Displays

The Copernicus Sentinel 5 Precursor (S5P) is the first of the Sentinel satellites dedicated to the observation of the atmospheric composition, for climate, air quality and ozone monitoring applications. The payload of S5P is TROPOMI (TROPOspheric Monitoring Instrument), a spectrometer covering spectral bands in ultraviolet, visible, near infrared and shortwave infrared, which was developed by The Netherlands in cooperation with the European Space Agency (ESA). TROPOMI has a wide swath of 2600 km, enabling daily global coverage, in combination with a high spatial resolution of about 3.5 x 5.5 km² (7 x 5.5 km² for the SWIR band).

S5P was successfully launched on 13 October 2017 and following a six-month commissioning phase, the operational data stream started at the end of April 2018. All of the TROPOMI operational data products have been released, with the exception of the ozone profile, which is planned to become available with the next major release[AR1]  of the Level 1B data. In addition to the operational data products, new research products are also being developed.

In this contribution, the status of TROPOMI and its data products will be presented. Results for observations of recent events will be provided, along with an outlook on the next release of the data products.

How to cite: Veefkind, P., Aben, I., Dehn, A., Kleipool, Q., Loyola, D., Richter, A., van Roozendael, M., Siddans, R., Wagner, T., Zehner, C., and Level, P.: Sentinel 5 Precursor: Status of TROPOMI and the Operational Data Products, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-6895, https://doi.org/10.5194/egusphere-egu2020-6895, 2020.

We evaluate the satellite-based TROPOMI (TROPOspheric Monitoring Instrument) NO2 products against ground-based observations in Helsinki (Finland). TROPOMI NO2 total (summed) columns are compared with the measurements performed by the Pandora spectrometer during April–September 2018. The mean relative and absolute bias between the TROPOMI and Pandora NO2 total columns is about 10 % and 0.12 × 10¹⁵ molec. cm^-2 respectively. 

We find high correlation (r = 0.68) between satellite- and ground-based data, but also that TROPOMI total columns underestimate ground-based observations for relatively large Pandora NO2 total columns, corresponding to episodes of relatively elevated pollution. This is expected because of the relatively large size of the TROPOMI ground pixel (3.5 × 7 km) and the a priori used in the retrieval compared to the relatively small field-of-view of the Pandora instrument. On the other hand, TROPOMI slightly overestimates relatively small NO2 total columns. Replacing the coarse a priori NO2 profiles with high-resolution profiles from the CAMS chemical transport model improves the agreement between TROPOMI and Pandora total columns for episodes of NO2 enhancement. 

In order to evaluate the capability of TROPOMI observation for monitoring urban air quality, we also analyse the consistency between satellite-based data and NO2 surface concentrations from the local air quality station. We find similar day-to-day variability between TROPOMI and in situ measurements, with NO2 enhancements observed during the same days. Both satellite- and ground-based data show a similar weekly cycle, with lower NO2 levels during the weekend compared to the weekdays as a result of reduced emissions from traffic and industrial activities (as expected in urban sites). The TROPOMI NO2 maps reveal also spatial features, such as the main traffic ways, the airport and other industrial areas, as well as the effect of the prevailing south-west wind patterns. 

These first results confirm that TROPOMI NO2 products are valuable to complement the traditional ground-based in situ data for monitoring urban air quality and are already tested by local and national authorities as well as private companies to monitor pollution sources in the Helsinki region (e.g., emissions from traffic, energy production or oil refineries). For example, TROPOMI NO2 products are already used by the oil refinery company NESTE in their sustainability report and by the Finnish Ministry of Environment to map the air pollution levels in Finland.

Ialongo, I., Virta, H., Eskes, H., Hovila, J., and Douros, J.: Comparison of TROPOMI/Sentinel 5 Precursor NO2 observations with ground-based measurements in Helsinki, Atmos. Meas. Tech. Discuss., https://doi.org/10.5194/amt-2019-329, accepted for publication, 2020.

How to cite: Ialongo, I., Virta, H., Eskes, H., Hovila, J., and Douros, J.: Comparison of TROPOMI/Sentinel-5 Precursor NO2 product with ground-based observations in Helsinki and first societal applications, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-9963, https://doi.org/10.5194/egusphere-egu2020-9963, 2020.

Nitrogen oxides (NO _x = NO + NO₂) in the upper troposphere (~10-12 km) are effective at producing ozone in the upper troposphere where ozone is a potent greenhouse gas. Observations of NO_x in the upper troposphere are limited in time to a few intensive research aircraft campaigns and in space to commercial aircraft campaigns. There are satellite-derived observations of NO₂ in the upper troposphere from the Ozone Monitoring Instrument (OMI), but these are at very coarse resolutions (seasonal, > 2,000 km). The high-resolution Sentinel-5P/TROPOMI instrument offers higher spatial resolution and better cloud-resolving capability than OMI. Here we use synthetic columns of NO₂ from the GEOS-Chem chemical transport model to assess feasibility of deriving NO₂ in the upper troposphere using partial columns of NO₂ above cloudy scenes (the so-called cloud-slicing technique). The model is also used to quantify errors induced by uncertainties in cloud-top height and to determine whether NO₂ over cloudy scenes is representative of all-sky conditions (the "truth"). We find that the cloud-slicing approach is spatially consistent (R =0.5) with the "truth", but with a small (10 pptv) bias in background NO₂. Cloud-slicing is then applied to TROPOMI total columns of NO₂ to derive near-global observations of NO₂ in the upper troposphere and assessed against the existing OMI products and aircraft observations from NASA DC8 aircraft campaigns.

How to cite: Marais, E., Joiner, J., and Choi, S.: First estimate of NO2 in the upper troposphere from TROPOMI , EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-14709, https://doi.org/10.5194/egusphere-egu2020-14709, 2020.

Economic development and rapid urbanization have increased the consumption of fossil fuel in megacities degrading the local air quality. Burning efficiency is a major factor determining the impact of fuel burning on the environment. It varies with environmental conditions and influences the ratio at which pollutants are emitted, as expressed by the emission factor. Emission factors are an important source of uncertainty in global emission inventories.

To improve the quantification of burning efficiency and emission factors, this study investigates co-located NO₂ and CO satellite retrievals from TROPOMI over the megacities of Tehran, Mexico City, Cairo, Riyadh, Lahore and Los Angeles. The TROPOMI instrument was successfully launched by the European Space Agency on 13 October, 2017. It measures atmospheric trace gases with daily coverage and a spatial resolution of 7x7 km². At this resolution, TROPOMI detects hotspots of CO and NO₂ pollution over megacities in single satellite overpasses. The Upwind Background and Plume rotation methods are applied to quantify and evaluate TROPOMI derived ∆NO₂/∆CO ratios. TROPOMI derived ∆NO₂/∆CO ratios show a strong correlation (r = 0.85 and 0.7) with emission ratios from the Emission Database for Global Atmospheric Research (EDGAR v4.3.2) and Monitoring Atmospheric Chemistry and Climate and CityZen (MACCity) 2018, with the highest ratio for Riyadh and lowest for Lahore. Inventory-derived emission ratios are larger than TROPOMI-derived total column ratios by 60 to 80%. As we will show, this can largely be explained by the limited lifetime of NO₂ and the different vertical sensitivity of the TROPOMI NO₂ and CO column retrievals. Taking this into account, TROPOMI retrieved emission ratios are generally within 10 to 25% of MACCity. However, larger differences, up to 80%, are found with EDGAR. For Los Angeles, both inventories overestimate NO2/CO ratios compared with TROPOMI. Validation using the air quality monitoring network of Los Angeles supports the lower ∆NO₂/∆CO ratios inferred from TROPOMI, indicating that burning efficiencies in Los Angeles are indeed poorer than indicated by the inventories.

How to cite: Lama, S., Houweling, S., Boersma, F., Aben, I., Denier van der Gon, H., Krol, M., Dolman, A. J. (., Borsdorff, T., and Lorente, A.: Quantifying burning efficiency in Megacities using NO2/CO ratio from the Tropospheric Monitoring Instrument (TROPOMI), EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-4814, https://doi.org/10.5194/egusphere-egu2020-4814, 2020.

The Sentinel-5 Precursor (S-5P) spectral radiance measurements in the shortwave-infrared (SWIR) spectral region permit the retrieval of atmospheric methane (CH₄) and carbon monoxide (CO) columns with high spatial resolution and nearly daily coverage. Methane is an important greenhouse gas with increasing atmospheric concentrations contributing to global warming. Carbon monoxide is an air pollutant with emissions originating from, for example, fossil fuel combustion and biomass burning. We have adjusted and optimized the scientific retrieval algorithm WFM-DOAS to retrieve methane and carbon monoxide columns and column-averaged mixing ratios (XCH₄ and XCO) from the S-5P spectra. The retrieval algorithm is based on linear-least squares fitting simulated radiance spectra to the observed spectra. For each single ground pixel we determine a quality flag using a Random Forest based machine learning approach and a similar method is also used to bias correct the retrieved methane columns to enhance the accuracy. We present an overview of the WFM-DOAS retrieval algorithm and resulting initial methane and carbon monoxide scientific data products covering the first two years of the S-5P mission including validation and comparisons with the operational data products. We focus on methane and present details on scenes showing elevated atmospheric concentrations originating from localized emission sources. In particular, we present first results from a method developed to automatically identify methane enhancements originating from localized gas, oil and coal emission sources.

How to cite: Buchwitz, M., Schneising, O., Noel, S., Reuter, M., Vanselow, S., Bovensmann, H., and Burrows, J. P.: Sentinel-5 Precursor methane and carbon monoxide column retrievals and assessments related to localized emission sources, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-7861, https://doi.org/10.5194/egusphere-egu2020-7861, 2020.

The TROPOspheric Monitoring Instrument (TROPOMI) aboard of the Sentinel 5 Precursor (S5P) has provided methane measurements for more than two years. The high accuracy together with the exceptional spatial resolution (7 x 7 km², 7 x 5.2 km² since August 2019) and temporal coverage (daily) of TROPOMI provides a unique perspective on local to regional methane enhancements. In this contribution, we discuss observations of enhanced methane concentrations over the United States. We analyse in detail temporal and spatial variability of methane over wetlands and agricultural areas along the Mississippi river and in Florida. To understand the observed CH4 anomalies regarding both natural and anthropogenic sources and transport at regional scales, we support our analysis with simulations from the GEOS-Chem atmospheric chemistry and transport model. We also investigate the possibility to use other datasets as a proxy for CH4 emissions (e.g. NO2 for agricultural areas, land surface temperature for wetlands). These results are based on an improved TROPOMI methane product that features among others a new bias correction that is fully independent of any reference measurements. The verification of the TROPOMI XCH4 data with ground-based measurements by the TCCON network yields a station-to-station variability of the XCH₄ error below 10 ppb, in agreement with the comparison with the proxy methane product from the Japanese GOSAT and GOSAT-2 missions. The improved TROPOMI methane product is planned as a future update of the operational TROPOMI processor.

