The divergence, i.e. the spatial derivative of the horizontal flux, yields the local balance of sources of sinks. Strong positive divergence is observed for (and allows to quantify) NO_x emissions from point sources like power plants. Within the downwind plume, NO₂ changes due to (a) further NO to NO₂ conversion (NO₂ source, positive divergence) and (b) NO₂ reaction with OH (NO₂ sink, negative divergence).

In this study we aim to disentangle and quantify these competing effects based on the divergence of the observed NO₂ flux. We focus on large and isolated power plants where additional sources are negligible. Goal is to determine the time scales for the NO to NO₂ conversion and the NO₂ lifetime for power plant plumes.

How to cite: Beirle, S. and Wagner, T.: Investigating NO2 processing in power plant plumes from TROPOMI, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-2121, https://doi.org/10.5194/egusphere-egu24-2121, 2024.

High-resolution spaceborne emission inversions play a crucial role in independent emission monitoring, small-scale pollution modelling, and exposure estimation. However, spaceborne emission inversion at 1-km resolution is still a challenge due to the insufficiency of satellite observations, along with limitations such as computational costs and meteorological data. The spatial resolutions of existing satellite-based NO₂ observations (e.g. TROPOMI: nadir pixel of ~3.5×5.5 km²) fall short in capturing spatial features at 1-km resolution. Here we develop an innovative technique to integrate high-resolution geodata in emission inversions. This technique introduces constraints based on geodata associated with emissions to inversions independent of predefined downscaling schemes. Our inversions show advanced results of NOx emissions with detailed spatial patterns at small scale, especially for sources relevant to traffic and marine shipping which are of large uncertainties in current inventories.

How to cite: Kong, H., Lin, J., Zhang, Y., Wang, S., and Xu, C.: 1-km resolution inversion of NOx emissions based on satellite constrained by geodata, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-2865, https://doi.org/10.5194/egusphere-egu24-2865, 2024.

Questions about how regulations have shaped ozone pollution regionally cannot be answered by studying observed surface ozone concentrations alone, as we must precisely determine ozone production rates, which refer to the amount of ozone molecules photochemically produced in the atmosphere. Through an extensive suite of NASA's airborne campaigns such as DISCOVER-AQs, KORUS-AQ, INTEX-B, SENEX, and ATOMs, constraining a well-characterized chemical box model, we establish a simple but robust relationship between ozone production rates and various observable parameters; some of these factors, fortunately, are being measured or constrained by satellite observations, which has allowed us to create the first-ever maps of ozone production rates across the globe. We quantitatively and qualitatively assess this product's efficacy through independent airborne campaigns and by contrasting extreme events to a norm. We have a clear path forward to enhance this innovative product using agile machine learning algorithms for the years from 2005 to 2024, along with its well-characterized error budget.

How to cite: Souri, A., González Abad, G., Wolfe, G., Johnson, M., Duncan, B., and Verhoelst, T.: Early Results of Ozone Production Rate Estimates Using Satellite Observations: Insights From Numerous NASA Atmospheric Composition Campaigns, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-3562, https://doi.org/10.5194/egusphere-egu24-3562, 2024.

Nitrogen dioxide (NO₂) in the lower marine atmosphere, mainly emitted by maritime shipping, plays a crucial role in air pollution formation and global human health. However, few measurements of marine atmospheric NO₂ hinder knowledge of trace gas trends and atmospheric chemistry evolution due to shipping emissions. In this study, we use long-term satellite observations of tropospheric NO₂ column from the European TROPOspheric Monitoring Instrument (TROPOMI) and the Chinese Environmental trace gases Monitoring Instrument (EMI) to analyze marine atmospheric NO₂ variations, especially during the global COVID-19 pandemic and escalating geopolitical crises. First, we demonstrate the detection of NO₂ enhancements along shipping routes, including the North Atlantic route, the North Pacific route, and the Cape route, indicating significant emissions of atmospheric NO₂ from on-ocean shipping. Second, we observe and quantify the response of marine atmospheric NO₂ concentrations to major shipping events, such as the Suez Canal blockage, the Los Angeles-Long Beach port congestion, and the Russia-Ukraine war, resulting in local NO₂ concentration variations of approximately 40% decrease to 70% increase. Long-term analysis reveals reduced NO₂ concentrations in most coastal ports and maritime shipping routes during the COVID-19 lockdown, with reductions exceeding 50% or durations lasting up to 200 days. However, some rapidly developing ports, such as Beibu Gulf (China) and Dakar (Senegal), did not experience a decrease in NO₂ concentrations, suggesting that local authorities need to pay more attention to these fast-growing yet underestimated emission sources. In addition, by excluding the impact of meteorology using statistical models, we find that the current Emission Control Area (ECA) policies have effectively reduced NO₂ concentrations in Chinese coastal ports. These results contribute to understanding spatiotemporal characteristics of marine atmospheric NO₂, including ports and open-sea shipping routes, and guide further ECA policies to control marine NO₂ pollution.

How to cite: Wang, X., Zhang, C., and Liu, C.: Satellite unravels recent changes in atmospheric nitrogen oxides emissions from global ocean shipping, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-4517, https://doi.org/10.5194/egusphere-egu24-4517, 2024.

Formaldehyde (HCHO) is a toxic and harmful air pollutant to humans, animals, and plants and is an essential precursor of PM_2.5 and ozone compound pollution. Few studies have focused on HCHO in Tibet, the third pole with a unique ecosystem that requires protection. Here, we investigate the spatial-temporal distribution of HCHO from 2013 to 2021 and its influencing factors from satellite observations in Tibet. We found that the average HCHO VCD in Tibet presents a significant annual growth rate of 2.25%/yr, which is similar to that in India and even higher than that in most of the world, including eastern China. Moreover, HCHO VCD in the eastern region of Tibet shows no seasonal pattern, unlike other areas. The anomalous variation in HCHO concentrations in Tibet is primarily attributed to long-distance transnational transport from incomplete combustion in India Assam. Our results help strengthen concerns about atmospheric environmental management in Tibet.

How to cite: Xu, Y., Su, W., and Liu, C.: Unexpected HCHO transnational transport: Influence on the temporal and spatial distribution of HCHO in Tibet from 2013 to 2021 based on satellite, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-4826, https://doi.org/10.5194/egusphere-egu24-4826, 2024.

