emission sources.
How to cite: Srivastava, P., Naja, M., Joshi, H., Gogoi, M. M., and Babu, S. S.: Characterization of aerosols and trace gases at the Central Himalayas using long-term ground and satellite observations , EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-7912, https://doi.org/10.5194/egusphere-egu21-7912, 2021.
Launched among growing concerns about air pollution in India, the National Clean Air Program (NCAP) 2019 aims to reduce PM2.5 concentrations by 20-30% by 2024, relative to 2017. This analysis is an overview of air pollution levels in India in the five years prior to implementation of the NCAP program and provides a baseline to evaluate its future success. We analyze ground observations from 2015 – 2019, of five criteria pollutants – PM10, PM2.5, SO2, NO2 and O3. We use data retrieved from the continuous and manual monitors across India to calculate annual average concentrations, seasonal cycles and monthly variability of these five pollutants in northern and southern India (divided at 23.5 oN). We find that northern India has (7%-129%) higher average concentrations of all pollutants compared with southern India, except for SO2 where the concentrations are similar. Particulate pollution dominates the pollution mix with virtually all sites in the northern region failing to meet the annual average PM10 and PM2.5 national ambient air quality standards (NAAQS) (of 60 g/m3 and 40 g/m3, respectively) while some sites in southern India meet the standard. Although inter-annual variability exists, no significant trend of these pollutant concentrations was observed over the five-year period. We also conduct case studies in five cities included in the US State Department Air-Now PM2.5 network - Delhi, Kolkata, Mumbai, Hyderabad and Chennai and include continuous monitoring data. We find the annual average PM10 and PM2.5 NAAQS concentrations to be frequently exceeded in these cities with highest concentrations found in Delhi, followed by Kolkata. SO2 concentrations, however, generally meet the NAAQS standard in all the five cities. NO2 NAAQS are exceeded in Delhi, Kolkata and Hyderabad in winter whereas O3 only occasionally exceeds NAAQS in Delhi. Our work creates a framework that can be used in future research to evaluate the success of the NCAP air pollution mitigation program.
How to cite: Sharma, D. and Mauzerall, D.: Analysis of Surface Air Pollutant Measurements from 2015-2019 in India, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-8938, https://doi.org/10.5194/egusphere-egu21-8938, 2021.
European cities have made significant progress over the last decades towards a clean air. Despite all this progress, several urban areas are frequently exceeding air quality levels allowed by the European legal standards. The ClairCity project funded by the H2020 program addressed air pollution bringing a key missing factor in the way cities and societies organized themselves and work: citizens at the heart not only of the air pollution issues, but also of the solution, focusing on their behaviour, activities and practices. In this work, the ClairCity European pilot cities and regions (Bristol in the UK, Amsterdam in the Netherlands, Ljubljana in Slovenia, Sosnowiec in Poland, the Aveiro region in Portugal and the Liguria region around Genoa in Italy) are studied in terms of air quality for a 10 year period regarding the main atmospheric pollutants over urban areas, namely particulate matter, nitrogen dioxide and ozone.
Therefore, the main objective of this work is to present a comprehensive diagnosis of the air quality and its main emission sources for each case study. The concentrations trends in the different typology of monitoring stations (background, traffic and industrial) were addressed, together with the knowledge of daily, weekly and seasonal pollution patterns to better understand the city specific profiles and to characterise pollutant dynamics and variations in multiple locations.
Each city/ region faces different issues and causes of air pollution, but all of these case studies have been working on to improve their air quality. In Bristol there have been strong downward trends in many air pollutants, but the levels of NO2 remain persistently high and of concern, with transport the key contributor. PM on the other hand is not widely monitored in Bristol, but background levels at least are under limit values. Similarly, the main sources of air pollution in Amsterdam are traffic, in particular for NO2, and international shipping. Decreasing emissions and concentration levels point to some success of Amsterdam air quality policies in recent years. PM10 exceedances are a seasonal pollution problem in Ljubljana, with the main particulate matter sources attributed to residential heating, which is still significantly outdated in some parts of the city, where households still heat with burning wood and biomass during winter. The most pressing issue for air quality within Sosnowiec is emissions from residential heating. Particulate matter are the main critical pollutants, linked with the use of inefficient heating systems, together with poor quality fuels, in winter. On the other hand, NO2 limit values are also exceeded in Sosnowiec, but in comparison to the low-stack emissions, the problem is far smaller. On contrary, air quality in the Aveiro region is relatively good, due to an overall relatively low population density in the region, and an open landscape in a maritime climate. PM10 and O3 exceedances do occur occasionally. While, exceedances of NO2 and O3 concentrations are still problematic in Liguria region, with road transport, industrial plants and port activities being the main contributors to these problems.
How to cite: Rodrigues, V., Gama, C., Ascenso, A., Oliveira, K., Coelho, S., Monteiro, A., Hayes, E., and Lopes, M.: Temporal patterns and trends of air pollution over distinct European urban areas, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-9303, https://doi.org/10.5194/egusphere-egu21-9303, 2021.
One way to form aerosol particles is the condensation of oxidized atmospheric trace gases, such as sulfuric acid (SA) into small molecular clusters. After growing to larger particles by condensation of low volatile gases, they can affect the planets climate directly by scattering light and indirectly by acting as cloud condensation nuclei. Observations of low-volatility aerosol precursor gases have been reported around the world but long-term measurement series and Arctic data sets showing seasonal variation are close to non-existent. In here, we present ~7 months of aerosol precursor gas measurements performed with the nitrate based chemical ionization mass spectrometer (CI-APi-TOF). We deployed our measurements ~250 km above the Arctic Circle at the Finnish sub-Arctic field station, SMEAR I in Värriö. We report concentration measurements of the most common new particle formation related compounds; sulfuric acid, methanesulfonic acid (MSA), iodic acid (IA) and highly oxygenated organic compounds, HOMs. At this remote measurement site, surrounded by a strict nature preserve, that gets occasional pollution from a Russian city of Murmansk, SA is originated both from anthropogenic and biological sources and has a clear diurnal cycle but no significant seasonal variation, while MSA as an oxidation product of purely biogenic sources is showing a more distinct seasonal cycle. Iodic acid concentrations are the most stable throughout the measurement period, showing almost identical peak concentrations for spring, summer and autumn. HOMs are abundant during the summer months and due to their high correlation with ambient air temperature, we suggest that most of HOMs are products of monoterpene oxidation. New particle formation events at SMEAR I happen under relatively low temperatures, low relative humidity, high ozone concentration, high SA concentration in the morning and high MSA concentrations in the afternoon. The role of HOMs in aerosol formation will be discussed. All together, these are the first long term measurements of aerosol forming precursor from the sub-arctic region helping us to understand atmospheric chemical processes and aerosol formation in the rapidly changing Arctic.
How to cite: Jokinen, T., Lehtipalo, K., Neitola, K., Sarnela, N., Laitinen, T., Kulmala, M., Petäjä, T., and Sipilä, M.: Composition and concentrations of aerosol precursor gases in the sub-Arctic boreal forest, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-12140, https://doi.org/10.5194/egusphere-egu21-12140, 2021.
Open biomass burning (BB) is a globally widespread phenomenon. The fires release pollutants, which are harmful for human and ecosystem health and alter the Earth's radiative balance. Yet, the impact of various types of BB on the global radiative forcing remains poorly constrained concerning greenhouse gas emissions, BB organic aerosol (OA) chemical composition and related light absorbing properties. Fire emissions composition is influenced by multiple factors (e.g., fuel and thereby vegetation-type, fuel moisture, fire temperature, available oxygen). Due to regional variations in these parameters, studies in different world regions are needed. Here we investigate the influence of seasonally recurring BB on trace gas concentration and air quality 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.) and is well suited to study the large-scale fires on the Indochinese Peninsula, whose pollution plumes are frequently transported towards the site . We present continuous trace gas observations of CO2, CH4, CO, and O3 conducted at PDI since 2014 and interpret the data with atmospheric transport simulations. Annually recurrent large scale BB leads to hourly time-scale peaks CO mixing ratios at PDI of 1000 to 1500 ppb around every April since the start of data collection in 2014. We complement this analysis with carbonaceous PM2.5 chemical composition analyzed during an intensive campaign in March-April 2015. This includes measurements of elemental and organic carbon (EC/OC) and more than 50 organic markers, such as sugars, PAHs, fatty acids and nitro-aromatics . For the intensive campaign, we linked CO, CO2, CH4 and O3 mixing ratios to a statistical classification of BB events, which is based on OA composition. We found increased CO and O3 levels during medium and high BB influence during the intensive campaign. A backward trajectory analysis confirmed different source regions for the identified periods based on the OA cluster. Typically, cleaner air masses arrived from northeast, i.e., mainland China and Yellow sea during the intensive campaign. 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. These findings highlight that BB activities in Northern Southeast Asia significantly enhances the regional OA loading, chemical PM2.5 composition and the trace gases in northwestern Vietnam. The presented analysis adds valuable data on air quality in a region of scarce data availability.