How to cite: Lorente, A., Borsdorff, T., aan de Brugh, J., Butz, A., Kumar Sha, M., Langerock, B., F. Lunt, M., Dammers, E., Hasekamp, O., and Landgraf, J.: Detection of methane enhancements over the Eastern United States with improved TROPOMI retrievals, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-16074, https://doi.org/10.5194/egusphere-egu2020-16074, 2020.

The two main sources of CH4 from the agricultural sector are enteric fermentation and manure management systems. Canada uses the IPCC Tier-II methodology to estimate CH4 for its national inventory report of GHG emissions to UNFCCC, which is based on a bottom-up approach using activity data and emission factors obtained through site level experimental measurements. However, because of the presence of wetlands in some agricultural regions, it has been challenging to obtain accurate CH4 emission estimates at a regional scale.

This study explores the usefulness of S5P methane product for verifying methane emission estimates in eastern Ontario agricultural land. We investigated the spatiotemporal variability of total column methane mixing ratio, as well as other detailed data layers in the TROPOMI product, such as averaging kernels and a prior profiles. The spatial temporal patterns of wetland methane emission derived from the global WetCHARTs dataset, and a prior knowledge of livestock distribution in the region, are used to interpret S5P methane product. Results showed that TROPOMI methane product provides great spatiotemporal coverage that can be used to verify CH4 emissions from agricultural landscape. This will be useful to reduce methane estimation uncertainties at the regional and national scales.

How to cite: Liu, J., Desjardins, R., VanderZaag, A., Worthy, D., and worth, D.: Verifying methane emission estimates from agricultural regions in Eastern Ontario using TROPOMI product, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-12584, https://doi.org/10.5194/egusphere-egu2020-12584, 2020.

The Copernicus Atmosphere Monitoring Service (CAMS, atmosphere.copernicus.eu) led by ECMWF is one of the major users of TROPOMI data. TROPOMI ozone retrievals have been routinely assimilated in the operational CAMS system since December 2018 and help CAMS to provide good quality daily ozone analyses and 5-day forecasts. CO, NO2, HCHO and SO2 retrievals from TROPMI are currently monitored in the operational CAMS system and CH4 in the CAMS GHG system. This means that the data are routinely compared with the CAMS atmospheric composition fields, but do not influence the CAMS analyses yet. Howerver, assimilation tests with TROPOMI CO, NO2, SO2 and CH4 data are ongoing and it is hoped that the routine assimilation of these species in the  CAMS system can begin later this year.

In this presentation we will give an update on the use or TROPOMI data in the CAMS system and show the latest results from the monitoring and asimilation tests carried out with the TROPOMI data by CAMS.

How to cite: Inness, A., Ades, M., Agusti-Parareda, A., Barre, J., Engelen, R., Flemming, J., Garrigues, S., Kipling, Z., Parrington, M., Peuch, V.-H., Ribas, R., and Suttie, M.: The use of TROPOMI retrievals in the operational CAMS forecast and data assimilation system, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-4862, https://doi.org/10.5194/egusphere-egu2020-4862, 2020.

The backscattered light from within the ocean carries information about surface ocean optical constituents, e.g., phytoplankton and the amount of light in the ocean. Global quantified insight in these parameters is important for estimating primary productivity and heat budget, and for a better understanding and modeling of biogeochemical cycles. Atmospheric sensors such as SCIAMACHY and GOME-2 have proven to yield valuable information on phytoplankton diversity, sun-induced marine fluorescence, and the underwater light field. As commonly used for the retrieval of atmospheric trace gases, the oceanic parameters are inferred from differential optical absorption spectroscopy combined with radiative transfer modeling. Within the ESA Sentinel-5p+ Innovation themes, we explore TROPOMI's potential for deriving the diffuse attenuation coefficient, quantification of different phytoplankton groups and the fluorescence signal of phytoplankton. Here we present results on deriving the diffuse attenuation coefficient from the vibrational Raman scattering signal in backscattered radiances measured by TROPOMI. The diffuse attenuation coefficient describes how fast the incoming radiation in the ocean is diminished with depth. Retrieval results in three spectral regions covering the ultraviolet and blue region of the solar spectrum are presented and intercompared. In future, we will explore if information on sources of colored dissolved organic matter and ultraviolet-absorbing phytoplankton pigments can be inferred from these data sets.

How to cite: Oelker, J., Losa, S., Altenburg Soppa, M., Richter, A., and Bracher, A.: TROPOMI's potential for ocean applications, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-5269, https://doi.org/10.5194/egusphere-egu2020-5269, 2020.

We present a new total column water vapor (TCWV) retrieval algorithm in the visible blue band for the TROPOspheric Monitoring Instrument (TROPOMI) on board the Sentinel 5 Precursor (S5P) satellite. Retrieving water vapor columns in the blue band has numerous advantages over longer wavelengths. Measurements in the blue band are more sensitive at lower troposphere over oceans due to higher surface albedo at this wavelength band. In addition, no correction for spectral saturation effects is required as water vapor is optically thin in this spectral band. The blue band algorithm uses the differential optical absorption spectroscopic (DOAS) technique to retrieve water vapor slant columns. The measured water vapor slant columns are converted to vertical column using air mass factors (AMFs). The new algorithm has an iterative optimization module to dynamically find the optimal a priori water vapor profile. The dynamic a priori algorithm makes use of the fact that the vertical distribution of water vapor is strongly correlated to the total column. This makes it better suited for climate studies than usual satellite retrievals with static a priori or vertical profile information from chemistry transport model (CTM).

The new algorithm is applied to TROPOMI observations to retrieve TCWV. Due to the long measurement record of GOME-2, the new algorithm is also used to retrieve TCWV from GOME-2. The TCWV data set is validated by comparing to the GOME-2 TCWV operational product retrieved in the red spectral band, MODIS and SSMIS satellite observations. In addition, the new TCWV data set is also compared to ground based sun-photometer and radiosonde measurements. Water vapor columns retrieved in the blue band are in good agreement with the other data sets, indicating that the new algorithm derives precise results. Therefore, it was selected for the S5P Processor Algorithm Laboratory (PAL) project as a future operational product. This algorithm can also be used for the forthcoming Copernicus Sentinel S4 and S5 missions.

How to cite: Chan, K. L., Slijkhuis, S., Valks, P., Köhler, C., and Loyola, D.: Total column water vapor retrieval for TROPOMI/S5P observations in the visible blue band, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-4674, https://doi.org/10.5194/egusphere-egu2020-4674, 2020.

Sentinel-4 and Sentinel-5p instruments provide hyperspectral measurements in UV, VIS and infrared spectral range. Though the main purpose of the satellites is trace gas characterization, both instruments are capable of aerosol and surface characterization. In particular, S4 and S5p measurements in UV have unique information about absorption and elevation properties of aerosol. Moreover, measurements in wide spectral range are very sensitive to aerosol size and surface type. On one hand, aerosol and surface characteristics are important input parameters for different trace gases such as ozone, NO2, BrO, CH2O, H2O, CO2, CO, and CH4. On another hand, aerosol and surface characteristics are very important on their own for climate studies, air pollution and surface monitoring.

The quantitative characterization of aerosol (AOD (Aerosol Optical Depth), aerosol type) and surface properties (BRDF (Bidirectional Reflectance Distribution Function)) from Sentinel-4 and Sentinel-5p instruments is a topic for several ESA/EUMETSAT projects. In particular, in the framework of S5P+I AOD/BRDF project an innovative algorithm will be developed which integrates the advanced GRASP algorithm (Dubovik et al. 2011, 2014) with the heritage AOD and DLER algorithm previously applied to TOMS, GOME(-2), SCIAMACHY and OMI sensors (Tilstra et al., 2017). Innovative GRASP algorithm is expected to provide surface BRDF and AOD with the accuracy required by most trace gas retrieval algorithms.

Here the requirements on aerosol and surface characterization from S4 and S5p instruments will be analyzed. On the basis of inversion results from the synthetic (S4) and real (S5p) measurements we discuss how expected AOD and BRDF accuracy from the innovative and GRASP/S4 algorithms meet these requirements. New advanced possibility of aerosol and surface characterization with GRASP from S5p instrument will be discussed.

References

1. Dubovik, O., et al., “Statistically optimized inversion algorithm for enhanced retrieval of aerosol properties from spectral multi-angle polarimetric satellite observations”, Atmos. Meas. Tech., 4, 975-1018, 2011.
2. Dubovik, O., et al. “GRASP: a versatile algorithm for characterizing the atmosphere”, SPIE: Newsroom, doi:10.1117/2.1201408.005558, Published Online: http://spie.org/x109993.xml, September 19, 2014.
3. Tilstra, L. G., et al., “Surface reflectivity climatologies from UV to NIR determined from Earth observations by GOME-2 and SCIAMACHY”, J. Geophys. Res. Atmos., 122, 4084–4111.

How to cite: Litvinov, P., Dubovik, O., Chen, C., Lopatin, A., Lapionak, T., Fuertes, D., Karol, Y., Holter, C., Lanzinger, V., Bindreiter, L., Hangler, A., De Graaf, M., Tilstra, G., Stammes, P., and Retscher, C.: Surface and aerosol retrieval from S5P and S4: baseline requirements and expected performance, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-19158, https://doi.org/10.5194/egusphere-egu2020-19158, 2020.

Since nearly two years, the operational SO₂ product from the TROPOspheric Monitoring Instrument (TROPOMI) onboard Sentinel-5 Precursor (S5P) platform has provided important information on volcanic and anthropogenic SO₂ emissions, with an unprecedented level of details. In this presentation, we critically discuss the advantages and disadvantages of the current operational algorithm in light of the validation results obtained so far, and present how the retrieval scheme could evolve in the future.

In the first part, we briefly present the main algorithm features and an overview of the SO₂ product validation. One challenge in this respect is the current lack of ground-based SO₂ measurements for anthropogenic source regions. We therefore rely largely on comparisons with other satellite datasets (e.g., OMI and OMPS). The main lesson learnt is that satellite SO₂ retrievals generally agree very well for large SO₂ columns (mostly volcanic) while persisting differences exist for low columns when different algorithms are compared. This motivates the second part of the presentation which aims at extensively comparing the results from existing S5P SO2 operational and scientific algorithms, notably DOAS and PCA retrievals (or other alternative approaches). Here, all configuration settings and auxiliary data (e.g. absorption cross-sections) are aligned in order to better understand the differences through sensitivity tests. This effort is not only important to improve the TROPOMI SO2 results but it is also particularly relevant in the context of the forthcoming Sentinel-4 mission that will mainly probe weak anthropogenic SO₂ sources. The last part of the presentation gives a general overview of new features planned for the next versions of the operational SO₂ algorithm.

How to cite: Theys, N., Li, C., Krotkov, N., De Smedt, I., Lerot, C., Yu, H., Vlietinck, J., Fioletov, V., Hedelt, P., Loyola, D., Wagner, T., and Van Roozendael, M.: TROPOMI SO2 column retrievals: validation, inter-comparison with other satellite data sets and algorithm evolution, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-8861, https://doi.org/10.5194/egusphere-egu2020-8861, 2020.