In this study, TROPOspheric Monitoring Instrument (TROPOMI) observations were resampled to obtain 0.01° × 0.01° NO₂ VCD (vertical column density) of Yangtze River Delta (YRD), China. The adjusted Exponentially-Modified Gaussian (EMG) model was improved to estimate the quantified nitrogen oxides (NO_X) emission. The estimation in typical cities under regionally polluted YRD area has a good correlation with Multi-resolution Emission Inventory for China (MEIC) emission with R more than 0.9 but lower results mainly due to the underestimation of NO₂ VCD by TROPOMI in polluted areas. On this basis, using the adjusted EMG method, this study quantified NO_X emission in Shanghai during 2022 lockdown period as 32.60 mol/s with a decrease of 50–80%, which was mainly contributed by the transportation and industrial sectors. The significant reduction of NO_X emission in Shanghai is much higher than that of volatile organic compounds (VOCs), which led to dramatic changes in formaldehyde-to-nitrogen dioxide ratio (HCHO/NO₂, FNR). Thus, when enforcing regulation on NO_X emission control in the future, coordinately reducing VOCs emission should be implemented to mitigate urban O₃ pollution.

This work was supported by Sino-German Mobility Program (M-0509) and National Natural Science Foundation of China (grant number 42075097, 22176037, 42375089, 22376030).

How to cite: Xue, R., Wang, S., and Zhou, B.: Assessing NOX emission reduction of Shanghai during city-wide lockdown from TROPOMI high spatial resolution observations, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-5854, https://doi.org/10.5194/egusphere-egu24-5854, 2024.

Apart from the loss of life and property, the hostilities, which started on February 24, 2022, with the invasion by Russian armed forces into Ukraine, are altering Ukraine’s environment. In this study, we will present the major findings of Malytska et al., 2024, discussing the changes in tropospheric pollution, specifically nitrogen dioxide (NO₂), as a consequence of military activities. This study uses the TROPOspheric Monitoring Instrument (TROPOMI) and Visible Infrared Imaging Radiometer Suite (VIIRS) satellite observations, Global Fire Assimilation System (GFAS) wildfire emission inventory, European Centre for Medium-Range Weather Forecasts (ECMWF) daily ERA5 reanalysis data, and the Hybrid Single-Particle Lagrangeian Integrated Trajectory analysis model (HYSPLIT) 5.2 to quantify the spatiotemporal distribution of tropospheric NO₂, its changes and transport during the first three months of the armed conflict in Ukraine. This provides insights into the impact of hostilities on local air quality, as well as regional and transborder pollution.

We discuss NO₂ variability with a particular emphasis on comparing periods before and during hostilities to differentiate the effects of COVID-19 restrictions and the hostilities on NO₂ emissions over Ukraine. The retrieved emissions show a temporal reduction in NO₂ emission in industrial areas, comparable to the COVID-19 pandemic lockdown, whereas the NO₂ tropospheric vertical column locally increased in the areas of conflict. Based on the TROPOMI and VIIRS data, we linked the major fires caused by the conflict to air pollution and found that hostilities led to more frequent and intense fires in conflict zones deteriorating air quality in the region. To investigate the impact of the hostilities on atmospheric pollution, we analysed nitrogen oxide (NO_x) emission and injection altitude of fire, using the GFAS data. It was found that fires in conflict-affected areas exhibit greater intensity, characterized by larger plume top heights and higher rates of emission, in comparison to fires located far from the front line or resulting from isolated strikes. To demonstrate that increased fire activities contribute to pollution at both local and regional levels, we provide a case study of the fire episode of March 19-23, 2022, in the Kyiv region, coinciding with the active stage of the conflict and the defense of the capital, Kyiv. The simulations of HYSPLIT version 5.2 forward trajectories model showed that a smoke-particle-included air mass, related to the fires in the Chornobyl Exclusion Zone, was transported to Poland and countries of the Baltic region at the height of 1.5-3 km within 72 hours. A plume of NO₂, which originated from fires in the Chornobyl Exclusion Zone on March 20, 2022, was observed in Poland the following day.

References:

Malytska L., Ladstätter-Weißenmayer A., Galytska E, and. Burrows J.P. Assessment of environmental consequences of hostilities: Tropospheric NO₂ vertical column amounts in the atmosphere over Ukraine in 2019–2022. Atmospheric Environment 318 (2024) 120281, DOI: https://doi.org/10.1016/j.atmosenv.2023.120281

How to cite: Malytska, L., Galytska, E., Ladstätter-Weißenmayer, A., Burrows, J. P., and Moskalenko, S.: Tropospheric NO2 changes in Ukraine (2019–2022) amidst the Russian-Ukrainian conflict and consequent transboundary effects, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-7964, https://doi.org/10.5194/egusphere-egu24-7964, 2024.

Ammonia (NH₃) is an important air pollutant which, as precursor of fine particulate matter, raises public health issues. This study analyzes 2.5-years of NH₃ observations derived from ground-based (miniDOAS) and satellite (IASI) remote sensing instruments to quantify, for the first time, temporal variabilities (from interannual to diurnal) of NH₃ concentrations in Paris.

The IASI and miniDOAS datasets are found to be in relatively good agreement (R>0.70) when atmospheric NH₃ concentrations are high and driven by regional agricultural activities. Over the investigated period (January 2020 – June 2022), NH₃ average concentrations in Paris measured by the miniDOAS and IASI are 2.23 μg.m^-3 and 7.10x10¹⁵ molecules.cm^-2, respectively, which are lower or equivalent to those documented in other urban areas. The seasonal and monthly variabilities of NH₃ concentrations in Paris are driven by sporadic agricultural emissions influenced by meteorological conditions, with NH₃ concentrations in spring up to 2 times higher than in other seasons.

The potential source contribution function (PSCF) reveals that the close (100-200km) east and northeast regions of Paris constitute the most important potential emission source areas of NH₃ in the megacity.

Weekly cycles of NH₃ derived from satellite and ground-based observations show different ammonia sources in Paris. In spring, agriculture has a major influence on ammonia concentrations and, in the other seasons, multi-platform observations suggest that ammonia is also controlled by traffic-related emissions.

In Paris, the diurnal cycle of NH₃ concentrations is very similar to the one of NO₂, with morning enhancements coincident with intensified road traffic. NH₃ evening enhancements synchronous with rush hours are also monitored in winter and fall. NH₃ concentrations measured during the weekends are consistently lower than NH₃ concentrations measured during weekdays in summer and fall. This is a further evidence of a significant traffic source of NH₃ in Paris.

How to cite: Viatte, C., Guendouz, N., Dufaux, C., Hensen, A., Swart, D., Van Damme, M., Clarisse, L., Coheur, P., and Clerbaux, C.: Ammonia in Paris derived from ground-based open-path and satellite observations, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-8072, https://doi.org/10.5194/egusphere-egu24-8072, 2024.

Sulfur dioxide (SO₂), emitted from volcanic eruptions, can have a major impact on the environment and society. While nadir-viewing satellites have been providing precise information on its Vertical Column Density (VCD) for several decades, the retrieval of its Layer Height (LH) is a more recent development, although it is important for the aviation safety, estimation of SO₂ emissions, understanding of volcanic processes and climate research. In the Ultraviolet (UV), the current algorithms are often time-consuming and still lack sensitivity, especially in the presence of aerosols. 