 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).
 Nguyen, D. L, et al. Carbonaceous aerosol composition in air masses influenced by large-scale biomass burning: a case-study in Northwestern Vietnam. ACPD., https://doi.org/10.5194/acp-2020-1027, in review, 2020.
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.: Trace gases and organic aerosol at a rural site in Vietnam during large scale biomass burning, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-181, https://doi.org/10.5194/egusphere-egu21-181, 2020.
The identification of the severe COVID-19 virus in December 2019 led the World Health Organization to declare a global pandemic by March 2020. Up till recently with the first available vaccines, the only prevention measures include strict social, travel and working restrictions in a so-called lockdown period that lasted for several weeks (mid-March to the end of April 2020 for most of Europe). This abrupt change in social behaviour is expected to impact local but also regional atmospheric composition, and the environmental impact is highly interesting to study.
The Aerosol, Clouds and Trace Gases Research Infrastructure (ACTRIS) is a pan-European research infrastructure producing high-quality data and information on short-lived atmospheric constituents and on the processes leading to the variability of these constituents in natural and controlled atmospheres. ACTRIS integrates, harmonizes, and distributes datasets, activities, and services provided by the Central Facilities and National Facilities, located in 22 European countries.
During the lockdown period in spring 2020 most of the ACTRIS observational were operational. The National Facilities performing the ambient measurements are generally regional background sites, with the aim to detect changes on regional level. Within the context of the current COVID-19 outbreak, ACTRIS has been continuously providing access to data on air quality and atmospheric composition. This is of particular interest and importance as it provides unique information measured from the ground to assess the European air quality and atmospheric composition during the lockdown complementing, in a fundamental way, satellite observations and modelling analysis.
ACTRIS released a comprehensive and quality assured set of atmospheric measurement data during the COVID-19 pandemic spring 2020 – January– May 2020. This includes:
- - 30 sites with aerosol in situ measurements providing mainly absorption and scattering coefficient, size and/or number distribution. A few sites with high time solution aerosol chemical composition;
- - 12 sites with trace gases in situ data providing VOCs and NOX measurements;24 sites with aerosol remote sensing data providing profiles with backscattering and extinction coefficient;
- - 11 cloud remote sensing sites providing profile information of 9 various cloud properties.
To facilitate studies, ACTRIS has compiled the data and coined a DOI for the data sets measured during the COVID-19 spring lockdown period, including an intensive aerosol remote sensing campaign in May. This presentation will present the data set and the potential applications and benefits using ACTRIS COVID-19 dataset for studying atmospheric composition changes during COVID-19 lockdown periods.
How to cite: Saponaro, G., Lund Myhre, C., Fiebig, M., O'Connor, E., Mona, L., Pascal, N., and Laj, P.: An overview of ACTRIS observational data in relation to the 2020 lockdown period in Europe, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-8645, https://doi.org/10.5194/egusphere-egu21-8645, 2021.
Present research contributes to scientific knowledge concerning spatial and temporal variation of major air pollutants with high resolution at the country scale bringing statistical information on concentrations of NOx, O3, CO, SO2 and particulate matter with an aerodynamic diameter below 10 μm (PM10) and below 2.5 μm (PM2.5) during the pandemic year 2020 using an observational data set from the Romanian National Air Quality Network in seven selected cities spread out over the country. These cities have different level of development, play regional roles, might have potential influence at European scale and they are expected to be impacted by different pollution sources. Among them, three cities (Bucharest, Brașov, Iași) appear frequently on the list of the European Commission with reference to the infringement procedure that the European Commission launched against Romania in the period 2007-2020 regarding air quality.
Air pollutant data was complemented with local meteorological parameters at each site (atmospheric pressure, relative humidity, temperature, global solar radiation, wind speed and direction). Statistics of air pollutants provide us with an overview of air pollution in main Romanian cities. Correlations between meteorological parameters and ambient pollutant levels were analyzed. Lowest air pollution levels were measured during the lockdown period in spring, as main traffic and non-essential activities were severely restricted. Among exceptions were the construction activities that were not interrupted. During 2020, some of selected cities experienced few pollution episodes which were due to dust transport from Sahara desert. However, in Bucharest metropolitan area, some cases with high pollution level were found correlated with local anthropogenic activity namely, waste incinerations. Air mass origins were investigated for 72 hours back by computing the air mass backward trajectories using the HYSPLIT model. Dust load and spatial distribution of the aerosol optical depth with BSC-DREAM8b v2.0 and NMBM/BSC-Dust models showed the area with dust particles transport during the dust events.
The obtained results are important for investigations of sources of air pollution and for modeling of air quality.
The research leading to these results has received funding from the NO Grants 2014-2021, under Project contract no. 31/2020, EEA-RO-NO-2019-0423 project. NOAA Air Resources Laboratory for HYSPLIT transport model, available at READY website https://www.ready.noaa.gov and the Barcelona dust forecast center for BSC-DREAM8b and NMBM/BSC-Dust models, available at: https://ess.bsc.es/bsc-dust-daily-forecast are also acknowledged. The data regarding ground-based air pollution and meteorology by site was extracted from the public available Romanian National Air Quality Database, www.calitateaer.ro.
How to cite: Iorga, G. and Burghelea, G.-B.: Changes of air pollutants’ concentrations in selected Romanian cities during the pandemic year 2020, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-1800, https://doi.org/10.5194/egusphere-egu21-1800, 2021.
In 2020, the COVID-19 pandemic imposed countries to apply stringent policies to slow down the spread of the SARS-CoV-2 virus. During the Spring time, most countries had announced a national lockdown that had important consequences on many capital cities such as Mexico City and Paris. The shutdown of many of these economic activities had a direct impact on the traffic sector. Travel restrictions led to a drastic decrease of major air pollutants in those two cities. From each local air quality monitoring network, we discriminated background, urban and traffic sites. By looking at the differences between urban sites versus background sites, we observed in Mexico City a decrease of 51%, 58 % and 44 % for ΔNOx, ΔCO2 and ΔCO concentrations, respectively, during the lockdown. Markedly, their concentrations remained below typical levels after the end of the lockdown until September. Then, from September to the end of the year, the pollutants concentrations increased back to the same level as before the lockdown. The same behavior was seen at Paris. During the spring lockdown period, we observed a decrease of 72 %, 70 % and 88 % for ΔNOx, ΔCO2 and ΔCO concentrations, respectively. Until the end of the summer, the concentrations of those pollutants remained at the same level as during the lockdown. From September, we observed an increase of pollutants concentrations to the levels of previous years.
Despite road traffic increases by the end of the lockdown in both megacities, the remainly low concentrations seen for those pollutants until September might be an effect of the atmospheric dispersion combined with a slow reactivation of anthropogenic activities. Nevertheless, a second lockdown period imposed in France (from Oct. 30 to Dec. 15) have clearly not shown the same impact on pollutant concentrations as the first one exhibited. On the contrary, no significant changes in pollutant concentrations were observed during the second lockdown, and moreover, peaks of ΔNOx, ΔCO2 and ΔCO concentrations were seen during the last weekends of the lockdown of up to 32 % of increase, compared to the weekday-level during the 2nd lockdown. This can be explained by less stringent travel restrictions combined with pre-Christmas preparations in Paris.
How to cite: Tran, S., Ramonet, M., Lauvaux, T., Ciais, P., Laurent, O., Hernández-Paniagua, I. Y., González del Castillo, E., and Grutter, M.: Impacts of COVID-19 lockdown strategies on NOx, CO and CO2 surface observations on two megacities: focus on the traffic sector in Mexico City (Mexico) and Paris (France), EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-14272, https://doi.org/10.5194/egusphere-egu21-14272, 2021.
Governments worldwide have used non pharmaceutical interventions known as lockdowns to contain the spread of the coronavirus pandemic, leading to a mass reduction in road traffic and international travel as working from home becomes the new normal. As a result, primary emissions of nitrogen oxides are expected to have largely decreased. A study of the UK’s first lockdown (Lee et al. 2020) used historical averages, taken between 2015 and 2019, as a baseline for comparison. This method is simplistic however does not fully account for the year to year meteorological variation. The UK’s first national lockdown was announced on 23rd March 2020 extending to 31st May 2020 and by mid-April traffic was reduced by 70% compared to normal according to the Department for Transport. We examined NO2 and O3, measured by the UK’s Automatic Urban and Rural Network for the year 2020 consisting of 65 urban traffic and 61 urban background sites, for the lockdown period from 2000 to 2020. Between 2000 and 2019 NO2 decreased by an average of 0.88 and 0.49 μg m-3 per year at urban traffic and urban background sites respectively. In 2020, the lockdown caused a 20 μg m-3 decrease in NO2 at urban traffic sites, an equivalent of 26 years at the previous rate.