We present here a novel method for the precise and extremely fast retrieval of volcanic SO2 layer height (LH) based on S5P/TROPOMI data. We have developed the Full-Physics Inverse Learning Machine (FP_ILM) algorithm using a combined principal components analysis (PCA) and neural network approach (NN) to extract the information about the volcanic SO2 LH from high-resolution UV backscatter measurement of TROPOMI aboard Sentinel-5 Precursor.

The SO2 LH is essential for accurate determination of SO2 emitted by volcanic eruptions. So far UV based SO2 plume height retrieval algorithms are very time-consuming and therefore not suitable for near-real-time applications. The FP_ILM approach however enables for the first time to extract the SO2 LH information in a matter of seconds for an entire S5P orbit and thus applicable in NRT application.

The FP_ILM SO2 LH product is developed as part of ESA’s ‘Sentinel-5p+ Innovation - SO2 Layer Height project’ (S5P+I: SO2 LH) project, dedicated to the generation of an SO2 LH product and its extensive verification with collocated ground- and space-born measurements.

How to cite: Efremenko, D., Hedelt, P., Loyola, D., and Spurr, R.: FP_ILM: Extremely fast volcanic SO2 plume height retrieval based on S5P/TROPOMI data using inverse learning machines, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-19452, https://doi.org/10.5194/egusphere-egu2020-19452, 2020.

Since its launch in October 2017, TROPOMI records earthshine radiances in spectral ranges from the ultraviolet to the shortwave infrared regions at an unprecedented spatial resolution (3.5 x 7 km² and 3.5 x 5.5 km² after August 2019). A suite of L2 operational products provide key information for the understanding and monitoring of the Earth-atmosphere system, and more particularly of aspects related to ozone layer protection, air quality and climate change.

The ESA S5p+ Innovation activity aims at further exploiting the capability of the TROPOMI instrument by supporting the development of a number of additional scientific products, including glyoxal tropospheric column retrievals. The latter provide information on VOC emissions as glyoxal is mainly released in the atmosphere as an intermediate product of VOC oxidation, but also directly emitted from biomass burning events.

We present here the BIRA-IASB S5p glyoxal product relying on a DOAS approach and its main features. We show how the large amount of TROPOMI data and its high resolution helps to better identify and localize VOC sources. The many intense fire events that occurred in the last years, e.g. in Northern America in 2018 or in Australia in 2019/2020, led to extreme levels of pollution and unprecedentedly high glyoxal columns are measured accordingly. We also highlight the excellent consistency between the TROPOMI and OMI glyoxal products, allowing thus to combine them in a 15-year data record. The validation of satellite glyoxal retrievals is difficult due to the scarcity of independent data and their own limitations caused by the low glyoxal optical depth. Nevertheless, a few ground-based data sets have been collected and preliminary comparisons with the S5p glyoxal product are presented.

How to cite: Lerot, C., De Smedt, I., Theys, N., Yu, H., Vlietinck, J., Stavrakou, J., Müller, J.-F., Friedrich, M., Hendrick, F., Van Roozendael, M., Alvarado, L., Richter, A., and Retscher, C.: Retrievals of glyoxal tropospheric vertical columns from TROPOMI observations, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-13707, https://doi.org/10.5194/egusphere-egu2020-13707, 2020.

The Copernicus missions Sentinel-4 (S4) and Sentinel-5 (S5) will carry out atmospheric composition observations on an operational long-term basis to serve the needs of the Copernicus Atmosphere Monitoring Service (CAMS) and the Copernicus Climate Change Service (C3S).

Building on the heritage from instruments such as GOME, SCIAMACHY, GOME-2, and OMI, S4 is an imaging spectrometer instruments covering wide spectral bands in the ultraviolet and visible wavelength range (305-500nm) and near infrared wavelength range (750-775 nm). S4 will observe key air quality parameters with a pronounced temporal variability by measuring NO₂, O₃, SO₂, HCHO, CHOCHO, and aerosols over Europe with an hourly revisit time.

A series of two S4 instruments will be embarked on the geostationary Meteosat Third Generation-Sounder (MTG-S) satellites. S4 establishes the European component of a constellation of geostationary instruments with a strong air quality focus, together with the NASA mission TEMPO and the Korean mission GEMS.

This paper will address the development status of the L1b Operational Processor (L1OPS) by EUMETSAT and the supporting L1b reference processor (L1RP) developed by ESA; In dedicated cases (e.g. CTI, Non-linearity signal loss, ...) the algorithms input from the S4 Industrial Prime have been used. The paper will also provide an overview of the status of the Level 2 processor developed by ESA for integration into the EUMETSAT MTG-S ground segment.

How to cite: Bazalgette Courrèges-Lacoste, G., Wright, N., Veihelmann, B., Ahlers, B., Le Rille, O., Gimeno Garcia, S., and Dobber, M.: The Copernicus atmospheric Mission Sentinel-4: Status of algorithm developments for the L1b and L2 processors, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-7027, https://doi.org/10.5194/egusphere-egu2020-7027, 2020.

European UVN satellite missions deliver global measurements for air quality and climate applications from Low Earth Orbit (LEO) satellites since over two decades. Currently we have in the morning data from GOME-2 on the three MetOp satellites and in the early afternoon data from OMI/Aura and TROPOMI/Sentinel-5 Precursor.

The temporal barrier imposed by LEO satellites, providing only one daily observation, can be broken using Geostationary Equatorial Orbit (GEO) satellites. The Sentinel-4 (S4) mission on-board the MTG-S GEO satellite will focus on monitoring of trace gas column densities and aerosols over Europe with an hourly revisit time, thereby covering the diurnal variation of atmospheric constituents.

We present the algorithm, verification, and processor work being performed as part of the ESA Sentinel-4 Level 2 (S4-L2) project responsible for developing the operational S4-L2 products: O₃ total and tropospheric column, NO₂ total and tropospheric column, SO₂, HCHO, CHOCHO columns, aerosol and cloud properties as well as surface reflectance.

How to cite: Loyola, D., Aspetsberger, M., Dubovik, O., Fantin, D., Govaerts, Y., Richter, A., Van Roozendael, M., Siddans, R., Veefkind, P., Veihelmann, B., Wagner, T., and Wright, N.: Breaking the temporal barrier in air quality monitoring over Europe with Sentinel-4, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-12167, https://doi.org/10.5194/egusphere-egu2020-12167, 2020.

Satellite measurements of tropospheric or total column trace gas species, including those from Sentinel-5p TROPOMI, are affected by the presence of clouds. Therefore, cloud data products retrieved with the same sensor play an essential role, as they allow the data provider to take an estimated cloud impact on the trace gas retrieval into account. Examples are the modification of the radiative transfer and associated quantities such as the air mass factor, and the partial masking of the measurement scene. Evidently, the accuracy of these corrections relies on the accuracy of the retrieved cloud properties, like radiometric cloud fraction (CF), cloud top height (CTH) or cloud height (CH), and cloud optical thickness (COT) or cloud albedo (CA).

We consider here three S5p TROPOMI-based cloud products: (i) L2_CLOUD OCRA/ROCINN CAL (Optical Cloud Recognition Algorithm/Retrieval of Cloud Information using Neural Networks; Clouds-As-Layers), (ii) L2_CLOUD OCRA/ROCINN CRB (Clouds-as Reflecting Boundaries), and (iii) the S5p support product FRESCO-S (Fast Retrieval Scheme for Clouds from Oxygen absorption bands). These are input to the S5p operational processors for several trace gas products, including ozone columns and profile, total and tropospheric NO2, formaldehyde, sulfur dioxide. The quality assessment of these cloud products is carried out within the framework of ESA’s Sentinel-5p Mission Performance Centre (MPC) with support from AO validation projects focusing on the respective trace gases.

In this work, cloud height (from S5p CLOUD CRB and S5p FRESCO algorithms) and cloud top height (from S5p CLOUD CAL) S5p data is validated with radar/lidar-based cloud profile information from the ground-based networks CLOUDNET and ARM at 17 sites. For some sites the comparison is difficult due to e.g., orography or snow/ice cover. S5P and CLOUDNET report similar cloud height variations at several sites, and the correlation between the S5p cloud products and CLOUDNET can be high (Pearson R up to 0.9). However, there is a site-dependent negative bias of the S5p cloud (top) height with respect to the CLOUDNET data: up to -2.5 km for S5p CLOUD CAL cloud top height and -1.5 km for S5p CLOUD CRB and S5p FRESCO cloud height. The dependence on other parameters measured by S5p and CLOUDNET (e.g., radiometric cloud fraction, cloud phase,…) is investigated.

How to cite: Compernolle, S., Argyrouli, A., Lutz, R., Sneep, M., Granville, J., Hubert, D., Keppens, A., Verhoelst, T., Fjaeraa, A. M., Loyola, D., O'Connor, E., and Lambert, J.-C.: Validation of Sentinel-5p retrieved cloud height data using ground-based radar/lidar measurements from the CLOUDNET network, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-7989, https://doi.org/10.5194/egusphere-egu2020-7989, 2020.

How to cite: Sihler, H., Beirle, S., Borger, C., and Wagner, T.: MICRU effective cloud fractions for S-5P/TROPOMI, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-8380, https://doi.org/10.5194/egusphere-egu2020-8380, 2020.

To reduce green house gases emissions, it is crucial to be able to give actionable feedback to industrial facility operators on their emissions. For this purpose GHGSat is building a constellation of satellites capable of monitoring and quantifying emissions from individual sites.

In 2016, GHGSat launched a demonstration satellite called GHGSat-D. It is the first and only satellite able to retrieve the methane column with a spatial resolution of less than 50 meters. We will present examples of detection and quantification of methane leaks in Central Asia using GHGSat-D. The retrieved methane column density shows plumes originating from known source locations and aligned with the local wind direction.  The largest and most persistent of those sources was estimated to have an emission rate of 10-42 tons.h-1, a magnitude comparable to the Aliso Canyon and Ohio blowouts. The complementarity of GHGSat's observations with other satellites observations will be highlighted using a comparison of GHGSat-D and Sentinel-5P in the same Central Asia region.

We will provide an update of GHGSat's constellation, with news from GHGSat-C1 (launch March 2020) and GHGSat-C2 (launch summer 2020). Lessons learned and improvements to the new satellites will be discussed. The anticipated vertical column density precision of GHGSat-C1 and C2 are 2% and 1% of background methane concentration respectively, compared to 13% for GHGSat-D. We will also introduce  the data calibration and validation plans for the new satellites.

How to cite: Strupler, M., Jervis, D., McKeever, J., Varon, D., Gains, D., Tarrant, E., Maasakkers, J. D., Pandey, S., Houweling, S., Aben, I., Scarpelli, T., Jacob, D. J., and Germain, S.: Meter-scale retrieval of industrial methane emission using GHGSat’s satellite constellation, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-11184, https://doi.org/10.5194/egusphere-egu2020-11184, 2020.