Our research aims at developing an improved SO₂ LH (and VCD) retrieval algorithm for the TROPOspheric Monitoring Instrument (TROPOMI). While the third spectral band of TROPOMI is traditionally used for sulfur dioxide, a shorter UV region has been exploited here to take advantage of the strong absorption of SO₂ in the second band. As a demonstration case, Slant Column Density (SCD) retrievals in band 2 were carried out using the Covariance-Based Retrieval Algorithm (COBRA) [1]. We show that SO₂ SCDs from both spectral bands are generally in excellent agreement. However, the results in band 2 reveal a greater sensitivity to SO₂ than in band 3.

Motivated by this result, we performed SO₂ plume height retrievals on an extensive set of synthetic spectra representative of TROPOMI observation conditions, using the Look-Up Tables Covariance-Based Retrieval Algorithm (LUT-COBRA) [2]. The SO₂ LHs and VCDs we find from the second band are more accurate, and the associated retrieval errors appear to be considerably reduced in comparison to those of the band 3.

In addition, sensitivity analyses were conducted to further characterise the wavelength dependence and effect of some observation conditions on the quality of these retrievals. More specifically, we assess the impact of the temperature, air density, ozone profile and VCD, SO₂ absorption cross sections, surface albedo and height as well as the SO₂ profile shape. 

Finally, we present the next steps to further develop the LUT-COBRA approach and application to TROPOMI band 2 measurements. 

[1] N. Theys et al. Atmospheric Chemistry and Physics, 21(22):16727–16744, 2021.
[2] N. Theys et al. Atmospheric Measurement Techniques, 15(16):4801–4817, 2022.

How to cite: Fabris, L., Theys, N., Clarisse, L., Brenot, H., Yu, H., van Gent, J., Vlietinck, J., and Van Roozendael, M.: Sensitivity tests for improved retrievals of SO2 plume height from TROPOMI observations, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-8314, https://doi.org/10.5194/egusphere-egu24-8314, 2024.

The development of MUSICA IASI processing was initiated as part of the MUSICA (Multi-platform remote Sensing of Isotopologues for investigating the Cycle of Atmospheric water) project funded by the European Research Council. This processor works with IASI (Infrared Atmospheric Sounding Interferometer) radiances measured under cloud-free conditions, and, using optimal estimation, derives vertical distributions of water vapor, ratios between water vapor isotopologues, and several trace gases including greenhouse gases, methane and nitrous oxide. In accordance with the FAIR (findable, accessible, interoperable, reusable) principles, all MUSICA IASI products are freely available together with their observation specific averaging kernels and uncertainty covariances. Recently, retrievals of sulfur dioxide (SO₂), peroxyacetyl nitrate (PAN), acetic acid and acetone have been included, in order to account for their important spectroscopic signals in case of volcanic eruptions and biomass burning events, respectively. 

Here, we present the MUSICA IASI SO₂ retrieval setup. A particularity is the use of a logarithmic SO₂ concentration scale, which facilitates a reliable detection of the altitude where the SO₂ plume is situated (retrieved from the spectral signal, no a priori assumptions of an SO₂ plume height required). We document the superiority of this retrieval setup compared to a retrieval on a linear SO₂ concentration scale. In addition, we empirically demonstrate the quality of the SO₂ profile data in the preliminary results of three different volcano eruption events at three different latitude regions: 2019 Raikoke (48°N), 2021 La Palma (Cumbre Vieja, 29°N), and 2022 Hunga Tonga-Hunga Ha’apai (20°S). The amount of SO₂ and the SO₂ plume height are different for the three events. We show that the MUSICA IASI product is able to correctly capture these differences.

The availability of individual averaging kernels allows a quantitative inter-comparison to other SO₂ data products. For SO₂ plumes in the low and middle troposphere, we will explore respective comparison possibilities to data obtained from Ticosonde in-situ measurements. For SO₂ plumes in the upper troposphere or stratosphere, we plan to use data provided by MLS (Microwave Limb Sounder instrument aboard the NASA/Aura satellite). IASI SO₂ products generated by other processors and TROPOMI/S5P SO₂ products will also be potential candidates for inter-comparison studies.

How to cite: Lo, N. Y., Schneider, M., Shahzadi, K., Hase, F., Braesicke, P., Caspart, R., and Streit, A.: Retrieval of vertical concentration profiles of SO2 using the IASI satellite instrument, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-9075, https://doi.org/10.5194/egusphere-egu24-9075, 2024.

Ammonia (NH₃) is an atmospheric pollutant mainly emitted by the agricultural sector, which has an effect on public health since it is a precursor of fine particles (PM_2.5). The diurnal variability of NH₃ in the atmosphere and its transformation into particles are poorly constrained and strongly depend on meteorological parameters, in particular temperature. This strongly influences our ability to correctly simulate NH₃ emissions and associated particulate pollution events in atmospheric models

The IRS (InfraRed Sounder) instrument which will be launched on the MTG (Meteosat Third Generation) satellite into geostationary orbit in late 2024, will offer the ability to evaluate NH₃ diurnal variabilities and its dependence on atmospheric temperature with frequent measurements (every 30-45 minutes over Europe and Africa) and fine spatial resolution (4 km x 4 km at the Equator and Greenwich meridian).

This work shows the potential of the European geostationary IRS-MTG mission to capture the spatio-temporal variability of ammonia and temperature focusing on a case study over the Brittany region in France. Synthetic spectra are simulated from the 4A/OP radiative transfer model using atmospheric states derived from the CHIMERE chemistry-transport model. The IRS NH₃ observations are compared to the current IASI observations in terms of vertical sensitivity and error budget. The uncertainty analysis over the Brittany region is calculated using NH₃ Jacobians computed from the 4A/OP radiative code and the noise covariance matrix provided by each satellite.

How to cite: Guendouz, N., Viatte, C., Boynard, A., Safieddine, S., Standfuss, C., Turquety, S., Van Damme, M., Clarisse, L., Coheur, P., Armante, R., Prunet, P., and Clerbaux, C.: Assessing the future IRS-MTG NH3 and temperature observations, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-10410, https://doi.org/10.5194/egusphere-egu24-10410, 2024.

Methane (CH₄) is an important greenhouse gas (GHG), contributing about ~23% (0.62 W m^-2) of the additional radiative forcing on the troposphere due to its increased concentrations compared to pre-industrial levels. Mainly, anthropogenic sources of CH₄ are agriculture, livestock farming, fossil fuels and biomass burning. Further, natural sources are primarily wetlands, while minor ones are oceans, termites, wild animals and permafrost. There are persistent uncertainties regarding the sources of CH₄ due to limited knowledge of the processes underlying them, leading to inconsistencies between top-down and bottom-up estimates. It is relevant to reduce these uncertainties and accurately assess CH₄ emissions as it is meaningful for atmospheric modelling, climate change estimations, and policy making. Higher resolution and lower uncertainty data can benefit assimilation systems, thus increasing confidence in estimates of emission sources.