To improve on the previous method, we have constructed random forest models to simulate business as usual NO2 and O3 concentrations at AURN sites in 9 cities, allowing changes in meteorology to be fully accounted for. These simulations were then compared to lockdown measurements in 2020. We observed an average 55% decrease in NO2 however O3 concentrations were elevated with an average 29% increase. The total oxidant, Ox, (sum of NO2 and O3) experienced marginal change (< 1%) indicating the changes in NO2 and O3 were largely due to photochemical repartitioning. This has highlighted the importance of O3 in urban locations in a future low NOx environment in the UK when electric vehicle fleets are adopted.
Lee et al., Atmos. Chem. Phys., 2020, 20, 15743 – 15759
How to cite: Evans, R., Lee, J., and Drysdale, W.: Changes in surface level NO2 in the UK during the COVID-19 pandemic compared to predicted 2020 concentrations and the impact on O3., EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-8359, https://doi.org/10.5194/egusphere-egu21-8359, 2021.
An analysis of the CO and CH4 total column (TC) as well as aerosol optical depth (AOD) data in background and urban Eurasian regions for different time-periods and seasons from 1998 to 2018 years is presented. Trend estimates based on long-term spectroscopic datasets of OIAP RAS for Moscow, Zvenigorod (ZSS, Moscow province), Beijing (joint site of OIAP RAS and IAP CAS) and NDACC stations located in Eurasia are compared between themselves and with similar assessments obtained from satellite data. The comparison of satellite and ground-based trend estimates was provided for the days of synchronous measurements only. Analysis results of the satellite observations of AIRS v6 of CO and CH4 TC and MODIS AOD data are confirmed by ground-based trend estimates. Significant decrease of anthropogenic CO in the megacities Moscow (2.9±0.6%/yr) and Beijing (1.2±0.2%/yr) for autumn months of 1998−2018 was found according to ground-based spectroscopic observations. In spite of total anthropogenic CO emission decrease (for Europe and China) and the decrease of wild-fires emissions in Central North Eurasia (0−90° E, 42−75° N) in 2008−2018 we found CO TC stabilization or even its increase in background regions of Northern Eurasia in summer and autumn months of 2008−2018. Decrease of AOD over Central and Southern Europe as well as over China (1−5%/yr) was observed since 2007. Since 2007-2008 an increase in CH4 TC positive trend values over Northern Europe as well as for tropical belt of Eurasia was obtained.
Additionally some results of comparison of orbital (AIRS, MODIS, TROPOMI) and ground-based spectroscopic diurnal and 10-days averaged data are presented.
This work was supported by the Russian Science Foundation under grant № 20-17-00200 (analysis orbital information and trend distributions).
How to cite: Rakitina, A., Skorokhod, A., Pankratova, N., Shtabkin, Y., Wang, G., and Vasilieva, A.: Recent changes of atmospheric composition in background and urban Eurasian regions, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-2532, https://doi.org/10.5194/egusphere-egu21-2532, 2021.
Over last two decades, South Asia has witnessed a rapid increase in population, industrialization, and energy demands. Consequently, 2-6 fold increase in the emission of particulate matter (PM) and trace gases were reported. Air pollution in South Asia has more adverse impact and is linked to nearly 1 million premature deaths and around 10 million tonnes of crop loss in a year. So, monitoring of trace gases and PM concentrations over urban centers has received significant attention among scientists, policymakers, health regulatory agencies, and the media. Particularly over the Indian region, this becomes significant, as the observation of trace gases and PM concentrations with fairly good temporal and spatial resolutions is limited. Concerns about air quality and transport pathways on a regional scale also place more stringent demand on observations and modeling effort. Quantifying the source contribution (regional emission due to various anthropogenic activities such as city traffic density vs. long-range transport due to meteorological influence) of trace gases and PM over different temporal and spatial scales has been receiving significant attention. In view of this, measurement of trace gases and PM in concurrence with meteorological variables (wind speed and direction) is of paramount importance.
In this study, we have presented three-year surface measurements of TGs (O3, CO, NOx, SO2 and NH3) and PMs (PM2.5 and PM10) at three coastal and urban sites, namely, Trivandrum (TVM, 8.5°N, 76.9°E, 5m AMSL), Chennai (CHN, 13.7°N, 80.2°E, 6.7m AMSL) and Bhubaneswar (BHB, 20.2°N, 85.8°E, 45m AMSL) located in India. -In addition to that Ozone Monitoring Instrument OMI’s, surface mass concentration data for SO2 and Moderate Resolution Imaging Spectroradiometer (MODIS) fire counts data were also used to identify potential sources. The principal component analysis (PCA) and concentrated weighted trajectories (CWT) were applied to the dataset. The TGs and PM showed high values during winter and lower values in a monsoon at these sites. Both TGs and PM values were higher at BHB compared to those at TVM and CHN. Surface O3 at BHB was about 3 times higher than that at TVM and 2.2 times higher than that at CHN. Interestingly, PCA suggests that the major concentrations of O3, PM10, and SO2 at TVM and CHN were transported from different locations and not produced locally except for pre-monsoon at CHN, which was of local origin. CWT analysis and OMI’s surface mass concentration data also suggest that the air quality at TVM could be influenced by heavy emissions transported from the Indo-Gangetic plain. The Merra-2 reanalysis well captured seasonal variations of TGs and PMs; and it overestimated surface O3, by a factor of about 2 to the measurement at the study sites.
How to cite: Chhari, A., Dhadwal, V. K., Sahu, L. K., Madhavan, B. L., Das, T., Ramasamy, B., Kumar, P., Pk, B., Chakravorty, A., Raju, P. L. N., and Sinha, P. R.: Source apportionment of surface-level trace gases and particulate matter at three tropical coastal sites in India, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-14152, https://doi.org/10.5194/egusphere-egu21-14152, 2021.
We use the OMI-QA4ECV-v1.1 NO2 tropospheric columns over the 10-yr 2008-2017 period to confront satellite-based trends in NO2 concentrations to those from the state-of-the-art regional chemistry-transport model CHIMERE and to evaluate the bottom-up anthropogenic and biogenic NOx emissions in Europe. A focus is made for the 30 most populated urban areas in Europe. Over urban areas in Western Europe, except for coastal cities, OMI confirm the drop in the simulated CHIMERE NO2 tropospheric columns based on the latest country emission official reporting. OMI does not show significant decreasing trends over Central and Eastern Europe urban areas. Increasing biogenic emissions helps reconciling CHIMERE and OMI trends over urban areas in Central Europe and over rural areas, confirming the importance of accounting for non-anthropogenic emissions to assess long-term trends. Over Eastern Europe, our results question emission reductions estimated for particular sectors and in particular the road transport, public power and industrial emissions.
How to cite: Fortems-Cheiney, A., Broquet, G., Pison, I., Saunois, M., Potier, E., Berchet, A., Dufour, G., Siour, G., Denier van der Gon, H., Dellaert, S., and Boersma, F.: Analysis of the anthropogenic and biogenic NOx emissions over 2008-2017: assessment of the trends in the 30 most populated urban areas in Europe, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-4566, https://doi.org/10.5194/egusphere-egu21-4566, 2021.
Peroxyacetyl nitrate (CH3C(O)O2NO2; abbreviated as PAN) is the main tropospheric reservoir of nitrogen oxide radicals (NOx) and contributes to redistributing NOx from source to remote regions. Recently, PAN total columns have been retrieved from the radiance spectra recorded by IASI (Infrared Atmospheric Sounding Interferometer) onboard the Metop satellite platforms, using a neural network-based retrieval approach. The daily global distributions obtained from these measurements provide a comprehensive picture of PAN through the troposphere.
Here we exploit as a climatology the 13-year time series of global PAN measurements derived from the IASI/Metop-A observations (October 2007 - December 2020) to characterize the spatial distribution and seasonal variability of PAN abundance worldwide. In particular, continental areas within the tropics appear to be source regions of PAN throughout the year, whereas PAN at North Hemisphere mid- and high latitudes exhibits a more pronounced seasonal cycle and peaks during the boreal summer. Strong outflows of PAN are captured over the oceans, downwind of continental source regions such as Eastern Asia and Eastern US. This dataset also allows us to investigate the recent trends of atmospheric PAN abundance over the last 13 years, over both source and remote areas.