In this contribution, we present the Twin ANthropogenic Greenhouse Gas Observers (TANGO) mission, which is one of four candidate missions of ESA’s SCOUT program for the rapid prototyping and demonstration of observation techniques and science application using small-satellites. Over the period 2024-2027, TANGO will provide the unique opportunity for the global and independent monitoring of the major emission sources of the anthropogenic greenhouse gases CH₄ and CO₂. It will demonstrate a distributed monitoring system that can pave the way for future larger constellations of small-satellites allowing for enhanced coverage and temporal resolution. The TANGO mission consists of two agile small-satellites, each carrying one spectrometer flying in conjunction with the Copernicus Sentinel 5 mission. Regular joint TANGO and Sentinel 5 observations will be used to enhance the radiometric accuracy of the TANGO spectrometers. The first satellite measures spectral radiances in the shortwave infrared part of the solar spectrum (1.6 µm) to determine moderate to strong emissions of CH₄ (≥ 10 Kt/yr) and CO₂ (≥ 5 Mt/yr). The instrument has a field of view of 30 x 30 km² at spatial resolutions small enough to monitor individual large industrial facilities (300 x 300 m²), with an accuracy to determine emissions on the basis of a single observation. Using the same strategy, the second satellite yields collocated NO₂ observations from radiance measurements in the visible spectral range, supporting plume detection and exploiting the use of CO₂/NO₂ ratio observations to estimate CO₂ emissions from offshore NO₂ sources. TANGO will provide surface fluxes of specific emission types based on the combination of CH₄, CO₂ and NO₂ observations at a high spatial resolution. In doing so, TANGO aims to uniquely complement the large current and planned Copernicus monitoring missions like Sentinel-5(P) and the CO2M High Priority Candidate Mission (HPCM) by providing unrivalled high-resolution monitoring of the major anthropogenic greenhouse gas emissions at a regular basis.

How to cite: Landgraf, J., Rusli, S., Cooney, R., Veefkind, P., Vemmix, T., de Groot, Z., Bell, A., Day, J., Leemhuis, A., and Sierk, B.: The TANGO mission: A satellite tandem to measure major sources of anthropogenic greenhouse gas emissions, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-19643, https://doi.org/10.5194/egusphere-egu2020-19643, 2020.

Air pollution is responsible for ~7 million premature deaths every year.  Current and planned low Earth orbit and geostationary satellite instruments have long provided global surveys, revealing pollution characteristics and trends.  We need a robust, sustainable observing strategy, however, for measuring the distribution of air pollution at high spatial and high temporal resolution.  The Compact Hyperspectral Air Pollution Sensor (CHAPS) incorporates technologies enabling a sustainable approach to air pollution observation from space.  CHAPS is a hyperspectral imager using freeform optics in a form factor suitable for accommodation on a small satellite or hosted payload.  It will make measurements of air pollution at unprecedented spatial resolution from low Earth orbit (1 x 1 km²) and will characterize, quantify, and monitor emissions from urban areas, power plants, and other anthropogenic activities.  The compact size and relatively lower cost of CHAPS makes a constellation feasible for the first time, with unprecedented spatiotemporal sampling of global point pollution sources.  NASA recently funded the development of a CHAPS–Demonstrator (CHAPS-D), which will result in an airborne demonstration of a CHAPS prototype instrument.  CHAPS derives heritage from the TROPOspheric Monitoring Instrument (TROPOMI) on the Sentinel-5 Precursor, which uses a freeform mirror telescope.  Freeform optics has potentially huge advantages over traditional optical designs, including fewer optical surfaces, less mass and volume, and improved image quality.  CHAPS-D combines a radiometrically calibrated freeform hyperspectral imager (300–500 nm @ 0.5-nm resolution) with associated detector and payload electronics within the design constraints of a 6U CubeSat.  We present the measurement requirements and preliminary design of CHAPS-D.

How to cite: Swartz, W., Krotkov, N., Lamsal, L., Morgan, F., Huang, P., Linden, J., Levelt, P., and Veefkind, P.: CHAPS: A Compact Hyperspectral Imager for Air Pollution Remote Sensing, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-10247, https://doi.org/10.5194/egusphere-egu2020-10247, 2020.

Since its launch in October 2017, the Sentinel-5 Precursor (Sentinel-5P), one of the European Commission’s new Copernicus family – Sentinels, has continuously proven to be successful, enhanced, and upgraded to its predecessor missions. The sole payload on Sentinel-5P is the TROPOspheric Monitoring Instrument (TROPOMI), which is a nadir-viewing 108 degree Field-of-View push-broom grating hyperspectral spectrometer, covering the wavelength of ultraviolet-visible (270 nm to 495 nm), near infrared (675 nm to 775 nm), and shortwave infrared (2305 nm - 2385 nm). Sentinel-5P is currently providing measurements of total column ozone, tropospheric nitrogen dioxide and formaldehyde, sulfur dioxide, methane, carbon monoxide, aerosol index and cloud at very high spatial resolutions. Ozone vertical profile products are scheduled to become available in April 2020. In addition, S5P/TROPOMI spectral design provides the possibility of developing other atmospheric composition products such as BrO, aerosol optical depth, sun-induced fluorescence, etc..

The NASA Goddard Earth Sciences Data and Information Services Center (GES DISC) is one of the 12 Distributed Active Archive Centers (DAACs) within NASA's Earth Observing System Data and Information System (EOSDIS). The GES DISC archives and supports over a thousand data collections in the Focus Areas of Atmospheric Composition, Water & Energy Cycles, and Climate Variability. Under the End User License Agreement between NASA, European Space Agency (ESA) and European Commission (Copernicus Programme), GES DISC is curating S5P/TROPOMI Level-1B and Level-2 products and providing information services through enhanced tools and services that offer convenient solutions for complex Earth science data and applications. This presentation will demonstrate up-to-date TROPOMI products and their applications, as well as various efficient yet straightforward methods to access, visualize and subset TROPOMI data at GES DISC.

How to cite: Zeng, J., Gerasimov, I., Adams, J., Huwe, P., Wei, J., and Meyer, D.: Exploration of Atmospheric Compositions by TROPOMI on Sentinel-5P, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-4330, https://doi.org/10.5194/egusphere-egu2020-4330, 2020.

Tropospheric ozone damages ecosystems and causes human health problems. The high spatial and temporal variability of ozone concentrations in the troposphere challenges global observing systems to monitor ozone at all relevant scales. TROPOMI is a nadir-viewing UV-Vis-NIR-SWIR sensor that combines a high spatial resolution, a large swath width and the spectral measurement characteristics required to deliver trace gas data records at unprecedented detail. The first tropospheric data product was publicly released in Fall 2018, a year after launch on the Sentinel-5p platform (S5p). It is based on the convective-cloud differential technique (CCD) to infer 0.5°x1° resolved daily maps of 3-day moving mean values of the tropospheric ozone column (surface to 270 hPa) between 20°S and 20°N in clear-sky conditions. This makes it the highest resolved tropospheric ozone data set currently available for the tropical belt. About two years of data have been collected since the end of the commissioning phase in April 2018.

We present an assessment of the quality of the Sentinel-5p TROPOMI convective-cloud differential tropospheric ozone column data products (O3_TCL OFFL v01.01.05-01.01.07), carried out within the context of ESA’s Sentinel-5p Mission Performance Center (MPC) and the S5PVT AO project CHEOPS-5p. Our assessment of the first two years of TROPOMI data is based on comparisons with (a) quality-assured co-located in-situ measurements by the SHADOZ ozonesonde network, and, (b) satellite data by the GOME-2 and OMI sensors. These well-characterized observational data records serve as references to evaluate the bias and the dispersion of S5p data, and their dependence on influence quantities. Additional visual inspections of the S5p tropospheric ozone maps unveiled non-geophysical structures introduced by the sampling pattern of sensor and clouds. We conclude by assessing the compliance of S5p tropospheric ozone data with respect to mission and user requirements for key data applications.

How to cite: Hubert, D., Verhoelst, T., Compernolle, S., Keppens, A., Granville, J., Lambert, J.-C., Heue, K.-P., Loyola, D., Eichmann, K.-U., Weber, M., Thompson, A. M., Allaart, M., Piters, A., Johnson, B. J., Selkirk, H. B., Vömel, H., da Silva, F. R., Mohamad, M., Félix, C., and Stübi, R.: Geophysical validation of two years of Sentinel-5p tropical tropospheric ozone columns, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-7720, https://doi.org/10.5194/egusphere-egu2020-7720, 2020.

The Sentinel-5 Precursor (S5P) mission, launched in October 2017, carries the TROPOspheric Monitoring Instrument (TROPOMI), which provides a daily global coverage at a spatial resolution as high as 5.5 km x 3.5 km and will extend the European atmospheric composition record initiated with GOME/ERS-2 in 1995. Due to the ongoing need to understand and monitor the recovery of the ozone layer, as well as the evolution of tropospheric pollution, ozone remains one of the leading species of interest during this mission.

In this work, two and a half years of TROPOMI near real time (NRTI) and offline (OFFL) total ozone column (TOC) products are presented and compared to daily and individual, globally distributed, ground-based quality assured Brewer and Dobson TOC measurements. The daily ground-based ozone measurements used here are deposited in the World Ozone and Ultraviolet Radiation Data Centre (WOUDC). The individual Brewer measurements are made available by the European Brewer Network (Eubrewnet). Furthermore, twilight zenith-sky measurements obtained with ZSL-DOAS (Zenith Scattered Light Differential Optical Absorption Spectroscopy) instruments, which form part of the SAOZ network (Système d’Analyse par Observation Zénitale), are used for the validation.

The quality of the TROPOMI TOC data is evaluated in terms of the influence of various geophysical quantities such as location, solar zenith angle, viewing angle, season, effective temperature, surface albedo and clouds. The overall statistical analysis of the global comparison shows that the mean bias and the mean standard deviation of the percentage difference between TROPOMI and ground-based TOC is within 0 –1.5% and 2.5 %–4.5 %, respectively. Moreover, based on the full available dataset, a first attempt is made for a drift investigation.

Additionally, the TROPOMI OFFL and NRTI products are evaluated against already known spaceborne sensors, namely, the Ozone Mapping Profiler Suite, on board the Suomi National Polar-orbiting Partnership (OMPS/Suomi-NPP), NASA, and the Global Ozone Monitoring Experiment 2 (GOME-2), on board the Metop-A (GOME-2/Metop-A) and Metop-B (GOME-2/Metop-B) satellites. This analysis shows a very good agreement for both TROPOMI products with well-established instruments, with the absolute differences in mean bias and mean standard deviation being below +0.7% and 1%, respectively.

How to cite: Garane, K., Koukouli, M.-E., Verhoelst, T., Lerot, C., Heue, K.-P., Balis, D., Redondas, A., Pazmino, A., Bazureau, A., Romahn, F., Zimmer, W., Xu, J., Lambert, J.-C., Loyola, D., Van Roozendael, M., Goutail, F., and Pommereau, J.-P.: 2.5 years of TROPOMI S5P total ozone column data: geophysical global ground-based validation and inter-comparison with other satellite missions, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-8109, https://doi.org/10.5194/egusphere-egu2020-8109, 2020.