This work aims to assimilate high-resolution data from satellite observations and measurements obtained from surface stations to optimize global methane emission fields. We evaluate differences resulting from the assimilation of satellite observations at varying resolutions. Additionally, we compare different setups of the assimilation framework, using varied combinations of satellite and surface measurements, to assess potential discrepancies in the resulting emissions. The modelling framework is based on the TM5-MP (massive parallel) atmospheric chemistry-transport model, utilizing its adjoint in a four-dimensional (4DVAR) data assimilation system. Our study aims to constrain global CH₄ emissions first at a spatial resolution of 3° × 2° (longitude × latitude) for 2018 and then increase the resolution to 1° × 1°. The tropospheric CH₄ mixing ratio product slated for assimilation is acquired by the TROPOMI instrument onboard the satellite Sentinel 5-P, and retrieved using the weighting function modified differential optical absorption spectroscopy (WFMD-IUP) algorithm. This product offers enhanced coverage, especially over higher latitudes, and reduced uncertainty compared to the operational product. Conversely, near-surface CH₄ measurements are obtained from stations within the global NOAA network. Preliminary results suggest a relevant role of both the resolution of the satellite instrument and the type of data assimilated regarding convergence and final results.

How to cite: Parraguez Cerda, S., Nüß, J. R., Daskalakis, N., Schneising, O., Buchwitz, M., Vrekoussis, M., and Kanakidou, M.: Comparison of inversions of global methane emissions using TM5-MP/4DVAR with TROPOMI measurements, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-10777, https://doi.org/10.5194/egusphere-egu24-10777, 2024.

Tropospheric ozone, a critical pollutant and greenhouse gas, exhibits spatio-temporal variability, challenging satellite observations. Existing methods like the Convective Cloud Differential (CCD) and Cloud Slicing Algorithms (CSA) are standard for Tropospheric Column Ozone (TCO) retrieval but are limited to the tropics (20°S-20°N). Notably, the CCD approach has proven successful with satellite sensors like Aura OMI, MetOp GOME-2, and Sentinel-5 Precursor TROPOMI.

In this study, we present the first successful application of CCD retrieval outside the tropical region. We introduce CHORA-CCD (Cloud Height Ozone Reference Algorithm-CCD) for retrieving TCO from TROPOMI in middle latitudes. It utilises a local cloud reference sector (CLCD, CHORA-CCD Local Cloud Decision) to determine the stratospheric (above cloud) column (ACCO) ozone.  This ACCO is later subtracted from the total column in clear-sky scenes to determine the TCO. The new approach minimises the impact of variances in stratospheric ozone.

An iterative approach is used to automatically select an optimal local cloud reference sector around each retrieval grid point, varying the radius from 60 to a maximum of 600 km around the grid box, for which a mean TCO is determined until a sufficient number of ground pixels with nearly fill cloud cover are found. Due to the prevalence of low-level clouds in middle latitudes, the estimation of TCO is constrained to the column up to a  reference altitude of 450 hPa.  An alternative method is introduced to directly estimate the ACCO down to 450 hPa by Theil-Sen regression in cases where the cloud-top heights in the local cloud sector are variable. The algorithm dynamically decides between CCD and Theil-Sen method for ACCO estimation by analysing the cloud characteristics. The CLCD algorithm is further refined by introducing a homogeneity criterion for total ozone to overcome inhomogeneities in stratospheric ozone.

Monthly averaged CLCD-TCOs have been determined over the middle latitudes (60◦S-60◦N) from TROPOMI for the time period from 2018 to 2022. The accuracy of the method was investigated by comparisons with spatially collocated SHADOZ/WOUDC/NDACC ozonesondes from thirty-one stations. The validation results reveal that TCO retrievals at 450 hPa using the CLCD algorithm exhibit good agreement with ozonesondes at most stations. At the tropical station Natal (5.4°S, 35.4°W), there is an outstanding agreement between CLCD and ozonesondes, showcasing minimal bias and scatter (0.3 ± 1.0 DU). Similarly, in the subtropics over Irene (25.9°S, 28.2°E), CLCD exhibits a significantly lower bias and scatter (0.0 ± 1.4 DU). Specifically, at one of the northernmost stations, Legionowo (52.4°N, 21°E), bias and dispersion are minimal (0.4 ± 2.2 DU). Across all stations, the maximum observed bias and dispersion are below around 5 DU and 4 DU, respectively. 

In this presentation, a detailed validation of the new local CCD retrievals will be given, underlining the advantage of using the local cloud reference sector in the middle latitudes, providing an important basis for subsequent systematic applications in current and future missions of geostationary satellites.

How to cite: Maratt Satheesan, S., Eichmann, K.-U., and Weber, M.: Extension of the S5P/TROPOMI CCD tropospheric ozone retrieval to middle latitudes, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-11316, https://doi.org/10.5194/egusphere-egu24-11316, 2024.

ALTIUS (Atmospheric Limb Tracker for the Investigation of the Upcoming Stratosphere) is an atmospheric limb mission being implemented in ESA's Earth Watch programme and planned for launch in 2026.

The instrument consists of three imagers: UV (250-355 nm), VIS (440-675 nm) and NIR (600-1040 nm) channels. Each channel is able to take a snapshot of the scene independently of the other two channels, at a desired wavelength and with the requested acquisition time. The agility of ALTIUS allows for series of high vertical resolution observations at wavelengths carefully chosen to retrieve the vertical profiles of species of interest.

ALTIUS will perform measurements in different geometries to maximize global coverage: observing limb-scattered solar light in the dayside, solar occultations at the terminator, and stellar, lunar, and planetary occultations in the nightside. The primary objective of the mission is to measure high-resolution stratospheric ozone concentration profiles. Secondary objectives are the retrieval of mesospheric ozone, stratospheric aerosols particle density and extinction coefficient, NO₂, NO₃, BrO, OClO, water vapor and temperature profiles.

The Level-2 retrievals use a Levenberg-Marquardt algorithm coupled to a Tikhonov regularization scheme to limit noise amplification during the inversion process. The type and strength of regularization has a direct effect on the retrieved profile vertical resolution. Therefore, a trade-off has to be found between noise removal amplitude and vertical resolution. A study on the different regularization constraint types is performed and the regularization strength is determined using the retrieval noise error in stellar occultation mode for O₃ and NO₂ density and aerosol extinction retrievals. The ability of Tikhonov regularization to remove the effects of scintillation on the retrieved profiles is discussed. Moreover, a re-processing of GOMOS data is performed to test the validity of our approach.

How to cite: Berthelot, A., Baker, N., Demoulin, P., Franssens, G., Fussen, D., Gramme, P., Mateshvili, N., Pieroux, D., Sotiriadis, S., and Dekemper, E.: Regularization scheme in ALTIUS retrieval algorithms, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-11354, https://doi.org/10.5194/egusphere-egu24-11354, 2024.