To better understand what drives the spatial distribution and variability of PAN, we analyze alongside the regional time series of PAN those of carbon monoxide (CO) from IASI/Metop-A, and of formaldehyde (HCHO) and nitrogen dioxide (NO2) from OMI/Aura (Ozone Monitoring Instrument). Locally, we find simultaneous enhancements of PAN and CO abundances, which in this case indicates that most PAN originates from fire-derived precursors. This mainly occurs over the typical biomass burning regions in the tropics. Overall, strong correlations are observed over source areas between PAN and HCHO, which is used here as a tracer of tropospheric chemistry and of the presence of oxygenated volatile organic compounds (OVOCs), while there is no particular correlation with NO2. The preliminary results suggest that PAN distribution and seasonality is primarily driven by the availability in OVOCs, and hence in peroxyacetyl radical, and that a locally weak NO2 abundance does not prevent the formation of PAN.
How to cite: Franco, B., Clarisse, L., Clerbaux, C., and Coheur, P.-F.: Analysis of space-based observations of peroxyacetyl nitrate (PAN) and its relation to other atmospheric tracers, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-9224, https://doi.org/10.5194/egusphere-egu21-9224, 2021.
Reactive nitrogen in the upper troposphere (~8-12 km) impacts global climate, air quality and the oxidizing capacity of the whole troposphere. Here we use aircraft observations from instruments onboard the NASA DC8 aircraft for campaigns from 1997 (SONEX) to the recent ATom campaign (2016-2018) and the MOZAIC commercial aircraft campaign (2003-2005) to address uncertainties in the dynamics of reactive nitrogen (NOy = NOx + NOx reservoir compounds) in the global upper troposphere (UT). Our initial analysis of the DC8 aircraft observations is consistent with previous work in that PAN is the dominant NOy component (average: 43%; range: 40-60%), followed by NOx (on average, 21%), with smaller contributions (on average, 3.5-12.5%) from pernitric acid (HNO4), organonitrate (RONO2) and nitric acid (HNO3). We go on to compare multiyear mean NOy from MOZAIC to the combination of all NASA DC8 campaigns to determine whether we can build a near-global climatology of NOy and its components to compare to GEOS-Chem to assess our understanding of these very important atmospheric components.
How to cite: Wei, N., Marais, E. A., Wennberg, P. O., Allen, H. M., Crounse, J. D., Blake, D. R., Neuman, A. J., Huey, G. L., Veres, P. R., Thompson, C. R., Bourgeois, L., Peischi, J., and Sauvage, B.: Reactive nitrogen in the global upper troposphere from NASA DC8 and MOZAIC aircraft campaigns, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-10085, https://doi.org/10.5194/egusphere-egu21-10085, 2021.
Volatile organic compounds (VOCs) are key precursors for the formation of surface level ozone (O3) and secondary organic aerosols, and therefore, they have a significant impact on air quality and climate. In addition, through their interaction with the hydroxyl radical (OH), they impact the atmospheric lifetime of methane, further affecting climate. Among non-methane VOCs, the oxygenated species (OVOCs) are especially relevant in remote regions where they constitute the largest OH sink. Due to the paucity of data at these locations, OVOCs sources and sinks are poorly constrained in models. This work addresses the critical need for OVOC observations at remote locations. A high-sensitivity quadrupole-based proton-transfer-reaction mass-spectrometry VOC analyzer (hs-PTR-MS) was deployed at La Réunion --- a remote tropical island located in the south west Indian Ocean, home to the Maïdo observatory --- between October 2017 and November 2019. As the observatory is located near the top of the planetary boundary layer (PBL), pristine marine boundary layer air masses, enriched with compounds emitted by mesoscale sources, reach the observatory during the day. At night, the observatory is located in the free troposphere. The variability in PBL development drives the diel concentration profiles of a variety of biogenic and anthropogenic tracers recorded with the hs-PTR-MS instrument. The seasonal variability of biogenic tracers is driven by the hot and wet versus the cold and dry seasons. Every year, biomass burning plumes originating from African and Madagascan fires reach the observatory between August and November, significantly impacting local air quality at La Réunion.
We will present both the diel and seasonal variability using the 2-year near-continuous (O)VOC dataset recorded with the hs-PTR-MS instrument. The analysis of the complete dataset is performed using the positive matrix factorization approach, complemented by back-trajectory calculations using the Lagrangian transport model FLEXPART-AROME to identify mesoscale sources.
How to cite: Verreyken, B., Amelynck, C., Schoon, N., Müller, J.-F., Brioude, J., Kumps, N., Hermans, C., Metzger, J.-M., and Stavrakou, T.: Diurnal and seasonal variability in VOC composition at the remote tropical high-altitude Maïdo observatory (21.1°S, 54.4°E, 2160 m altitude), EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-3192, https://doi.org/10.5194/egusphere-egu21-3192, 2021.
Volatile Organic Compounds (VOCs) have direct influences on air quality and climate. They also play a key role in atmospheric chemistry, as they are precursors of secondary pollutants, such as ozone (O3) and secondary organic aerosols (SOA).
Long-term datasets of in-situ atmospheric measurements are crucial to characterize the variability of atmospheric chemical composition. Online and continuous measurements of O3, NOx and aerosols have been achieved at the SIRTA-ACTRIS facility (Paris region, France), since 2012. Regarding VOCs, they have been measured there for several years thanks to bi-weekly samplings followed by offline Gas Chromatography analysis. However, this method doesn’t provide a good representation of the temporal variability of VOC concentrations. To tackle this issue, online VOC measurements using a Proton-Transfer-Reaction Quadrupole Mass-Spectrometer (PTR-Q-MS) have been started in January 2020.
The dataset acquired during the first year of online VOC measurements is analyzed, which gives insights on VOC seasonal variability. The additional long-term datasets obtained from co-located measurements (O3, NOx, aerosol physical and chemical properties, meteorological parameters) are also used for the sake of this study.
Due to Covid-19 pandemic, the year 2020 notably comprised a total lockdown in France in Spring, and a lighter one in Autumn. Therefore, a focus can be made on the impact of these lockdowns on the VOC variability and sources. To this end, the diurnal cycles of VOCs considered markers for anthropogenic sources are carefully investigated. Results notably indicate that markers for traffic and wood burning sources behave quite differently during the Spring lockdown in comparison to the other periods. A source apportionment analysis using positive matrix factorization allows to further document the seasonal variability of VOC sources and the impacts on air quality associated with the lockdown measures.
How to cite: Simon, L., Gros, V., Petit, J.-E., Truong, F., Sarda-Esteve, R., Baisnee, D., Bonnaire, N., Dupont, J.-C., Haeffelin, M., Marchand, C., and Favez, O.: First year of real-time VOC measurements at the SIRTA facility (Paris region, France): diurnal and seasonal variabilities, impact of lockdowns on air quality, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-8643, https://doi.org/10.5194/egusphere-egu21-8643, 2021.
Complex analysis of CO total content measurements in Moscow (site OIAP, city center) and Moscow province (site ZSS, Zvenigorod Scientific Station) using OIAP RAS spectroscopic data, MosEcoMonitoring automatic network station (MEM) data and satellite monitoring results. Analysis of meteorological information on parameters of atmospheric boundary layer (ABL) in Moscow and surrounding regions is performed. Long-term variability and trends of CO total column (TC) and meteorological parameters was explored, pollutant accumulation characteristics of carbon monoxide in calm days in ABL were obtained. ZSS data as regional background characteristics were used. It was revealed that transports from Moscow don’t lead to a significant increase in CO TC in the ZSS. The decrease of CO TC averaged annual values for 2000−2018 in Moscow (-2.56±0.52%/yr) and ZSS (-1.15±0.37%/yr) is established. After approximately 2007−2008 the rate of CO TC decrease declined at both sites. In the summer and autumn months of 2008-2018 CO TC increase with the rate of about 0.7%/yr is found at the ZSS. Increase of wind velocity in Moscow ABL in different periods of 2000-2018 (0.4-1.6%/yr) is established. In contrast with Moscow, statistically significant changes of wind velocity in Kaluga province were not detected. Repeatability of calm days in Moscow for 2006−2017 time-period was decreased (-7.06±3.96%/yr) with the diminution of anthropogenic part of the CO content in the same period (-6.72±3.48%/yr). Obtained results indicate not only urban anthropogenic emissions reduction but also the influence of climatic (meteorological) factor on Moscow air quality.
How to cite: Kirillova, N., Rakitin, V., Skorokhod, A., Rakitina, A., and Shilkin, A.: Carbon monoxide variability in the atmosphere of Moscow region., EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-8351, https://doi.org/10.5194/egusphere-egu21-8351, 2021.