Part of the space segment of EU’s Copernicus Earth Observation programme, the Sentinel-5 Precursor (S5P) mission is dedicated to global and European atmospheric composition measurements of air quality, climate and the stratospheric ozone layer. On board of the S5P early afternoon polar satellite, the imaging spectrometer TROPOMI (TROPOspheric Monitoring Instrument) performs nadir measurements of the Earth radiance within the UV-visible and near-infrared spectral ranges, from which atmospheric ozone profile data are retrieved. Developed at the Royal Netherlands Meteorological Institute (KNMI) and based on the optimal estimation method, TROPOMI’s operational ozone profile retrieval algorithm has recently been upgraded. With respect to early retrieval attempts, accuracy is expected to have improved significantly, also thanks to recent updates of the TROPOMI Level-1b data product. This work reports on the initial validation of the improved TROPOMI height-resolved ozone data in the troposphere and stratosphere, as collected both from the operational S5P Mission Performance Centre/Validation Data Analysis Facility (MPC/VDAF) and from the S5PVT scientific project CHEOPS-5p. Based on the same validation best practices as developed for and applied to heritage sensors like GOME-2, OMI and IASI (Keppens et al., 2015, 2018), the validation methodology relies on the analysis of data retrieval diagnostics – like the averaging kernels’ information content – and on comparisons of TROPOMI data with reference ozone profile measurements. The latter are acquired by ozonesonde, stratospheric lidar, and tropospheric lidar stations performing network operation in the context of WMO's Global Atmosphere Watch and its contributing networks NDACC and SHADOZ. The dependence of TROPOMI’s ozone profile uncertainty on several influence quantities like cloud fraction and measurement parameters like sun and scan angles is examined and discussed. This work concludes with a set of quality indicators enabling users to verify the fitness-for-purpose of the S5P data.

How to cite: Keppens, A., Hubert, D., Lambert, J.-C., Compernolle, S., Verhoelst, T., Niemeijer, S., Fjaeraa, A. M., ter Linden, M., Sneep, M., De Haan, J., and Veefkind, P. and the CHEOPS-5p validation team: Validation of TROPOMI nadir ozone profile retrievals: Methodology and first results, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-7868, https://doi.org/10.5194/egusphere-egu2020-7868, 2020.

We present the results of a project for the Finnish Ministry of the Environment that aimed to assess the potential of satellite measurements in complementing traditional in situ air quality measurements. Co-located NO₂ measurements from the TROPOspheric Monitoring Instrument (TROPOMI) and several traditional air quality stations (measuring in µg/m³) in Finland and Europe between April 2018 and June 2019 are compared to determine their correlation. We find that the correlation of individual air quality stations with TROPOMI is dependent on the location of the station, but is more reliable when all stations in a city centre are studied as a group. This is expected due to the spatial averaging of satellite measurements. We also find that NO₂ measurements between different cities in Finland and Europe in general correlate well.

We also analyse TROPOMI’s and the Ozone Monitoring Instrument’s (OMI) ability to study the spatial distribution of NO₂ over Finland and the Helsinki metropolitan area using gridded maps. Oversampled TROPOMI measurements are able to distinguish relatively small sources such as roads and airports, and the difference in concentrations between weekdays and weekends. TROPOMI is also able to detect emissions from different sources of NO₂ such as cities, mining sites and industrial areas. Long time series measurements from OMI show decreasing NO₂ levels over Finland between 2005 and 2018.

Finally, we convert air quality station measurements to vertical column densities using boundary layer height data, and study the effect that this has on their correlation with TROPOMI measurements.

This study was conducted on behalf of the Finnish Ministry of the Environment, and showcases how satellite measurements can be used reliably alongside traditional air quality measurements to provide a better picture of current pollution levels. Launched in 2017, TROPOMI is currently the highest-resolution air quality sensing satellite, and its societal uses are only beginning to be realized. Future Sentinel missions, especially the geosynchronous Sentinel-4, will provide an even more comprehensive view of the daily air quality situation.

How to cite: Virta, H., Sundström, A.-M., Ialongo, I., and Tamminen, J.: Evaluating the Potential of Satellite Measurements in Air Quality Monitoring: A Project for the Finnish Ministry of the Environment, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-8301, https://doi.org/10.5194/egusphere-egu2020-8301, 2020.

The first European Sentinel satellite for monitoring the composition of the Earth’s atmosphere, the Sentinel 5 Precursor (S5p), carries the TROPOspheric Monitoring Instrument (TROPOMI) on board to map trace species of the global atmosphere at high spatial resolution. Retrievals of tropospheric trace gas columns from satellite measurements are strongly influenced by clouds. Thus, cloud retrieval algorithms were developed and implemented in the trace gas processing chain to consider this impact.

In this study, different cloud products available for NO₂ retrievals from TROPOMI data are analyzed. The TROPOMI level 2 OCRA/ROCINN (Optical Cloud Recognition Algorithm/Retrieval of Cloud Information using Neural Networks) cloud products CRB (cloud as reflecting boundaries) and CAL (clouds as layers) as well as the FRESCO (Fast Retrieval Scheme for Clouds from Oxygen absorption bands) cloud product are compared with regard to e. g. cloud fraction, cloud height, cloud albedo/optical thickness, flagging and quality indicators. In particular, difficult situations such as snow or ice, sun glint, and high aerosol load are investigated.

The eventual aim of this study is to better understand TROPOMI cloud products and their quantitative impacts on trace gas retrievals. Here, we present first results of a statistical analysis on a limited data set comparing currently existing cloud products and their approaches focusing on NO₂.

How to cite: Latsch, M., Richter, A., Burrows, J. P., Wagner, T., Silher, H., van Roozendael, M., Loyola, D., Valks, P., Argyrouli, A., Lutz, R., Veefkind, P., Eskes, H., Sneep, M., Wang, P., and Siddans, R.: Evaluation of TROPOMI cloud products for NO2 retrievals, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-8888, https://doi.org/10.5194/egusphere-egu2020-8888, 2020.

The TROPOspheric Monitoring Instrument (TROPOMI), on board the Sentinel 5 precursor (S5p) satellite, was launched in October 2017. The TROPOMI instrument has high spatial resolution and daily coverage of the Earth. About two years of level 2 data (version 1.1.5/1.1.7) of ozone and cloud properties (fraction and height) are available. Using the OFFL GODFIT ozone and OCRA/ROCINN CRB cloud dataset, we derived tropical tropospheric ozone using the convective cloud differential method for tropical tropospheric column ozone (TTCO) [DU] and the cloud slicing method for upper tropospheric ozone volume mixing ratios (TUTO) [ppbv].

The CCD algorithm was optimized for TROPOMI with respect to the reference sector Above Cloud Column Ozone field (ACCO). It was adjusted in time and latitude space in order to reduce data gaps in the daily ACCO vectors. Also, daily total ozone maps were used to minimize the error in stratospheric ozone differences.

The CHOVA algorithm (Cloud Height induced Ozone Variation Analysis) was developed to fully exploit with the S5p instruments characteristics. A temporal sampling of cloud/ozone data is not necessary for the high amount of S5p measurements. The spatial sampling is 2° latitude/longitude grid boxes. CHOVA results are quality checked based on the statistical properties of cloud, ozone and retrieval parameters to exclude unreliable TUTO values.

Comparisons with ozone sondes show a good agreement for both methods taking into account the principal differences between a sonde point measurement and a satellite sampled mean value. 

The work on TROPOMI/S5P geophysical products is funded by ESA and national contributions from the Netherlands, Germany, Belgium, and Finland.

How to cite: Eichmann, K.-U., Weber, M., Heue, K.-P., and Burrows, J. P.: Ozone in the Tropical Troposphere from Sentinel-5P TROPOMI data: CCD and CSL results, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-9116, https://doi.org/10.5194/egusphere-egu2020-9116, 2020.

The TROPOspheric Monitoring Instrument (TROPOMI) is an UV-VIS-NIR-SWIR instrument on board of Sentinel-5P satellite developed for monitoring the Earth’s atmosphere. It was launched on 13 October 2017 in a near polar orbit. It measures spectrally resolved earthshine radiances at an unprecedented spatial resolution of around 3.5x7.2 km² (3.5x5.6 km² starting from 6 Aug 2019) (near nadir) with a total swath width of ~2600 km on the Earth's surface providing daily global coverage. From the measured spectra high resolved trace gas distributions can be retrieved by means of differential optical absorption spectroscopy (DOAS).

Chlorine dioxide (OClO) is a by-product of the ozone depleting halogen chemistry in the stratosphere. Although being rapidly photolysed at low solar zenith angles (SZAs) it plays an important role as an indicator of the chlorine activation in polar regions during polar winter and spring at twilight conditions because of the nearly linear relation of its formation to chlorine oxide (ClO).

Here we present a new DOAS retrieval algorithm of the slant column densities (SCDs) of chlorine dioxide (OClO) and correlate this TROPOMI OClO signal with meteorological data for both Antarctic and Arctic regions.

How to cite: Pukite, J., Borger, C., Dörner, S., and Wagner, T.: OClO as observed by TROPOMI on Sentinel 5P, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-11831, https://doi.org/10.5194/egusphere-egu2020-11831, 2020.

The Sentinel-5-precursor (S5p) satellite with the TROPOMI payload was launched on 13 October 2017. It is part of the European Copernicus program and provides a set of operational products of atmospheric constituents related to air quality and climate change with almost daily global coverage. The good signal to noise ratio of the instrument enables precise measurements despite the fine spatial resolution of 3.5 x 5.5 km2. 

The ESA S5p+ Innovation activity aims at extending the list of S5p products with scientific products, which are not yet part of the operational processor, to exploit the potential of the Sentinel-5p mission’s capabilities beyond its primary objectives. The retrieval of chlorine dioxide (OClO) from S5p is among the seven funded sub projects. Chlorine dioxide is an indicator for chlorine activation in the stratosphere and thus of importance for the understanding of stratospheric ozone chemistry, in particular in the polar vortex. Chlorine dioxide was retrieved from heritage instruments (GOME, SCIAMACHY, GOME2, OMI) and the S5p OClO product will act as a continuation of these time-series.

Here we present the current status of the IUP-Bremen S5p OClO product developed within the ESA S5p+ Innovation framework. The new S5p product will be put into context with products from previous and current (e.g. GOME-2c) satellite missions as well as ground-based measurements used for validation.

How to cite: Meier, A. C., Richter, A., Pinardi, G., Van Roozendael, M., and Burrows, J. P.: Retrieval of chlorine dioxide columns from Sentinel-5p observations, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-13715, https://doi.org/10.5194/egusphere-egu2020-13715, 2020.