BIOMASP+: Biogenic Volatile Organic Compounds in the Metropolitan Area of São Paulo (MASP) is a collaboration project among different French and Brazilian institutions to investigate the critical role of the biosphere-atmosphere interactions on urban pollution conditions and to evaluate how the biogenic volatile organic compounds (BVOC) affect the secondary pollutant formation.

Formaldehyde (HCHO) is the most abundant atmospheric carbonyl compound and a photochemical oxidation product of VOCs from several anthropogenic and natural sources [1]. Over São Paulo state (SP), HCHO arises from complex atmospheric interactions between a large urban area with 15 million of vehicles using four different fuel types, several industries, an extensive Atlantic Rainforest (3.9 10⁴ km²), biomass burning and thousands of farms that cover 40% (2.5 10⁵ km²) of the SP area [2]. The Metropolitan Area of São Paulo (MASP) is a highly polluted megacity [3], with concentrations that often exceed the World Health Organization guidelines, particularly for ozone and PM_2.5, which are produced by photochemical reactions, such as the formaldehyde.

Vertical formaldehyde columns data (mol/m²) were obtained from the TROPOspheric Monitoring Instrument (TROPOMI) spectrometer onboard the Sentinel-5P satellite [2], and used in the WRF-CHEM model performance evaluation. Both, the long-term simulation and the Sentinel-5P data, covered the full 2022-year.

Satellite data confirmed the spatial distribution of HCHO simulated by WRF-CHEM, indicating MASP as the main formaldehyde hotspot in the state of São Paulo [2]. For the HCHO monthly averages, the normalized cross-correlation (i.e., spatial distribution) between model and satellite remains inside the range of: 0.3 < r < 0.6.

Using the satellite time series, it was possible to identify a bias in the HCHO simulated concentrations, that reached up to 80% in 1-year of simulation. This reduced the model's ozone production by up to 60% in the end of simulation. Comparing the simulation results with ozone data from air quality monitoring stations of the state of São Paulo [4], the linear correlation was within the range of 0.4 < r² < 0.7, while the error was high (RMSE < 46.5).

A long-term (1-year) simulation with WRF-CHEM is quite challenging task [3], however, the TROPOMI data was crucial to identify modeling problems in areas with absence of air quality data, indicating possible adjustments and corrections in the emissions inventories.

[1]        Gao, S., et al., 2021, Atmospheric formaldehyde, glyoxal and their relations to ozone pollution under low- and high-NOx regimes in summertime Shanghai, China, Atmospheric Research, https://doi.org/10.1016/j.atmosres.2021.105635

[2]        Freitas & Fornaro, 2022, Atmospheric Formaldehyde Monitored by TROPOMI Satellite Instrument throughout 2020 over São Paulo State, Brazil, Remote Sensing, https://doi.org/10.3390/rs14133032

[3]        Peralta, A., et al., 2023, Future Ozone Levels Responses to Changes in Meteorological Conditions under RCP 4.5 and RCP 8.5 Scenarios over São Paulo, Brazil., Atmosphere, https://doi.org/10.3390/atmos14040626

[4] CETESB < https://cetesb.sp.gov.br/ar/wp-content/uploads/sites/28/2023/07/Relatorio-de-Qualidade-do-Ar-no-Estado-de-Sao-Paulo-2022.pdf>

Keywords:  BIOMASP; Formaldehyde; TROPOMI; WRF-CHEM

How to cite: Zacharias, D., Freitas, A., Borbon, A., Ynoue, R., and Fornaro, A.: Comparison between Sentinel 5P and WRF-CHEM long-term simulations: An analysis based on TROPOMI HCHO data over São Paulo, Brazil within the BIOMASP+ project, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-13764, https://doi.org/10.5194/egusphere-egu24-13764, 2024.

Aviation is a vulnerable infrastructure. This is not only true during economic crises such as the COVID-19 pandemic but also during natural hazards, especially airborne ones. Airborne hazards can be detected and observed by Earth Observation (EO) instruments. Most EO sensors that observe air pollutants fly on Sun-synchronous satellites. The strength of these satellites is global coverage and provision of high spatial resolution measurements. Their disadvantage is, that they do not observe high temporal variations of air pollutants. This is a severe limitation for the detection of natural hazards. One solution is to combine observations from Sun-synchronous (e.g., OMI, GOME2, TROPOMI, IASI, OMPS, AIRS) and geostationary (e.g., MSG-SEVIRI for Europe and Africa) instruments.

The Volcanic Ash Advisory Centers (VAACs) are responsible for predicting the dispersion of the volcanic plumes for the aviation sector. In addition, GeoSphere Austria supports the Austrian aviation authority (Austro Control) with information on volcanic ash and SO₂ dispersion generated by the GeoSphere Austria emergency response Volcano Tool (GeoSphere Austria-VT). Since dispersion information needs to be available shortly after the eruption, VAACs and GeoSphere Austria forecasts are both based on rough estimates of source term parameters. The usage of near-real-time observations can significantly improve the source terms, and reduce the dispersion uncertainty. The GeoSphere Austria-VT is extended with a dynamic inverse modelling system that provides sequentially updated source terms using satellite data.

Apart from flying through volcanic plumes resulting possibly in a significant hazard, flying through regions with elevated air pollution levels has an impact on engine lifetime, maintenance costs, and fuel consumption. Here, the relevant factor is the cumulative air pollution intake over time. Additional costs associated with maintenance and repair are currently not considered in flight planning. Continuous monitoring, forecasting, and optimizing data integration of air pollutants into atmospheric models has thus two significant advantages: on the one hand, the obvious risk associated with flying through highly polluted air (including volcanic ash and SO₂) is reduced, on the other hand, the impact on engine maintenance and fuel costs for airline operators and engine manufacturers is minimized. From the wide range of air pollutants, we will focus on aerosols (volcanic, dust and salt) and SO₂, because these are the most relevant air pollutants for the aviation sector.

The aim is to implement a flexible, holistic system that is able to consider both hazardous and non-hazardous air pollution levels. The emphasis is on making extensive use of existing services (SACS, CAMS, VAACs) as well as air quality observations from satellites to extend and improve model applications (GeoSphere Austria-VT). To provide end-users with one comprehensive tool for the analysis and comparison of the air pollutants distribution from selected sources, these products will be available and visualized in one new data platform, exploiting a datacube-like approach to deal with the different spatial and temporal resolutions of the data.

How to cite: Hirtl, M., Scherllin-Pirscher, B., Mulder, M. D., Maurer, C., Weissinger, M., Natali, S., Figuera, R. M., Rendl, C., Rokitansky, C.-H., Zobl, F., Marschallinger, R., Faber, R., and Zopp, R.: Integrating EO and Copernicus Atmospheric services into emergency response tools to support flight planning Applications, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-14719, https://doi.org/10.5194/egusphere-egu24-14719, 2024.