As the production of ozone in surface air is determined by ambient temperature and by the prevalent chemical regime, a very different temperature dependence of ozone production emerges for nitrogen oxides (NOx) and volatile organic compounds (VOC) limited regions. In this study we evaluated the temperature sensitivity of ozone production for rural, suburban as well as urban sites in Austria on seasonal basis. The analysis is based on 30 years of observational data from Austrian monitoring networks for the time period 1990 – 2019. Reductions in precursor emissions as observed in 2020 in Austria due to the pandemic will be used to test the obtained results. Surface ozone, NOx, daily sums of global radiation and minimum daily temperature are used as covariates in our study. The observed NOx to VOC ratio at individual sites is variable over time due to changes in precursor emissions and/or the variability of meteorological parameters such as mixing layer height. At the site level we relate the temperature sensitivity of ozone production to the daily mean NOx mixing ratio and the daily minimum temperature. This information allows us to determine the impact of past/future temperature changes on surface ozone abundance in the context of reductions of NOx emissions and changing methane backgrounds.
How to cite: Stähle, C., Mayer, M., Schmidt, C., Kult, J., Klaus, V., Trimmel, H., Schreier, S., Karlicky, J., Alexander, M., and Rieder, H.: 30 years of surface ozone measurements in Austria: long-term trends, attainment statistics, and changes in the temperature sensitivity of surface ozone production, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-11467, https://doi.org/10.5194/egusphere-egu21-11467, 2021.
Tropospheric ozone (O3) is a critical pollutant over the Mediterranean countries, including Portugal, due to systematic exceedances to the thresholds for the protection of human health. Due to the location of Portugal, on the Atlantic coast at the south-west point of Europe, the observed O3 concentrations are very much influenced not only by local and regional production but also by northern mid-latitudes background concentrations. Ozone trends in the Iberian Peninsula were previously analysed by Monteiro et al. (2012), based on 10-years of O3 observations. Nevertheless, only two of the eleven background monitoring stations analysed in that study are located in Portugal and these two stations are located in Porto and Lisbon urban areas. Although during pollution events O3 levels in urban areas may be high enough to affect human health, the highest concentrations are found in rural locations downwind from the urban and industrialized areas, rather than in cities. This happens because close to the sources (e.g., in urban areas) freshly emitted NO locally scavenges O3. A long-term study of the spatial and temporal variability and trends of the ozone concentrations over Portugal is missing, aiming to answer the following questions:
- What is the temporal variability of ozone concentrations?
- Which trends can we find in observations?
- How were the ozone spring maxima concentrations affected by the COVID-19 lockdown during spring 2020?
In this presentation, these questions will be answered based on the statistical analysis of O3 concentrations recorded within the national air quality monitoring network between 2005 and 2020 (16 years). The variability of the surface ozone concentrations over Portugal, on the timescales from diurnal to annual, will be presented and discussed, taking into account the physical and chemical processes that control that variability. Using the TheilSen function from the OpenAir package for R (Carslaw and Ropkins 2012), which quantifies monotonic trends and calculates the associated p-value through bootstrap simulations, O3 concentration long-term trends will be estimated for the different regions and environments (e.g., rural, urban). Moreover, taking advantage of the unique situation provided by the COVID-19 lockdown during spring 2020, when the government imposed mandatory confinement and citizens movement restriction, leading to a reduction in traffic-related atmospheric emissions, the role of these emissions on ozone levels during the spring period will be studied and presented.
Carslaw and Ropkins, 2012. Openair—an R package for air quality data analysis. Environ. Model. Softw. 27-28,52-61. https://doi.org/10.1016/j.envsoft.2011.09.008
Monteiro et al., 2012. Trends in ozone concentrations in the Iberian Peninsula by quantile regression and clustering. Atmos. Environ. 56, 184-193. https://doi.org/10.1016/j.atmosenv.2012.03.069
How to cite: Gama, C., Monteiro, A., Lopes, M., and Miranda, A. I.: Temporal patterns and trends of surface ozone concentrations over Portugal, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-5119, https://doi.org/10.5194/egusphere-egu21-5119, 2021.
Near-surface ozone is a harmful air pollutant, which is not only controlled by chemical production and loss processes. The major removal process of near-surface ozone is dry deposition accounting for 20 % of the total tropospheric ozone loss. Due to its significance, parameterizations used in atmospheric chemistry models represent a major source of uncertainty for tropospheric ozone simulations. This uncertainty might be one of the reasons why global models tend to overestimate ozone, when compared to observations. The model used in this study, the global atmospheric model ECHAM5/MESSy (EMAC), is no exception. Like most global models, EMAC employs a “resistances in series” scheme, which is hardly sensitive to local meteorological conditions (e.g. humidity) and lacks non-stomatal deposition. In this study, these missing features have been implemented in EMAC affecting not only the deposition of ozone but also the removal of ozone precursors, resulting in lower chemical production of ozone.
Furthermore, near-surface ozone may be significantly impacted by water vapour forming complexes with peroxy radicals. The role of water in the reaction of HO2 radical with itself and nitrogen oxides is known from the literature. However, in current models only the former is considered by assuming a linear dependence on water concentrations. Recent experimental evidence for the significant role of water on the kinetics of one of the most important reaction for ozone chemistry, namely NO2 + OH, has been published. Here, the available kinetic data for the HOx + NOx reactions have been critically re-assessed and included in EMAC to test its global significance. Additionally, we considered the representation of isoprene and nitrous acid (HONO) as important oxidants for lower tropospheric chemistry. Namely, for isoprene emissions we added a drought stress factor which enables a higher sensitivity to meteorology leading to reduced emissions. Also, we firstly implemented soil emissions of HONO which is known as a missing source in models. The implications of these modifications on the global tropospheric composition are analysed, focusing on near-surface ozone and related precursors. The improved representation of ozone in EMAC is demonstrated using measurements from the Infrared Atmospheric Sounding Interferometers (IASI), the Tropospheric Ozone Assessment Report (TOAR) database and from the Trajectory-mapped Ozonesonde dataset for the Stratosphere and Troposphere (TOST). The overall changes might help to reduce the uncertainty and overestimation of models predicting near-surface ozone.
How to cite: Emmerichs, T., Franco, B., Wespes, C., Rosanka, S., and Taraborrelli, D.: Unravelling the ozone-weather relationship: the role of vegetation and radical reactions, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-8916, https://doi.org/10.5194/egusphere-egu21-8916, 2021.
The chemical composition of rainwater is an indicator of the air quality and sources of influence. In this study, pH and ionic concentrations were measured in rain samples collected during monsoon season of 2018 at a rural agricultural site located in northern part of India. Wet deposition fluxes of reactive nitrogen species NH4+ over NO3- were calculated to estimate their annual deposition. The pH of samples varied between 5.2 and 6.14, with an average value of 5.72 which is in alkaline range considering 5.6 as the neutral pH of cloud water with atmospheric CO2 equilibrium. These relatively high pH values indicate the neutralisation of acidity in precipitation. Samples were analysed for their cationic and anionic content using ion chromatography. The results showed that NH4+ concentrations were higher than NO3- with the VWM concentrations of 187.23 μeql-1 and 26.79 μeql-1 respectively. Furthermore, wet deposition flux of NH4+-N was calculated as 4.25 kg ha-1 yr-1 while that of NO3--N was as 2.10 kg ha-1 yr-1. VWM concentrations of major ions decreased in the following order NH4+ > Ca2+ > SO42- > NO3- > K+ > Cl- > Na+ > Mg2+. In this study, relatively high NH4+ concentrations in rainwater can be attributed to nearby agricultural activities, excreta and biomass burning.
Keywords: Rainwater, Neutralisation, VWM concentration, Agricultural site, Reactive Nitrogen.
How to cite: Yadav, S. and Kulshrestha, U.: Wet Deposition Fluxes of Nitrate and Ammonium at a Rural Agricultural Site in north India, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-9103, https://doi.org/10.5194/egusphere-egu21-9103, 2021.
Goal of Study: The study focuses on the application of developed spatial interpolation method  to assessment of atmospheric pollutant deposition fluxes. This case study was done for estimating the total ammonium wet deposition in the Eastern Siberia region of Russia.
Data: Measurement data for 2017 on the ammonium concentration in atmospheric precipitation were obtained from the stations within the Baikal natural preserved territory thanks to the international EANET network  and the Russian national network of precipitation chemistry (PCnet) operated by Roshydromet.
Method: On the first step of the algorithm, we prepare the point data on the concentration of from the measurements of PCnet stations in the region. On the second step, we interpolate the precipitation chemistry data to the meteorological stations located in the study region followed by calculation of deposition fluxes at all these sites. The values obtained are interpolated for the regular grid of 100-km by 100-km cells within region. Finally, the total pollutant wet deposition for whole region is a sum of deposition fluxes calculated for each cell.