The column-averaged dry air mole fractions of carbon dioxide (XCO₂), methane (XCH₄) and carbon monoxide (XCO) have been measured for the first time for a whole year in Thessaloniki, Greece, using the portable Bruker EM27/SUN ground-based low-resolution Fourier Transform spectrometer, provided by the Karlsruhe Institute of Technology. The EM27/SUN is a reliable, easy-to-deploy, mobile, low-cost supplement to the Bruker IFS 125HR, a high-resolution spectrometer used in the Total Carbon Column Observing Network (TCCON). Approximately 30 of the EM27/SUN instruments constitute the Collaborative Carbon Column Observing Network (COCCON), with stations around the globe for the quantification of local sinks and sources, working as an important supplement of TCCON to increase the global density of column-averaged greenhouse gas observations

One year of measurements of XCH₄ and XCO are presented for Thessaloniki, Greece. The station is located in the center of the city. The data are compared to collocated measurements from S5P/TROPOMI using 50km and ±30 min as criteria. For the XCH₄ comparisons, the ground based XCH₄ is constantly found to be lower than the satellite product. However, for ground based retrievals of XCH₄ using the TROPOMI algorithm and IR band, the comparison with the satellite data shows a percentage difference lower than ±2%, well within product requirements. Satellite XCO is also compared to ground observations to examine if EM27/SUN concentrations are reproduced by S5P/TROPOMI and whether the temporal variations are captured

Aknowledgments

This work was co-funded by ESA within the Contract No. 4000117151/16/l-LG “Preparation and Operations of the Mission Performance Centre (MPC) for the Copernicus Sentinel-5 Precursor Satellite”. The satellite data were obtained through Sentinel-5P Expert Users Data Hub (https://s5pexp.copernicus.eu/).

This research was co-funded by the project "PANhellenic infrastructure for Atmospheric Composition and climatE change" (MIS 5021516) which is implemented under the Action "Reinforcement of the Research and Innovation Infrastructure", funded by the Operational Programme "Competitiveness, Entrepreneurship and Innovation" (NSRF 2014-2020) and co-financed by Greece and the European Union (European Regional Development Fund).

How to cite: Topaloglou, C., Mermigkas, M., Koukouli, M.-E., Balis, D., Hase, F., Landgraf, J., and Aben, I.: Comparison of one year of XCH4 and XCO measurements using a EM27/SUN low resolution FTIR spectrometer to S5P/TROPOMI methane and carbon monoxide columns at Thessaloniki, Greece, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-15056, https://doi.org/10.5194/egusphere-egu2020-15056, 2020.

Atmospheric moisture is a crucial factor for the redistribution of heat in the atmosphere, with a strong coupling between atmospheric circulation and moisture pathways which are responsible for most climate feedback mechanisms. Conventional satellite and in situ measurements provide information on water vapour content and vertical distribution; however, observations of water isotopologues make a unique contribution to a better understanding of this coupling.

In recent years, observations of water vapour isotopologue from satellites have become available from nadir thermal infrared measurements (TES, AIRS, IASI) which are sensitive to the free troposphere and from shortwave-infrared (SWIR) sensors (GOSAT, SCIAMACHY) that provide column-averaged concentrations including sensitivity to the boundary layer. The TROPOMI instrument on-board Sentinel 5P (S5p) measures SWIR radiance spectra that allow retrieval of water isotopologue columns but with much improved spatial and temporal coverage compared to other SWIR sensors promising a step-change for scientific and operational applications.

Here we present the development of the retrieval algorithm for water isotopologues from TROPOMI as part of the ESA S5p Innovation programme.  We also discuss the validation of these type of satellite products with fiducial in situ measurements and challenges when comparing with other satellite measurements. Finally, we outline the roadmap for assessing the impact of TROPOMI data against state-of-the-art isotope enabled models.

How to cite: Trent, T., Boesch, H., Somkuti, P., Schneider, M., Khosrawi, F., Diekmann, C., and Sodemann, H.: Retrieval of Stable Water Vapour Isotopologues from the TROPOMI Instrument, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-16046, https://doi.org/10.5194/egusphere-egu2020-16046, 2020.

The current scientific H₂O/HDO data product from short-wave infrared reflectance measurements by the Tropospheric Monitoring Instrument (TROPOMI) is retrieved using a profile-scaling approach with a forward model which ignores scattering. Since water is too dark in the short-wave infrared, the coverage is limited to clear-sky scenes over land. Clouds are relatively bright in this spectral region, thus retrievals over low clouds will greatly enlarge the coverage. To do so, retrievals using a forward model which accounts for scattering and fitting effective cloud parameters additionally to the trace gases are examined. Inferred effective cloud parameters are compared with measurements by the Visible Infrared Imaging Radiometer Suite (VIIRS) to optimise the cloud model. Furthermore, the impact on the validation of the retrieved H₂O/HDO columns with collocated measurements by the Total Carbon Column Observing Network (TCCON) is discussed.

How to cite: Schneider, A., Borsdorff, T., aan de Brugh, J., Lorente Delgado, A., and Landgraf, J.: Retrieving H2O/HDO above clouds using TROPOMI SWIR measurements, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-5878, https://doi.org/10.5194/egusphere-egu2020-5878, 2020.

How to cite: Borger, C., Beirle, S., Dörner, S., Sihler, H., and Wagner, T.: Total Column Water Vapour Retrieval from S-5P/TROPOMI in the Visible Blue Spectral Range, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-3408, https://doi.org/10.5194/egusphere-egu2020-3408, 2020.

The Sentinel-5 Precursor (S5P) was launched on the 13th of October 2017, with on board the TROPOspheric Monitoring Instrument (TROPOMI). The formaldehyde (HCHO) L2 product is operational since the end of 2018. The prototype of the tropospheric HCHO retrieval algorithm is developed at BIRA-IASB and implemented at the German Aerospace Center (DLR) in the S5P operational processor (De Smedt et al., 2018).

In this work, we investigate the quality of the HCHO tropospheric column product and its validation within the MPC framework (Mission Performance Center) and the S5PVT NIDFORVAL project (S5P NItrogen Dioxide and FORmaldehyde VALidation). Within NIDFORVAL, the S5P HCHO product has been validated using the full FTIR and MAXDOAS dataset. Validation results have been assessed against reported product uncertainties taking into account the full comparison error budget, showing that the product quality reaches its requirements.

Here, we focus on satellite-satellite comparison based on the OMI QA4ECV HCHO product and on ground-based validation using MAX-DOAS and Pandora network observations. About 15 HCHO measuring stations are involved, providing data corresponding to a wide range of observation conditions at mid and low latitudes, and covering remote, sub-urban, and urban polluted sites. Comparison results show usually negative biases for large HCHO columns, while a positive offset is observed for the lowest columns. For the MAX-DOAS stations providing vertical profile retrievals, the impact of a priori profiles on the comparison is assessed. The dataset allows to discuss validation results as a function of emission source. Seasonal and diurnal variations are compared. Long term variation are also monitored using the OMI and MAX-DOAS QA4ECV dataset.

How to cite: De Smedt, I., Pinardi, G., Vigouroux, C., Compernolle, S., Eichman, K. U., Langerock, B., Lerot, C., Theys, N., Vlietinck, J., Yu, H., Romahn, F., Hedelt, P., Cheng, Z., Lambert, J.-C., Loyola, D., and Van Roozendael, M. and the NIDFORVAL HCHO team: Validation of the S5P Formaldehyde L2 product using MAX-DOAS network observations, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-18189, https://doi.org/10.5194/egusphere-egu2020-18189, 2020.

The Sentinel-4 (S4) mission, the first imaging spectrometer instrument to be flown on Meteosat Third Generation Sounding (MTG-S) satellite in geostationary orbit, will provide accurate data on an hourly basis of trace gases and aerosols over Europe and Northern Africa for climate, air quality, ozone and surface UV applications. It features bands in the ultraviolet (305-400 nm), and visible (400-500 nm) with a spectral resolution of 0.5 nm and in the near-infrared (750-775 nm) ranges with a spectral resolution of 0.12 nm.

To provide simulated S4-UVN instrument data, we are working to prepare the Instrument Data Simulator (IDS). IDS is supposed to provide test data for the L1b Processor and provide capability for instrument performance and calibration monitoring. The IDS consists of two main blocks: the Scene Generator (SG) simulates the radiance/irradiance at the entrance of the instrument and the Instrument Simulator (IS) simulates the response of the instrument on the input signal. The S4-UVN IS follows as much as possible the instrument forward model and will be developed using a ’travelling spectrum’ approach. In this approach, the flux in the instrument or signal and noise is modified step-by-step by a series of algorithms representing the effects of the different components of the instrument on signal when flowing through the instrument. The IDS architecture, instrument forward model and the preliminary output of IDS will be introduced.

How to cite: Hao, N. and Gimeno Garcia, S.: Sentinel-4 Instrument Data Simulator, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-20489, https://doi.org/10.5194/egusphere-egu2020-20489, 2020.

Ground-based column measurements of trace gases by FTIR spectrometers within the Total Carbon Column Observing Network (TCCON) provide accurate ground reference for the validation of the nadir-viewing hyperspectral Tropospheric Monitoring Instrument (TROPOMI) on-board the ESA satellite Sentinel 5 Precursor (S-5P). In such intercomparisons of two independent remote soundings, errors can occur as the a priori profiles used in the respective retrievals are i) differing from each other, and ii) both different from the true atmospheric state at the moment of observation. In certain conditions of atmospheric dynamics, e.g. polar vortex subsidence or stratospheric intrusions, which strongly alter the shape of vertical concentration profiles, these intercomparison errors can become considerable (Ostler et al., 2014).

In our work funded by the German Space Agency DLR and performed as part of the ESA AO project TCCON4S5P, we search for potential sources of realistic common a priori profiles for S-5P and TCCON CH₄ and CO measurements which reduce these large errors. We examine the performance of a number of chemical transport models and data assimilation systems in reproducing dynamical effects and in minimizing intercomparison errors. In-situ profiles measured by AirCores are used as validation where they are available. We present the status and results of our ongoing work.

Reference:

Ostler, A., Sussmann, R., Rettinger, M., Deutscher, N. M., Dohe, S., Hase, F., Jones, N., Palm, M., and Sinnhuber, B.-M.: Multistation intercomparison of column-averaged methane from NDACC and TCCON: impact of dynamical variability, Atmos. Meas. Tech., 7, 4081–4101, doi:10.5194/amt-7-4081-2014, 2014. Ostler, A., Sussmann, R., Rettinger, M., Deutscher, N. M., Dohe, S., Hase, F., Jones, N., Palm, M., and Sinnhuber, B.-M.: Multistation intercomparison of column-averaged methane from NDACC and TCCON: impact of dynamical variability, Atmos. Meas. Tech., 7, 4081–4101, doi:10.5194/amt-7-4081-2014, 2014.

How to cite: Lutzmann, J., Sussmann, R., Chen, H., Hase, F., Kivi, R., Strong, K., Tsurata, A., and Warneke, T.: Independent a priori information for reduced intercomparison errors between TROPOMI and TCCON retrievals of methane and carbon monoxide, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-19764, https://doi.org/10.5194/egusphere-egu2020-19764, 2020.