Owing to its high spatial resolution, the TROPOspheric Monitoring Instrument (TROPOMI) launched in 2017 onboard the Sentinel-5 Precursor (S5P) platform provides important information on global volcanic and anthropogenic SO₂ emissions, with an unprecedented level of details.

In a recent study (Theys et al., 2021), we proposed an approach called Covariance-Based Retrieval Algorithm (COBRA), different from the classical Differential Optical Absorption Spectroscopy (DOAS). Application of COBRA to TROPOMI SO₂ column retrievals leads to a significant reduction of the retrieval noise and biases as compared to the TROPOMI operational (DOAS-based) SO₂ product. COBRA even reveals new emission sources in long-term averaged SO₂ maps.

In view of a future operational deployment (planned end 2024), the COBRA SO₂ scheme is being implemented as part of the Copernicus S5-P Product Algorithm Laboratory (PAL). In this poster, we give an update of TROPOMI COBRA SO₂ results. The latest developments of COBRA S5P-PAL v2 algorithm are presented and discussed. The pre-operational S5P-PAL environment enables a full reprocessing of TROPOMI data. For several examples, we illustrate the COBRA data set for the long-term monitoring of SO₂ columns over both anthropogenic and volcanic scenes. Finally, possible future developments of COBRA are discussed.

Theys, N., Fioletov, V., Li, C., De Smedt, I., Lerot, C., McLinden, C., Krotkov, N., Griffin, D., Clarisse, L., Hedelt, P., Loyola, D., Wagner, T., Kumar, V., Innes, A., Ribas, R., Hendrick, F., Vlietinck, J., Brenot, H., and Van Roozendael, M.: A Sulfur Dioxide Covariance-Based Retrieval Algorithm (COBRA): application to TROPOMI reveals new emission sources, Atmos. Chem. Phys., 21, 16727–16744, https://doi.org/10.5194/acp-21-16727-2021, 2021.

How to cite: Theys, N., Vlietinck, J., Yu, H., De Smedt, I., Fabris, L., Brenot, H., van Gent, J., Niemeijer, S., Romahn, F., Hedelt, P., Loyola, D., and Van Roozendael, M.: Advanced retrieval of sulfur dioxide from TROPOMI using COBRA, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-15017, https://doi.org/10.5194/egusphere-egu24-15017, 2024.

About 10% of the total amount of ozone resides in the troposphere, which acts as a potent greenhouse gas. Anthropogenic emissions and biomass burning are the main sources of ozone in the troposphere, and overexposure to this pollutant causes health problems and damages vegetation.

A combination of space-borne limb and nadir measurements in the UV-visible spectral range (so-called limb-nadir matching, LNM) provides valuable information on tropospheric ozone. This study uses data from the SCanning Imaging Absorption spectroMeter for Atmospheric CartograpHY (SCIAMACHY) (2002-2012) and Ozone Mapping and Profiler Suite on board of Suomi National Polar-Orbiting Partnership (OMPS/NPP, since 2012). Both instruments observe the atmosphere in both limb and nadir geometry. Tropospheric ozone columns are retrieved globally by subtracting the stratospheric ozone column calculated from limb observations from the total ozone column derived from the nadir measurements.

Tropospheric ozone retrievals use different upper altitude limits to calculate the tropospheric ozone column. In the case of the LNM technique, the upper limit is defined by the thermal and/or dynamical tropopause. The Convective Clouds Differential technique (CCD) calculates the tropospheric ozone column up to 270 hPa. Phase II of the Tropospheric Ozone Assessment Report (TOAR-II) uses different pressure levels for different latitudes as an upper limit for the tropospheric column.

After updating and improving the SCIAMACHY-LNM and the OMPS/NPP-LNM datasets, we obtained a long-term dataset of tropospheric ozone (2002-2023) by merging them. Here, we present this new long-term LNM tropospheric ozone column dataset, which has been converted to the different definitions of column heights as prescribed in TOAR II. The datasets are validated using ozonesondes, and the results for the different column definitions are evaluated and discussed.

How to cite: Orfanoz-Cheuquelaf, A., Arosio, C., Rozanov, A., Weber, M., and Burrows, J.: Long-term tropospheric ozone from SCIAMACHY+OMPS and effects of the upper limit definition of the column, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-16562, https://doi.org/10.5194/egusphere-egu24-16562, 2024.

A Pandora spectrometer has been installed on the roof of the laboratory building of the Aerospace Information Research Institute of the Chinese Academy of Sciences in the Olympic Park, Beijing, China, in August 2021. The concentrations of trace gases (including NO₂, HCHO, O₃) measured with Pandora are made available through the open-access Pandora data base (https://data.pandonia-global-network.org/Beijing-RADI/Pandora171s1/). The Beijing-RADI Pandora is included in the data suite which is routinely used for TROPOMI S5P validation. The use of Pandora total and tropospheric NO₂ VCDs for validation of collocated TROPOMI data, resampled to 100×100 m², shows that although on average the TROPOMI VCDs are slightly lower, they are well within the expected error for TROPOMI. The location of the Pandora instrument within a sub-orbital TROPOMI pixel of 3.5×5.5 km² may result in an error in the TROPOMI-derived tropospheric NO₂ VCD between 0.223 and 0.282 Pmolec.cm^-2, i.e., between 1.7% and 2%. In addition, the data also show that the Pandora observations at the Beijing-RADI site are representative for an area with a radius of 10 km.

The Pandora total and tropospheric NO₂ vertical column densities (VCDs) and surface concentrations collected during the first year of operation show that NO₂ concentrations were high in the winter and low in the summer, with diurnal cycle where the concentrations reach a minimum during day time. The concentrations were significantly lower during the 2022 Winter Olympics in Beijing, showing the effectiveness of the emission control measures during that period. The Pandora observations show that during northerly winds clean air is transported to Beijing with low NO₂ concentrations, whereas during southerly winds pollution from surrounding areas is transported to Beijing and NO₂ concentrations are high. The contribution of tropospheric NO₂ to the total NO₂ VCD varies significantly on daily to seasonal time scales, i.e., monthly averages vary between 50% and 60% in the winter and between 60% and 70% in the spring and autumn. The comparison of Pandora-measured surface concentrations with collocated in situ measurements using a Thermo Scientific 42i-TL Analyzer shows that the Pandora data are low and that the relationship between Pandora-derived surface concentrations and in situ measurements are different for low and high NO₂ concentrations. Explanations for these differences are offered in terms of measurement techniques and physical (transport) phenomena.

How to cite: de Leeuw, G., Liu, O., Li, Z., Lin, Y., Fan, C., Zhang, Y., Li, K., Zhang, P., Wei, Y., Chen, T., and Dong, J.: Interpretation of Pandora NO2 measurements over Beijing and application to satellite validation, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-17891, https://doi.org/10.5194/egusphere-egu24-17891, 2024.