Results: We calculated the weighted-average annual concentration (WAC) of ammonium in atmospheric precipitation at 7 stations of EANET and PCnet in the region. We interpolated the WAC data on the grid cells in the Lake Baikal preserved territory (BPT). The variation of ammonium WAC throughout the BPT is 0.9 mg/l (south of the region) to 0.1 mg/l (northwestern part) with average value of 0.34 mg/l for the whole region.
Based on the WAC data and the obtained precipitation amounts at 23 meteorological stations within BPT, we calculated the deposition fluxes for network of more spatial density combined of PC and meteorological stations.
Using the “point” calculation results, we have constructed a two-dimensional spatial interpolation of wet ammonium fluxes per each cell. According to the study results, the total amount of ammonium felt with precipitation out from the atmosphere in the territory around Lake Baikal is 42 thou. ton per year. The value of average deposition per cell of 100x100 km for BPT region is 666 ton while in the surround of the EANET station Listvyanka (west Baikal shore) is 828 ton. The spatial distribution of wet annual ammonium deposition is presented at the map of the region.
This study was carried out in the framework of the Research Projects АААА-А20-120013190049-4 «Development of methods and technologies for monitoring of environmental pollution under the influence of transboundary pollutants transport (UNECE: EMEP, ICP IM) and acid deposition in East Asia (EANET)» and АААА-А20-120020490070-3 «Development and improvement of methods and technologies for integrated background monitoring and comprehensive assessment of the environmental state and pollution in the Russian Federation including their dynamics»
1. Gromov S. A., Galushin D. A., Zhadanovskaya E. A. 2020. Estimation of the total wet sulfur and nitrogen deposition as a part of pollution balance in the south of the Russian Far East based on the monitoring data. - Geophysical Research Abstracts, EGU2020-13871, EGU General Assembly.
2. The Acid Deposition Monitoring Network in East Asia (EANET)- URL: https://www.eanet.asia/
How to cite: Gromov, S. A., Galushin, D. A., and Zhadanovskaya, E. A.: An assessment of the total wet ammonium deposition in the East Siberia of Russia based on monitoring data, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-13642, https://doi.org/10.5194/egusphere-egu21-13642, 2021.
The purpose of our research was to evaluate spatial and temporal variations of major acidifying compounds in precipitation. Sulfur (from sulfates), Nitrogen (Dissolved Inorganic Nitrogen), and other major ions. Wet deposition data from three stations of the Russian EANET region was processed and analyzed. The period under investigation is framed from 2007 to 2019.
Mondy station (51.4 ° N, 101.0 ° E) is located on Mount Chasovye Sopki (plateau between the Eastern Sayan and Khamar-Daban mountain ranges) at an altitude of 2005 meters above sea level. Yailu station (51.5 ° N, 87.4 ° E) is located at the spurs of the Abakan range on the shore of Lake Teletskoye at an altitude of 491 meters above sea level. Primorskaya station (43.4° N; 132.1° E) is located on the western slope of a branch of the Southern Sikhote-Aline Ridge, in the valley of Komarovka river at an altitude of 85 meters above sea level. Yailu station is operated under a Russian integrated background monitoring network, while Mondy and Primorskaya sites are included in EANET.
For evaluation of temporal variations, Mann-Kendall Test and Sen's Slope estimation were applied to check the statistical significance of seasonal and year trends and speed of changes in wet depositions and average weighted concentrations. For calculations, R-statistics and MAKESENS were used. For Mondy station, statistically significant trends at the level over 95% were found for non-sea-salt sulfur and potassium average weighted mean concentrations (with the negative slope approximately 28% and 16 % respectively) and at the level from 90 to 95 % for ammonium nitrogen and conductivity. There was no linear trend found at this station for total wet depositions. At the same time for Komarovka station, statistically significant linear trends were found in average weighted concentrations and wet deposition for magnesium and hydrogen at the level over 95%. For Yailu station, slightly increasing linear trend with the significance of over 90% was found for non-sea-salt sulfate and calcium weighted mean concentrations. And for ammonium nitrogen and calcium wet deposition – with significance over 95%.
This study was carried out in the framework of the Research Project АААА-А20- 120013190049-4 «Development of methods and technologies for monitoring of environmental pollution under the influence of transboundary pollutants transport (UNECE: EMEP, ICP IM) and acid deposition in East Asia (EANET)»
How to cite: Konkova, E. S., Zhigacheva, E. S., and Gromov, S. A.: Sulfur and Nitrogen Wet Deposition trends at three background monitoring stations of the Russian EANET region., EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-14227, https://doi.org/10.5194/egusphere-egu21-14227, 2021.
Carbonyl sulfide (OCS) is the most abundant sulfur containing gas in the atmosphere and is an important source of stratospheric aerosol. Furthermore, it has been shown that OCS can be used as a proxy for photosynthesis, which is a powerful tool in quantifying global gross primary production. While considerable improvements have been made in our understanding of the location and magnitude of OCS fluxes over the past few decades, recent studies highlight the need for a new satellite dataset to help reduce the uncertainties in current estimations. The Infrared Atmospheric Sounding Interferometer (IASI) instruments on-board the MetOp satellites offer over 14 years of nadir viewing radiance measurements with excellent spatial coverage. Given that there are currently three IASI instruments in operation, there is the potential for a significantly larger OCS dataset than is currently available elsewhere. Retrievals of OCS from these IASI radiances have been made using an adapted version of the University of Leicester IASI Retrieval Scheme (ULIRS). OCS total column amounts are calculated from profiles retrieved on a 31-layer equidistant pressure grid, using an optimal estimation approach for microwindows in the range 2000 – 2100 cm-1 wavenumbers. Sensitivity of the measurements peak in the mid-troposphere, between 5 – 10 km.
The outlook of this work is to produce a long-term OCS satellite observational data set that provides fresh insight to the spatial distribution and trend of atmospheric OCS. Here, we present subsets of data in the form of case studies for different geographic regions and time periods.
How to cite: Cartwright, M. P., Harrison, J. J., and Moore, D. P.: Retrievals of Atmospheric Carbonyl Sulfide from IASI, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-10373, https://doi.org/10.5194/egusphere-egu21-10373, 2021.
The fire-induced carbon emission in Equatorial Asia was estimated using the inverse system named NICAM-based Inverse Simulation for Monitoring (NISMON) carbon dioxide (CO2). The analysis was performed with the four-dimensional variational method for 2015, when the big El Niño was occurred. NISMON-CO2 extensively used high-precision atmospheric mole fraction data of CO2 from the commercial aircraft observation project of Comprehensive Observation Network for TRace gases by AIrLiner (CONTRAIL). Furthermore, independent atmospheric CO2 and carbon monoxide data from National Institute for Environmental Studies (NIES) Volunteer Observing Ship (VOS) Programme were used to elucidate the validity of the estimated fire-induced carbon emission. Finally, using both CONTRAIL and NIES-VOS CO2 data, the inverse analysis indicated 273 Tg C for fire emission during September - October 2015. This two-month-long emission accounts for 75% of the annual total fire emission and 45% of the annual total net carbon flux within the region, indicating that fire emission is a dominant driving force of interannual variations of carbon fluxes in Equatorial Asia. In the future warmer climate condition, Equatorial Asia would experience more severe droughts and have risks for releasing a large amount of carbon into the atmosphere. Therefore, the continuation of these aircraft and shipboard observations is fruitful for reliable monitoring of carbon fluxes in Equatorial Asia.
How to cite: Niwa, Y., Sawa, Y., Nara, H., Machida, T., Matsueda, H., Umezawa, T., Ito, A., Nakaoka, S.-I., Tanimoto, H., and Tohjima, Y.: Inverse analysis of fire-induced carbon emission from Equatorial Asia in 2015 with CONTRAIL and NIES-VOS data, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-7005, https://doi.org/10.5194/egusphere-egu21-7005, 2021.
We present results from the sixteenth annual Greenhouse Gas Bulletin (https://library.wmo.int/doc_num.php?explnum_id=10437) of the World Meteorological Organization (WMO). The results are based on research and observations performed by laboratories contributing to the WMO Global Atmosphere Watch (GAW) Programme (https://community.wmo.int/activity-areas/gaw).
The Bulletin presents results of global analyses of observational data collected according to GAW recommended practices and submitted to the World Data Center for Greenhouse Gases (WDCGG). Bulletins are prepared by the WMO/GAW Scientific Advisory Group for Greenhouse Gases in collaboration with WDCGG.