The aerosol index (AER_AI) as calculated using data from the Tropospheric Monitoring Instrument (TROPOMI) onboard the ESA Sentinel 5 Precursor (S5P) platform was publically released in July 2018. The operational AER_AI dataset is available from May 2018 through the present. It is a useful data product not only for tracking ultraviolet (UV) absorbing aerosol plumes of desert dust, volcanic ash, and smoke from biomass burning but also for monitoring the quality of the TROPOMI Level 1b (L1b) data since the AER_AI calculation is very sensitive to the absolute calibration of irradiance and radiance. The aim of this work is first to highlight the new level of detail seen in aerosol plume events based on the recent switch to a reduced pixel size of 3.5 x 5.5 km. Such high spatial resolution also presents specific challenges as non-Lambertian cloud features and 3-D effects of clouds are now visible in the TROPOMI AER_AI data. Plans for an approach to flag and correct these features in future AER_AI updates will be given. Secondly this work will include an overview of the impacts on AER_AI due to observed degradation in the TROPOMI measured irradiance and wavelength-dependent features in the radiance. As a result of these L1b effects, there is a steadily increasing negative bias in the global mean AER_AI value. Examples are given how the new version of the L1b data (2.0.0) will be used to correct for this degradation-driven bias. Recommendations are also given to guide data users looking to perform trend analysis or those using AER_AI as a filter for aerosol removal or detection in other L2 data products.  

How to cite: Stein Zweers, D., Sneep, M., Kooreman, M., Stammes, P., Tilstra, G., Loots, E., and Wagner, T.: TROPOMI Aerosol Index: detailed aerosol plume tracking and plans for future development, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-20883, https://doi.org/10.5194/egusphere-egu2020-20883, 2020.

The scientific and industrial communities are handling continuously increasing amounts of data from Earth Observation (EO) satellite missions and related instruments. This is in particular the case for the atmospheric sciences communities, with the recently launched Copernicus Sentinel-5 Precursor, the upcoming Sentinel-4, -5, and ESA’s Earth Explorers scientific satellites ADM-Aeolus and EarthCARE, but also heritage missions such as ENVISAT, MetOp and OMI Aura. However, the challenge is not only to manage the large volume of data generated by each mission / sensor, but also to manage the data variety. Tools are needed to be able to rapidly and trustfully identify, from all available datasets of a specific region for a specific timeframe, all available products for a selected field (e.g. ozone, trace gases) and prepare these data into a format that is ready to be extracted and used /analyzed (Analysis-Ready Data, ARD). Exploiting potential synergies to maximise the use of data from various sources will be key to harness the full potential of the available information. In summary, there is a need of an “intelligent” packaging of subsets of the available data tailored to the users’ needs.

The scope of the “Atmospheric Mission Data Packaging” (AMiDA) project is to design, implement, and demonstrate the functionalities of an infrastructure for access and distribution of a wide variety of EO data in the field of atmospheric sciences: heritage, current, and future missions will be managed by the platform, to allow the users accessing, visualizing, and downloading a meaningful subset of this growing data stream.

AMiDA (https://amida.adamplatform.eu/en/) makes use of the baseline functionalities provided by the TOP platform (http://top-platform.eu/) that already allows accessing and manipulating a large variety of satellite, model, and non-satellite remotely sensed data. TOP is empowered with spatial and temporal homogenization and packaging capabilities to create, from heterogeneous data sources (e.g., SO₂ total column data from different satellites and numerical models) a single data structure (local data cube) for simultaneous exploitation of various data sources. The data cube can be exploited through the TOP tools (web application, Jupyter notebook and APIs) and downloaded by the user.

A comprehensive demonstration campaign will be performed through five main use cases to demonstrate the capability of AMiDA.

AMiDA is currently in its final development phase, thus the scope of the contribution is to present the initiative, preliminary results, and stimulate the discussion with potential users, analyzing their needs and see if and how they can use AMiDA to facilitate their everyday professional life.

How to cite: Natali, S., Rendl, C., Santillan, D., Hirtl, M., Scherllin-Pirscher, B., Hangler, A., Cede, A., Kreuter, A., and Retscher, C.: Atmospheric Mission Data Packaging (AMiDA), EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-21731, https://doi.org/10.5194/egusphere-egu2020-21731, 2020.

The Sentinel 5 Precursor products, call for an accurate validation. Europe can be nowadays regarded as a leader in ground-based vertical profiling observations. ACTRIS (Aerosols, Clouds, and Trace gases Research InfraStructure Network) is an EC funded infrastructure integrating European ground-based stations equipped with advanced atmospheric equipment. Among these, EARLINET (European Aerosol Research Lidar NETwork) and Cloudnet are well-established networks providing vertical profiles of aerosol and clouds with high vertical and temporal resolution. A network of ground-based stations has the ability to provide the spatio-temporal development of aerosol and cloud fields and offers a unique opportunity for the validation of observations from space. In this project, state-of-the-art instrumentations for observing aerosol and clouds will be used for validation purposes: multi-wavelength lidar (EARLINET) and Doppler cloud radar (Cloudnet).

Characterization of aerosol and cloud fields over the stations is provided by the use of EARLINET and Cloudnet data. Additional information is provided by AERONET data where available. Differences will be reported as a function of aerosol load, aerosol and cloud height, aerosol type, cloud type and underneath surface.

First results of validation efforts performed within ACTRIS in terms of a quantitative evaluation of the accuracy of S5P aerosol and cloud products will be reported. This activity is done under the EC-ACTS: Earlinet and Cloudnet - Aerosol and Clouds Teams for Sentinel-5P Validation unfunded project, which comprises 3 EARLINET/Cloudnet stations [Potenza (IT), Leipzig (DE) and Cabauw (NL)]; 3 EARLINET stations [Granada (ES), Athens (GR) and Bucharest (RO)] and 2 Cloudnet sites [Mace Head (IE) and Sodankylä (FI)].

In particular, the first results will be about the S5P Aerosol Layer Height (mandatory product) and Aerosol Optical Depth (optional product) and whenever available the AAI-based columnar Aerosol Type product.

How to cite: Mona, L., Papagiannopoulus, N., Pappalardo, G., Wandinger, U., D'Amico, G., Amiridis, V., Arboledas, L.-A., Nicolae, D., Apituley, A., O'Connor, E., and Pressler, J.: ACTRIS efforts for Sentinel 5 Precursor validation, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-21815, https://doi.org/10.5194/egusphere-egu2020-21815, 2020.

The ongoing rise in missions to observe Earth from space, especially the various Copernicus’ Sentinel systems not only increases the volume of data daily, but also contributes to the variety of data, the velocity of data availability, and its veracity. In this scenario, Sentinel 5P has already changed the way in which chemical atmospheric components are monitored daily, providing data with global coverage and a very detailed spatial resolution.

The discipline of atmospheric sciences poses an additional difficulty in efficiently accessing and analysing all available data: the variety is high as the source of atmospheric data is threefold with data coming from EO systems, models as well as in-situ measurements. The heterogeneity and multidimensionality of the so-called data triangle (EO, model, and in-situ data) make an efficient exploitation of the full potential of the available information even more challenging.

Following the successful experience of the Technology and Atmospheric Mission Platform (TAMP), TOP (http://top-platform.eu/ ) implements the concept of operational Virtual Research Environment (VRE), allowing data users to access, visualize, process, and download heterogeneous, multidimensional data.

Based on the ADAM datacube technology (https://adamplatform.eu), TOP allows exploiting the following datasets: Sentinel 5P Level 2 products (NO₂ and O₃ tropospheric columns, SO₂, CO, and CH₄ total columns, and aerosol index); Copernicus Atmosphere Monitoring Service (CAMS) global (surface PM₁₀, total column NO₂, SO₂, and O₃) and regional (surface PM₁₀, NO₂, SO₂ and O₃) analysis and forecast fields; European Environmental Agency (EEA) measurements (CO, NO₂, PM₁₀, SO₂).

Users can visualize and process all available data through a web application user interface (Data Analysis and Visualization Environment – DAVE), through a Jupyter notebook interface, and using the ADAM APIs and libraries to directly access available data.

TOP is deployed on the Mundi DIAS infrastructure (https://mundiwebservices.com/). This allows accessing always most recent satellite products (reprocessed, offline, near real time), model output (analyses and forecasts – up to 5 days) and station measurements (full archive, updated daily).

TOP is the first operational platform with the data triangle implemented. By creating an atmospheric multi-source data cube, it stimulates a multi-disciplinary scientific approach and significantly facilitates scientific professional life.

How to cite: Natali, S., Rendl, C., Triebnig, G., Santillan, D., Hirtl, M., and Scherllin-Pirscher, B.: Technology and atmospheric mission platform - OPerations (TOP), EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-19392, https://doi.org/10.5194/egusphere-egu2020-19392, 2020.

How to cite: Douros, J., Eskes, H., and Veefkind, P.: Comparisons between Sentinel-5P TROPOMI NO2 and the European ensemble air quality forecasts of CAMS, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-8514, https://doi.org/10.5194/egusphere-egu2020-8514, 2020.

We present our new and improved version (version 4.0) of the NASA standard nitrogen dioxide (NO2) product from the Ozone Monitoring Instrument (OMI) on the Aura satellite. This version incorporates the most important improvements proposed for regional OMI NO₂ products by expert users, and enhances NO2 data quality on a global scale through improvements in the Air Mass Factors (AMFs) in several ways. The algorithm is based on a conceptually new, geometry-dependent Lambertian surface equivalent reflectivity (GLER) operational product. GLER is calculated using the vector radiative transfer model VLIDORT, which uses as input high–resolution bidirectional reflectance distribution function (BRDF) information from NASA’s Aqua MODIS instrument over land and the wind-dependent Cox–Munk wave-facet slope distribution over water, the latter with a contribution from the water-leaving radiance. The GLER and our corresponding, consistently retrieved effective cloud fraction and O₂-O₂ optical centroid cloud pressures provide inputs to the new NO₂ AMF algorithm, which increases tropospheric NO₂ by up to 50% in highly polluted areas; the differences include both cloud and surface BRDF effects as well as biases between the MODIS and OMI-based surface reflectance data sets. We assess the new product using independent observations from ground-based and airborne instruments. The improved NO₂ data record could be beneficial for studies related to emissions and trends of nitrogen oxides (NO_x) and co-emitted gases.

How to cite: Lamsal, L., Krotkov, N., Vasilkov, A., Marchenko, S., Joiner, J., Qin, W., Yang, E.-S., Swartz, W., Choi, S., Fasnacht, Z., Haffner, D., and Fisher, B.: New-generation OMI NO2 Standard Product: Algorithm description and initial results, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-10230, https://doi.org/10.5194/egusphere-egu2020-10230, 2020.

Copernicus Sentinel-5 Precursor (S-5P) is the first of a series of atmospheric chemistry missions within the European Commission’s Copernicus Programme, launched successfully in October 2017 and since end April 2018 in its operational phase. S-5P provides continuity in the availability of global atmospheric data products between its predecessor missions SCIAMACHY (Envisat) and OMI (AURA) and the future Sentinel-4 and -5 series. S-5P delivers unique data regarding the sources and sinks of trace gases with a focus on the lower Troposphere including the planet boundary layer due to its enhanced spatial, temporal and spectral sampling capabilities as compared to its predecessors.

The S-5P satellite carries a single payload, namely TROPOMI (TROPOspheric Monitoring Instrument) that was jointly developed by The Netherlands and ESA. Covering spectral channels in the UV, visible, near- and short-wave infrared, it measures various key species including tropospheric/stratospheric ozone, NO2, SO2, CO, CH4, CH2O as well as cloud and aerosol parameters.