Tropospheric NO₂, one of the major atmospheric pollutants, is harmful to human health and plays an important role in atmospheric chemistry. Tropospheric NO₂ concentration is controlled by anthropogenic emission and meteorological conditions, such as solar radiation and humidity. In early 2020, unprecedented lockdowns and travel bans were implemented in China to fight COVID-19, leading to a large decrease of NO₂ compared with preceding years. To isolate the effects of anthropogenic emission and weather, we applied a linear regression model between satellite observed NO₂ column density and meteorological variables. Compared with 2017, it is found that atmospheric NO₂ in 2020 changed -37.8 ± 16.3 %, with the contribution of weather +8.1 ± 14.2 % and anthropogenic emission -49.3 ± 23.5 %. Similar results were also found in 2018 and 2019, revealing that the effect of reduced emission on atmospheric NO₂ is counteracted by the weather, and is actually larger than the observation. The simulations by GEOS-Chem model also supported the results in typical regions. The reduction of NO₂ induced by anthropogenic emission can be well explained by human mobility, showing significantly negative correlations to migration indices provided by Baidu Location-Based-Service, particularly that inside the city. The intra-city migration index can explain 40.4 ± 17.7 % variance of the emission-induced reduction of NO₂ in 29 megacities, each of which has a population of over 8 million in China.

How to cite: Zhang, Y.: Tropospheric NO2 in China during the COVID-19 lock-down is largely decreased due to the controlled human mobility, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-17976, https://doi.org/10.5194/egusphere-egu24-17976, 2024.

Quantification of NO2 from different sectors of economic activity remains critical to monitor air pollutants with the rapid development of infrastructures and the rapid industrialization of emerging economies. This study aims to estimate NO2 emissions using satellite NO2 measurements from TROPOMI from different activity sectors over northern Egypt using a full-chemistry atmospheric transport model (WRF-Chem, including aerosol chemistry) and a non-linear Bayesian method. Our top-down approach was carried out for two months, January and July 2022, to analyse the seasonal variations in NO2 emissions over the studied region. The major source of uncertainties in our top-down emission estimates is due to missing sources in the prior emissions (fossil fuel inventory),  lacking more frequent updates and sub-monthly information. We also explore other sources of errors, such as the level of uncertainty used for calculating error covariance factors, the estimation of biogenic emissions, the selection of a quality assurance filter of TROPOMI NO2 and the use of regularization parameters. Non-linearities are included in our optimization algorithm by performing sensitivity experiments with the direct chemistry model (error propagation) to establish daily relationships between NO2 fluxes and concentrations. Our Bayesian inversion produces optimized values over sub-regions of Egypt and for specific sectors. We defined several subregions and assessed the regional NO2 emissions. The total estimated NO2 emissions from the studied region are about 45 Kt for the month of January 2022 and 32 Kt for the month of July 2022. The results were compared to a previous study using the flux-divergence method, showing a fair agreement for the month of winter (R2=0.67) but disagree in terms of magnitude during summer. We discuss the potential causes for the observed mismatch, which is possibly due to the extreme climate of the region, the availability of satellite observations, and large seasonal variations in the lifetime of NO2.

How to cite: Kudupaje Laxmana, Y., Lauvaux, T., Ciais, P., Kumar, P., Cheliotis, I., Lian, J., and Rey-Pommier, A.: Monitoring of NO2 emissions from space using an aerosol chemistry transport model and a non-linear optimization system, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-19024, https://doi.org/10.5194/egusphere-egu24-19024, 2024.

The PRIMARY project is co-funded by the Italian Space Agency (ASI – “Tor Vergata” University of Rome Agreement n. 2022-3 U.0); the project is part of the ASI’s program “PRISMA Scienza”.

How to cite: De Santis, D., Sasidharan, S. T., Di Giacomo, M., Bencivenni, G., Del Frate, F., Curci, G., Amarillo, A. C., Barnaba, F., Di Liberto, L., Pasqualini, F., Bassani, C., Scifoni, S., Casadio, S., Cofano, A., Cardaci, M., and Licciardi, G.: AI and physical models for air quality monitoring at urban scale with PRISMA hyperspectral data, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-19760, https://doi.org/10.5194/egusphere-egu24-19760, 2024.

The ESA Climate Change Initiative (CCI) Ozone and Aerosols Precursors project is developing long-term climate data records (CDRs) of the Global Climate Observing System (GCOS) Precursors for Aerosol and Ozone Essential Climate Variables. These precursors include short-lived atmospheric trace gases such as formaldehyde (HCHO), glyoxal (CHOCHO), nitrogen dioxide (NO2), sulphur dioxide (SO2), carbon monoxide (CO), and ammonia (NH3). The project aims to create consistent and harmonized CDRs from multiple satellite missions, including GOME, SCIAMACHY, GOME-2, OMI, TROPOMI, IASI, and MOPITT.

This work presents selected findings of a round robin exercise conducted for UV-VIS retrievals. We focus on two key factors that influence HCHO air mass factor determination: the surface albedo climatology and the model a priori profiles. The impact of these factors on the HCHO vertical columns is evaluated by comparing the use of recent auxiliary datasets. Results are presented for TROPOMI HCHO columns and compared to the operational product.

The recent reprocessing of TROPOMI Level 1 data has enabled the development of new albedo climatologies in the UV, offering a finer spatial resolution than the previously used OMI albedo climatology. Additionally, we evaluate the use of a priori vertical profiles from the CAMS reanalysis dataset (spanning the 2003-2022 period) instead of the current TM5-MP profiles used in the TROPOMI operational product. We assess the impact of these alternative datasets on the TROPOMI HCHO vertical columns and on their validation towards ground-based data.

The generation of the ESA CCI HCHO CDR will be based on these findings. This comprehensive assessment not only contributes to the ongoing improvement of TROPOMI data quality but also provides deeper insights into the factors influencing HCHO vertical columns.

How to cite: De Smedt, I., Yu, H., Theys, N., Heue, K.-P., Compernolle, S., Pinardi, G., Hedelt, P., Tilstra, G., Danckaert, T., Vigouroux, C., Langerock, B., Loyola, D., Richter, A., Boersma, F., and Van Roozendael, M.: Assessment of TROPOMI HCHO Vertical Columns: evaluating the use of CAMS vertical profiles and new TROPOMI surface albedo climatologies for air mass factor determination, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-20191, https://doi.org/10.5194/egusphere-egu24-20191, 2024.