Observations used for the global analysis are collected at more than 100 marine and terrestrial sites worldwide for CO2 and CH4 and at a smaller number of sites for other greenhouse gases. The globally averaged surface mole fractions calculated from this in situ network reached new highs in 2019, with CO2 at 410.5 ± 0.2 ppm, CH4 at 1877 ± 2 ppb, and N2O at 332.0 ± 0.1 ppb. These values constitute, respectively, 148%, 260% and 123% of pre-industrial (before 1750) levels. The increase in CO2 from 2018 to 2019 (2.6 ppm) was larger than that observed from 2017 to 2018 and larger than the average annual growth rate over the last decade. For CH4, the increase from 2018 to 2019 (8 ppb) was slightly smaller than that observed from 2017 to 2018 but still greater than the average annual growth rate over the last decade. For N2O, the increase from 2018 to 2019 (0.9 ppb) was lower than that observed from 2017 to 2018 and practically equal to the average annual growth rate over the past 10 years. The National Oceanic and Atmospheric Administration (NOAA) Annual Greenhouse Gas Index (AGGI) shows that from 1990 to 2019, radiative forcing by long-lived greenhouse gases increased by 45%, with CO2 accounting for about 80% of this increase.
The Bulletin highlights the potential impact of anthropogenic emission reductions due to COVID-19 lockdown measures on the levels of atmospheric concentrations of GHGs. These changes have been especially pronounced in urban areas and were visible in traditional pollutants as well as in greenhouse gases. However, the reduction in anthropogenic emissions due to confinement measures will not have a discernible effect on global mean atmospheric CO2 in 2020 as this reduction will be smaller than, or at most, similar in size to the natural year-to-year variability of atmospheric CO2. Direct measurements of the CO2 fluxes by ICOS directly demonstrated GHG emission reductions in a number of cities.
The Bulletin also describes the emission reduction opportunities related to methane. These opportunities are provided by emerging capabilities of methane observations from space and advances in transport modeling that allow for better source attribution and quantification. Globally averaged methane mole fraction has been increasing since 2007. Long-term observations and analysis of methane isotopic composition shed some light on this increase. The observed trend in δ13C-CH4 is explained by a combined increase in microbial and fossil emissions. This trend points to the likely scenario that the methane increase is largely driven by the growing demand for energy and food.
How to cite: Tarasova, O., Vermeulen, A., Sawa, Y., Houweling, S., and Dlugokencky, E.: The state of greenhouse gases in the atmosphere using global observations through 2019, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-4409, https://doi.org/10.5194/egusphere-egu21-4409, 2021.
Methane (CH4) is the second most important atmospheric greenhouse gas after carbon dioxide. Global concentrations of CH4 have been rising in the last decade and our understanding of what is driving the increase remains incomplete. Natural sources, such as wetlands, contribute to the uncertainty of the methane budget. However, anthropogenic sources, such as fossil fuels, present an opportunity to mitigate the human contribution to climate change on a relatively short timescale, since CH4 has a much shorter lifetime than carbon dioxide. Therefore, it is important to know the relative contributions of these sources in different regions.
We have investigated the inter-annual variation (IAV) and rising trend of CH4 concentrations using a global 3-D chemical transport model, TOMCAT. We independently tagged several regional natural and anthropogenic CH4 tracers in TOMCAT to identify their contribution to the atmospheric CH4 concentrations over the period 2009 – 2018. The tagged regions were selected based on the land surface types and the predominant flux sector within each region and include subcontinental regions, such as tropical South America, boreal regions and anthropogenic regions such as Europe. We used surface CH4 fluxes derived from a previous TOMCAT-based atmospheric inversion study (Wilson et al., 2020). These atmospheric inversions were constrained by satellite and surface flask observations of CH4, giving optimised monthly estimates for fossil fuel and non-fossil fuel emissions on a 5.6° horizontal grid. During the study period, the total optimised CH4 flux grew from 552 Tg/yr to 593 Tg/yr. This increase in emissions, particularly in the tropics, contributed to the increase in atmospheric CH4 concentrations and added to the imbalance in the CH4 budget. We will use the results of the regional tagged tracers to quantify the contribution of regional methane emissions at surface observation sites, and to quantify the contributions of the natural and anthropogenic emissions from the tagged regions to the IAV and the rising methane concentrations.
Wilson, C., Chipperfield, M. P., Gloor, M., Parker, R. J., Boesch, H., McNorton, J., Gatti, L. V., Miller, J. B., Basso, L. S., and Monks, S. A.: Large and increasing methane emissions from Eastern Amazonia derived from satellite data, 2010–2018, Atmos. Chem. Phys. Discuss., https://doi.org/10.5194/acp-2020-1136, in review, 2020.
How to cite: Dowd, E., Wilson, C., Chipperfield, M., and Gloor, M.: Quantifying the contribution of regional methane emissions to the global methane budget between 2008 and 2018 using the TOMCAT chemical transport model, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-6104, https://doi.org/10.5194/egusphere-egu21-6104, 2021.
The first Infrared Atmospheric Sounding Instrument (IASI) on the Metop satellites suite has achieved more than 13 years of continuous operation. The instrument stability and the consistency between the different instruments on the successive Metop (A, B and C) is remarkable and offer the potential to investigate trends in the concentration of various species better than with any other previous or current hyperspectral IR sounder. The low noise of IASI radiances is also such that even weakly absorbing species can be identified, on single or at least on averaged spectra. In this work we exploit the first decadal record of IASI measurements to (1) detect and monitor halogenated compounds regulated by the Montreal protocol (CFCs) or used as substitutes (HCFCs, HFCs), as well as fluorinated compounds (CF4, SF6) and potentially short lived chlorine species, for which substantial emissions are suspected (2) give a first assessment of the trend evolution of these species over the 2008-2017 period covered by IASI on Metop-A. This is done by targeting various geographical areas on the globe and examining the remote oceanic and continental source regions separately. The trend evolution in the different chemical species, either negative or positive, is validated against what is observed from ground-based measurement networks. We will conclude by assessing the usefulness of IASI and follow-on mission to contribute to global measurements of ozone depleting substances.
How to cite: De Longueville, H., Clarisse, L., Franco, B., Whitburn, S., Clerbaux, C., Camy-Peyret, C., and Coheur, P.-F.: Detecting and assessing trends of CFCs and substitutes from IASI measurements, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-10660, https://doi.org/10.5194/egusphere-egu21-10660, 2021.
Non-target screening consists in searching for all present substances in a sample, suspected or unknown, with very little prior knowledge about the sample. This approach has been introduced more than a decade ago in the field of water analysis or forensics, but is still very scarce in the field of indoor and atmospheric trace gas measurements, despite the urgent need for a better understanding of the composition of the atmosphere.
Recently, we have installed a novel analytical system at the Jungfraujoch high alpine station (3500 m.a.s.l., Switzerland), allowing us to conduct non-target screening of the atmosphere. The system is composed of a preconcentration unit followed by gas chromatography (GC), electron ionisation (EI), and time-of-flight high-resolution mass spectrometry (HRMS). This allows screening the air for all mass fragments from approx. 25 m/z up to 300 m/z, produced by compounds with boiling points from -128 °C (NF3, CF4) to +140 °C (e.g., CHBr3, chlorobenzene, parachlorobenzotrifluoride PCBTF).
Here, we present a new and innovative method to detect and identify unknown organic substances in ambient air using GC-EI-HRMS. We developed an algorithm combining the identification of atom assemblage for the detected fragments and the reconstruction of a pseudo-fragmentation tree, linking fragments belonging to the same substance. This supports in particular the identification of substances for which no mass spectrum is registered in databases. Moreover, we developed a quality control strategy to ensure that the compounds have been correctly identified and are separated from potential coelutants.
Finally, we present a selection of halogenated compounds newly detected in air, measured for the first time at the Jungfraujoch station.
How to cite: Guillevic, M., Vollmer, M. K., Hill, M., Schlauri, P., Guillevic, A., Emmenegger, L., and Reimann, S.: New halogenated trace gases discovered by non-target screening of the atmosphere at the Jungfraujoch high alpine station (Switzerland), EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-14313, https://doi.org/10.5194/egusphere-egu21-14313, 2021.
Accurate measurements of ozone in the upper tropical troposphere and lower stratosphere (UTLS) are challenging for most measuring systems, yet of great importance for the understanding of the chemical and dynamical processes in this region.
Balloon-borne observations using Electrochemical Concentration Cell (ECC) ozone sondes are the most widely used in situ technology to measure vertical profiles of ozone in networks such as the Southern Hemisphere ADditional Ozonesondes (SHADOZ) network of tropical and subtropical ozone sonde stations.
The tropical upper troposphere and the layers of near-zero ozone within the ozone hole are most sensitive to processing and preparation variations that may affect the accuracy and possibly trend estimates of ozone in low ozone regions. It is now appreciated that the complex chemistry within the ECC used to detect ozone exhibits two different time constants (τfast≈20 s, τslow≈25 min), which modify the response of the ECC during a profile. Although not well understood, the chemistry of the slow reaction is likely to represent what has conventionally been assumed a constant “background current”. The fast reaction causes some delay in the response of the ECC to changes in the vertical profile of ozone. Here we show how correcting for both improves the estimate of the lowest ozone concentration in the upper troposphere as well as the steepness of the gradient in the transition into the stratosphere. The steady state bias, which describes the contribution of the slow reaction, is the largest source of uncertainty overall; the response time of the fast reaction dominates the uncertainty in the region of the sharp gradient of ozone above the tropopause.