The Tropospheric Emissions: Monitoring of Pollution (TEMPO) satellite was launched in April 2023 by NASA and has been measuring tropospheric trace gases with hourly time resolution over North America since August 2023. The geostationary orbit of TEMPO poses advantages and also some new challenges to satellite validation efforts (e.g., due to changes in geometry, stratospheric correction, and the spatial scales of sampling) that remain understudied. Overlapping with TEMPO’s early measurement phase, the University of Colorado Airborne Multi-Axis Differential Optical Absorption Spectroscopy (CU AMAX-DOAS) instrument was deployed to probe tropospheric NO2 and other trace gas columns during research flights over New York City, NY conducted as part of the Coastal Urban Plume Dynamics Study (CUPiDS) from July 15 to August 15, 2023. CU AMAX-DOAS is co-deployed with a NOAA Doppler lidar, two 4-channel radiometers (surface albedo), and in situ measurements onboard the NOAA Twin Otter aircraft, with the objectives to better understand emissions and meteorology as drivers for air quality in coastal Metropolitan areas. This presentation focuses on the inter-comparison of tropospheric NO2 trace gas columns from TEMPO and AMAX-DOAS remote sensing measurements. 

How to cite: Volkamer, R., Lee, C., Mesburis, R., Silver, C., Reza, M., Brewer, A., Brown, S., McDonald, B., Zuraski, K., and Baidar, S.: Evaluating TEMPO NO2 over the New York City Metropolitan Area during CUPiDS, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-20818, https://doi.org/10.5194/egusphere-egu24-20818, 2024.

Lightning is the dominant source of nitrogen oxides (NO_x) in the free troposphere. Yet, its representation in models is highly parameterised, limiting our ability to determine past and future changes in lightning NO_x and causing errors in model representation of tropospheric ozone and NO_x. Models such as GEOS-Chem use fixed lightning NO_x production rates constrained with historic satellite instrument observations of ozone. A new approach is to model NO_x production per flash (mol N fl^-1) using lightning energy dependent NO_x yields and lightning flash radiant energy data from the space-based lightning imaging sensor (LIS) aboard both the Tropical Rainfall Measuring Mission (TRMM) satellite and the International Space Station (ISS). This updated approach is then used in GEOS-Chem to compute total lightning NO_x yields through the Harmonized Emissions Component (HEMCO), rather than using fixed values. The updated annual lightning NO_x emissions total 6.5 Tg N, similar to the original parameterised representation (5.8 Tg N), but with much greater variability in NO_x production rates. The original implementation uses 260 mol N fl^-1 everywhere except the northern extratropics that are at 500 mol fl^-1. In the updated implementation, values range from 27 to 632 mol N fl^-1 over the ocean and from 66 to 482 mol N fl^-1 over land. Greater values over the ocean are due to oft-reported much more energetic maritime lightning. To test the effect on tropospheric ozone and NO_x, we are currently comparing seasonal mean GEOS-Chem and TROPOMI-derived vertical profiles of ozone and NO₂. The TROPOMI-derived values, obtained by cloud-slicing partial columns over optically thick clouds, we have previously evaluated to be consistent with NASA DC-8 aircraft measurements in the free troposphere for cloud-sliced NO₂ (differences < 20 pptv) and the global ozonesonde network for cloud-sliced ozone across the whole troposphere (differences < 35 ppbv). This offers the means to assess the representation of lightning NO_x and better understand its influence on tropospheric NO_x and ozone.

How to cite: Horner, R., Marais, E., and Wei, N.: Improved lightning NOx emission inventory evaluated with vertical profiles of NO2 and ozone obtained by cloud-slicing TROPOMI  , EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-8441, https://doi.org/10.5194/egusphere-egu24-8441, 2024.

South Asia, with its high population density supported by thriving industrial and agricultural sectors, is one of the most polluted region in the world. In early November 2023, the region along the Himalayas, the Indo-Gangetic Plain (IGP), experienced a severe air pollution episode that affected visibility over several thousand kilometers and impacted millions of inhabitants.

Here we use a variety of measurements and datasets to attempt to untangle the reasons behind the formation and the buildup of this pollution episode. Using IASI (Infrared Atmospheric Sounding Interferometer) measurements, embarked on board of the Metop satellites, we find exceptionnally high concentrations of carbon monoxide (CO) and ammonia (NH₃) in the Northwestern states of IGP. Fire satellite measurements from MODIS (Terra and Aqua) and VIIRS (Suomi-NPP and NOAA-20) show that CO is mainly emitted from agricultural waste burning, prevalent at the post-monsoon season. NH₃ primarily emanated from extensive applications of nitrogenous fertilizers, as well as fires, contributing to the formation of fine particulate matter (PM2.5) in the region and degrading the air quality as seen by local air quality stations. ERA5 reanalysis unveiled that these high concentrations of pollutants and their buildup was favored by meteorological conditions that resulted in air mass stagnation, facilitating the accumulation of pollutants in the region.

This study builds a framework to demonstrate the potential of using satellite instruments data, in situ measurements, and reanalysis combined to understand the formation and the progression of air pollution episodes in South Asia.

How to cite: Sinnathamby, S., Safieddine, S., Viatte, C., Hadji-Lazaro, J., George, M., Coheur, P., Clarisse, L., Van Damme, M., and Clerbaux, C.: The November 2023 severe pollution episode in Pakistan and Northern India , EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-10413, https://doi.org/10.5194/egusphere-egu24-10413, 2024.

Copernicus provides a wide variety of services covering different topics, starting from Atmosphere through Marine, Land, Climate Change, Security and Emergency.

Satellite observations on atmospheric composition, complementary to Copernicus Atmosphere Monitoring Service (CAMS), become increasingly available. Unfortunately, analysis or even opening of satellite data in their native formats prove to be challenging in communities other than scientific.

Functionalities, data products, and analysis provided to users on the CAMS website are mainly at the global and European scales. It has been recognized that usage of those services and data they provided by Member States are rather unsatisfactory. Therefore, ECWF prepared CAMS National Collaboration Programmes for member states to improve the uptake of CAMS products at the national, regional and local levels, responding to regulatory needs coming from public administration, NGO's and other interested parties. Institute of Environmental Protection – National Research Institute is responsible for the provision and development of the CAMS National Collaboration Programme for Poland.

We will present the usage of prepared averaged products derived from Sentinel 5P AER AI, Sentinel 5P NO2, and S5P HCHO data in investigating transport episodes connected with wildfires or desert dust over the Polish region. We have investigated data from 2019 to 2023 for both RPRO and OFFL Sentinel 5P products.

We will also discuss the potential usage of other products being tailored and developed during the CAMS NCP Poland project, which have been indicated during the preliminary communication phase via survey  and discussion on 1-st User and stakeholder meeting. The study's outcome would also be important for the HE CAMEO project, where we investigate potential benefits from the assimilation of satellite data to the regional models.

How to cite: Przeździecki, K., Strużewska, J., Kamiński, J., Jeleniewicz, G., Mochocki, D., and Kawka, M.: Enhancing Environmental Monitoring in Poland: Leveraging Sentinel Satellite Data through the CAMS National Collaboration Programme, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-17309, https://doi.org/10.5194/egusphere-egu24-17309, 2024.