How to cite: Vömel, H., Stauffer, R., Selkirk, H., Thompson, A., Diaz, J. A., Kollonige, D., Corrales, E., and Alan, A.: The importance of the time response of Electrochemical Concentration Cell (ECC) ozone sondes for measurements of tropical upper tropospheric and lower stratospheric ozone, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-13634, https://doi.org/10.5194/egusphere-egu21-13634, 2021.
The distribution of ozone in the atmosphere is relevant for air pollution and radiative forcing. This distribution features complex spatial and temporal variability, set by balances between chemical production, loss processes, and advection. At present, the way in which ozone comparison regions are defined relies on somewhat arbitrarily drawn boundaries. In an effort to develop a more general, data-derived method for defining coherent regimes of ozone structure, we apply an unsupervised classification technique called Gaussian Mixture Modelling (GMM). We apply GMM to the output from the UKESM1 coupled climate model, including the historical run and two of the future climate projections. GMM identifies different ozone profile classes without using any latitude or longitude information, thereby highlighting coherent ozone structure regimes. We determine each of the model data set contains 9 groups of unique vertical classes. The classes depend on latitude, even though GMM was not given any latitude information. Polar and subpolar classes show low tropopause and low tropospheric ozone, and the tropical classes have high tropopause. Northern hemisphere high latitude classes have higher stratospheric ozone than southern hemisphere high latitude classes. We analyze how the spatial extent of the classes changes under different scenarios by comparing classes in SSP126 and SSP585 with a historical simulation. This work suggests that GMM may be a useful method for identifying coherent ozone regimes for comparing different model results and observational data.
How to cite: Fahrin, F., Jones, D., Wu, Y., and Archibald, A.: Unsupervised classification of ozone profiles from UKESM1, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-3752, https://doi.org/10.5194/egusphere-egu21-3752, 2021.
Solar flux variations associated with the 11-year solar cycle are believed to exert an important climate forcing via changes in stratospheric ozone. However, our understanding of the ozone solar cycle signal (SCS) was significantly revised with the availability of updated SAGE II v7 data. For example, Dhomse et al. (Geophys. Res. Lett., 2016) analysed SAGE II v7 data to show a much smaller upper stratosphere ozone SCS, as well as a more realistic ozone-temperature anti-correlation, that agreed with the relatively short HALOE and AURA-MLS data records. Here, we analyse AURA-MLS satellite data and output from the TOMCAT 3D chemical transport model (CTM) to estimate the ozone SCS for the 2005-2020 period, which covers one of smallest solar cycles (number 24) of the last 100 years. Along with a control simulation, various model simulations with combinations of different dynamical (e.g. ERA5, ERA-Interim, fixed), chemical (e.g. constant ozone depleting substances) and solar flux (NRL, SATIRE, SORCE solar irradiances) forcings are analysed.
Our earlier studies use an Ordinary Least Square (OLS) multivariate regression model to estimate the SCS. However, most of the relevant atmospheric variables are correlated. Hence, to avoid this collinearity problem, we use an ensemble of Lasso and Ridge multivariate regression models and their variants to quantify the SCS in stratospheric ozone. Overall, both MLS and the CTM simulations show a vertical “double-peak”-structured ozone SCS in the tropical stratosphere. However, compared to previous studies, the regression ensemble mean shows a somewhat larger signal in the middle stratosphere and does not show a negative SCS in the lower and upper stratosphere. Our analysis also shows significant inter-hemispheric and seasonal differences in lower stratospheric ozone trends over the 2005-2020 time period (i.e. recent ozone recovery phase). Our CTM simulations also confirm that recent negative ozone trends in the northern hemispheric mid-latitude lower stratosphere (Chipperfield et al., Geophys. Res. Lett., 2018), are primarily caused by changes in the stratospheric circulation.
How to cite: Chipperfield, M., Dhomse, S., Feng, W., and Hossaini, R.: Revising the 11-year Solar Cycle Response in Stratospheric Ozone Using an Ensemble of Lasso and Ridge Regression Models, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-11070, https://doi.org/10.5194/egusphere-egu21-11070, 2021.
Brewer spectrophotometers are one of the most widely used instruments for measuring the Total Ozone Column (TOC) in the world, which is obtained by measuring solar radiance at a set of UV sensible wavelengths. To date, the value of the uncertainty in these measures has not been obtained quantitatively. With this work, we have carried out an exhaustive study of the uncertainties that have affected the measure of TOC with data obtained during the first ATMOZ field campaign carried out between 12-25 September 2016 at the Izaña Atmospheric Observatory, Canary Islands, Spain at 2373 m.a.s.l., organized by the Spanish Meteorological Agency (AEMET) and the World Radiation Center (PMOD/WRC). For this, we have differentiated between three uncertainty components: related to the measure (dead time, filters, etc), model components (cross sections, etc) and atmospheric components (effective temperatures and heights, etc). The total uncertainty has been obtained through the propagation of errors of the different parameters, and the cross-correlations between the model and atmospheric components, using two different data sets. With the standard algorithm we have obtained the expected 2σ-uncertainty, around 2.4% for the three RBCC-E Triad Brewer double-monochromator spectrophotometers studied (Br157, Br183 and Br185) at noon and using the Extra-Terrestrial Constant (ETC) Langley calibration. On the other hand, for these same spectrophotometers, and using an updated algorithm the 2σ-uncertainty are reduced to values around 1.3 % in the TOC measurement. In first approximation, ignoring the cross-correlations the ozone absorption coefficient covers the most of total ozone uncertainty in both algorithms, followed by the ozone optical mass, the ETC and the measurement uncertainties.
How to cite: Parra-Rojas, F. C., Redondas, A., Berjón, A., and López-Solano, J.: A new data set for the Brewer spectrophotometer uncertainty budget in the total ozone column measurements, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-15316, https://doi.org/10.5194/egusphere-egu21-15316, 2021.
Stratospheric Ozone (O3) absorbs biologically harmful solar ultraviolet radiation (most of the UV‑B radiation) and keeps it from reaching the surface. Such UV radiation is destructive of genetic cellular material in plants and animals, as well as human beings. Without the ozone layer, life on the surface of the Earth would not be possible as we know it.
As part of its work the German Weather Service (DWD) provides UV index maps to warn the population in Germany of excessive UV exposure []. For this purpose, global ICON data, external ozone data and an external UV model is used.
This study aims to create a self-consistent framework to generate UV index maps entirely from the non-hydrostatic global modelling system ICON []. For this purpose, a linearized ozone scheme (LINOZ) [] will be optimized and the forecast functionality of ICON-ART [][] (ICOsahedral Non-hydrostatic – Aerosols and Reactive Trace gases) will be extended. For the derivation of UV radiation fluxes and indices a radiative transfer model for solar radiation (Cloud-J) [] shall be implemented and extended. Since the entire framework is to be used at the DWD during ongoing operations, a functionality with very low computational effort is required.
Here we present the first results of the UV radiation flux through the atmosphere and its diurnal variation. Furthermore, the influence of clouds on the UV radiation flux is considered.
[] Zängl, G., et al. (2014), The ICON (ICOsahedral Non-hydrostatic) modelling framework of DWD MPI-M: Description of the non-hydrostatic dynamical core. Q.J.R. Meteorol. Soc., doi:10.1002/qj.2378
[] McLinden, C. A., et al. (2000), Stratospheric ozone in 3-D models: A simple chemistry and the cross-tropopause flux, Journal of Geophysical Research: Atmospheres, doi:10.1029/2000JD900124
[] Rieger, D., et al. (2015), ICON-ART - A new online-coupled model system from the global to regional scale, Geosci. Model Dev., doi:10.5194/gmd-8-1659-2015
[] Schröter, et al. (2018), ICON-ART 2.1: a flexible tracer framework and its application for composition studies in numerical weather forecasting and climate simulations. Geosci. Model Dev., doi:10.5194/gmd-11-4043-2018
[] Prather, M.J. (2015), Photolysis rates in correlated overlapping cloud fields: Cloud-J 7.3c. Geosci. Model Dev., doi:10.5194/gmd-8-2587-2015
How to cite: Weber, S., Ruhnke, R., Braesicke, P., and Scharun, C.: Prognostic Ozone for ICON: Enabling UV Forecasts, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-8783, https://doi.org/10.5194/egusphere-egu21-8783, 2021.
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