The geophysical validation and characterization of the TROPOMI data products during the phase E2 is conducted by ESA at different levels. The so-called Mission Performance Center carries out the routine validation throughout the mission life-time and rely on the availability of independent data sets for example from ground-based measurements or the so-called Fiducial Reference Measurement data sets, as well as the contributions from independent national Validation Teams coordinated by ESA under the Sentinel 5 Precursor Validation Team (S5PVT).

The current status of the ESA S-5P routine Validation activities will be discussed in this paper.

How to cite: Dehn, A., Zehner, C., Saavedra De Miguel, L., Lambert, J.-C., Veefkind, P., and Loyola, D.: Copernicus Sentinel-5 Precursor Routine Validation, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-16568, https://doi.org/10.5194/egusphere-egu2020-16568, 2020.

Sentinel-5 Precursor (S-5P), launched in October 2017, is the first mission of the Copernicus Programme dedicated to the monitoring of air quality and climate. Its characteristics, such as the fine spatial resolution, introduce many new opportunities and challenges, requiring to carefully assess the quality and validity of the generated data products by comparison with independent reference observations.

In the presented study, the S-5P/TROPOMI tropospheric nitrogen dioxide (NO₂) L2 product (3.5 x 7 km² at nadir observations) has been validated over strongly polluted urban regions based on comparison with coincident high-resolution airborne remote sensing observations (~100 m²). Airborne imagers are able to map the horizontal distribution of tropospheric NO₂, as well as its strong spatio-temporal variability, at high resolution and with high accuracy. Satellite products can be optimally assessed based on airborne observations as a large amount of satellite pixels can be fully mapped in a relatively short time interval, reducing the impact of spatiotemporal mismatches. Additionally, such data sets allow to study the TROPOMI subpixel variability and impact of signal smoothing due to its finite satellite pixel size, typically coarser than fine-scale gradients in the urban NO₂ field.

In the framework of the S5PVAL-BE campaign, the Airborne Prism EXperiment (APEX) imaging spectrometer has been deployed during four mapping flights (26-29 June 2019) over the two largest urban regions in Belgium, i.e. Brussels and Antwerp, in order to map the horizontal distribution of tropospheric NO₂. Per flight, 15 to 20 TROPOMI pixels were fully covered by approximately 5000 APEX measurements for each TROPOMI pixel. Mapping flights and ancillary ground-based measurements (car-mobile DOAS, MAX-DOAS, CIMEL, ceilometer, etc.) were conducted in coincidence with the overpass of TROPOMI (typically between noon and 2 PM UTC). The TROPOMI and APEX NO₂ vertical column density (VCD) retrieval schemes are similar in concept. Retrieved NO₂ VCDs were georeferenced, gridded and intercompared. As strongly polluted areas typically exhibit strong NO₂ vertical gradients (besides the strong horizontal gradients), a custom TROPOMI tropospheric NO₂ product was computed and compared as well with APEX by replacing the coarse 1° x 1° a priori NO₂ vertical profiles from TM5-MP by NO₂ profile shapes from the CAMS regional CTM ensemble at 0.1° x 0.1°.

Overall for the ensemble of the four flights, the standard TROPOMI NO₂ VCD product is well correlated (R= 0.94) but biased low (slope = 0.73) with respect to APEX NO₂ retrievals. When replacing the TM5-MP a priori NO₂ profiles by CAMS-based profiles, the slope increases to 0.88. When calculating the NO₂ VCD differences, the bias is on average -1.3 ± 1.2 x 10¹⁵ molec cm^-2 or -16% ± 11% for the difference between APEX NO₂ VCDs and the standard TROPOMI NO₂ VCD product. The bias is substantially reduced when replacing the coarse TM5-MP a priori NO₂ profiles by CAMS-based profiles, being -0.1 ± 1.1  x 10¹⁵ molec cm^-2 or -0.1% ± 11%. Both sets of retrievals are well within the accuracy requirement of a maximum bias of 25-50% for the TROPOMI tropospheric NO₂ product for all individual compared pixels.

How to cite: Tack, F., Merlaud, A., Iordache, M.-D., Pinardi, G., Dimitropoulou, E., Eskes, H., Bomans, B., and Van Roozendael, M.: Assessment of the S-5P tropospheric NO2 product based on coincident airborne APEX observations over polluted regions, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-19261, https://doi.org/10.5194/egusphere-egu2020-19261, 2020.

For more than two years now the first atmospheric satellite of the Copernicus EO programme, Sentinel-5p (S5P) TROPOMI, has acquired spectral measurements of the Earth radiance in the visible range, from which near-real-time (NRTI) and offline (OFFL) processors retrieve operationally the total, tropospheric and stratospheric  column abundance of atmospheric NO₂.  In support of these routine operations, the S5P Mission Performance Centre (MPC) performs continuous QA/QC of these data products and produces key Quality Indicators enabling users to verify the fitness-for-purpose of the S5P data. Quality Indicators are derived from comparisons to ground-based reference data, both station-by-station in monitoring mode in the S5P Automated Validation Server (AVS) and globally in more complex in-depth analyses.  Complementary quality information is obtained from product intercomparisons (NRTI vs. OFFL) and from satellite-to-satellite comparisons.  After two years of successful operation we present here a consolidated overview of the quality of the S5P TROPOMI NO₂ data products delivered publicly.

S5P NO2 data are compared routinely to ground-based network measurements collected through either the ESA Validation Data Centre (EVDC) or network data archives (NDACC, PGN). Direct-sun measurements from the Pandonia Global Network (PGN) serve as a reference for total NO₂ validation, Multi-Axis DOAS network data for tropospheric  NO₂ validation, and NDACC zenith-scattered-light DOAS network data for stratospheric NO₂ validation.  Comparison methods are optimized to limit spatial and temporal mismatch to a minimum (information-based spatial co-location strategy, photochemical adjustment to account for local time measurement difference). Comparison results are analyzed to derive Quality Indicators and to conclude on the compliance w.r.t. the mission requirements. This include estimates of: (1) the bias, as proxy for systematic errors, (2) the dispersion of the differences, which combines random errors with seasonal and irreducible mismatch errors, and (3) the dependence of bias and dispersion on key influence quantities (surface albedo, cloud cover…)

Intercomparison of S5P products (NRTI vs. OFFL) and comparison to other satellite data, including a similar processing of OMI measurements, complement the ground-based validation with relative biases and spatio-temporal patterns/artefacts related to instrumental issues (e.g. striping) and to the sensitivity to geophysical features (e.g. clouds and sea/ice albedo contrast).  

Overall, the MPC quality assessment of S5P NO₂ data concludes to an excellent performance for the stratospheric column data (bias2 vs. ground-based data. This dispersion larger than the mission requirement on data precision can partly be attributed to comparisons errors such as those due to differences in horizontal resolution. Total column data are found to be biased low by 20%, with a 30% station-to-station scatter. After gridding to monthly means on a 0.8°x0.4° grid, comparisons to OMI data yield a much smaller dispersion (within the requirement of 0.7Pmolec/cm²), and a minor relative bias. NRTI and OFFL perform similarly, even if they occasionally differ in specific cases of direct comparisons.       

How to cite: Verhoelst, T., Compernolle, S., Granville, J., Keppens, A., Pinardi, G., Lambert, J.-C., Eichmann, K.-U., Eskes, H., Niemeijer, S., Fjæraa, A. M., Pazmoni, A., Goutail, F., Pommereau, J.-P., Cede, A., and Tiefengraber, M.: Quality assessment of two years of Sentinel-5p TROPOMI NO2 data , EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-15036, https://doi.org/10.5194/egusphere-egu2020-15036, 2020.

The Tropospheric Monitoring Instrument (TROPOMI) with a higher spatial resolution is a push broom UVIS spectrometer carried on the S5P satellite which was launched on October 13th, 2017.  But compared to the widely used OMI and GOME-2, TROPOMI NO2 products have not been extensively used in China. To evaluate the TROPOMI NO2 products, we present a comparison between TROPOMI NO2 products and MAX-DOAS observations in Xuzhou, eastern China from April 2018 to September 2019. We find a high correlation, but a clear underestimation. We find that solar zenith angle, viewing zenith angle, the cloud fraction and wind speed will affect the evaluation results. We examine the retrievals of TROPOMI tropospheric NO2 over China, contrasting them with the retrievals of OMI. We find that TROPOMI has better ability to resolve smallscale plumes and distinguish the distribution of NO2 concentration on a city scale. Our goal is to support the application of TROPOMI for NO2 observations and deriving emissions from urban or industrial facilities over China.

How to cite: Qin, K., He, Q., and Shi, J.: Evaluation of TROPOMI Tropospheric NO2 VCDs over China, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-1895, https://doi.org/10.5194/egusphere-egu2020-1895, 2020.

Operational retrievals of tropospheric trace gases from space-borne spectrometers are made using 1D radiative transfer models. To minimize cloud effects generally only partially cloudy pixels are analysed using simplified cloud contamination treatments based on radiometric cloud fraction estimates and photon path length corrections based on oxygen collision pair (O₂-O₂) or O₂A-absorption band measurements. In reality, however, the impact of clouds can be much more complex, involving scattering of clouds in neighbouring pixels and cloud shadow effects. Therefore, to go one step further, other correction methods may be envisaged that use sub-pixel cloud information from co-located imagers. Such methods require an understanding of the impact of clouds on the real 3D radiative transfer. We quantify this impact using the MYSTIC 3D radiative transfer model. The generation of realistic 3D input cloud fields, needed by MYSTIC (or any other 3D radiative transfer model), is non-trivial. We use cloud data generated by the ICOsahedral Non-hydrostatic (ICON) atmosphere model for a region including Germany, the Netherlands and parts of other surrounding countries. The model simulates realistic liquid and ice clouds with a horizontal spatial resolution of 156 m and it has been validated against ground-based and satellite-based observational data.

As a trace gas example, we study NO₂, a key tropospheric trace gas measured by the atmospheric Sentinels. The MYSTIC 3D model simulates visible spectra, which are ingested in standard DOAS retrieval algorithms to retrieve the NO₂ column amount. Spectra are simulated for a number of realistic cloud scenarios, snow free surface albedos, and solar and satellite geometries typical of low-earth and geostationary orbits. The retrieved NO₂ vertical column densities (VCD) are compared with the true values to identify conditions where 3D cloud effects lead to significant biases on the NO₂ VCDs. A variety of possible mitigation strategies for such pixels are then explored.

How to cite: Yu, H., Kylling, A., Emde, C., Mayer, B., Stebel, K., Van Roozendael, M., and Veihelmann, B.: Impact of 3D cloud structures on tropospheric NO2 column measurements from UV-VIS sounders, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-17626, https://doi.org/10.5194/egusphere-egu2020-17626, 2020.

Remote sounding of atmospheric composition makes use of satellite measurements with very heterogeneous characteristics. In particular, the determination of vertical profiles of gases in the atmosphere can be performed using measurements acquired in different spectral bands and with different observation geometries. The most rigorous way to combine heterogeneous measurements of the same quantity in a single Level 2 (L2) product is simultaneous retrieval. The main drawback of simultaneous retrieval is its complexity, due to the necessity to embed the forward models of different instruments into the same retrieval application. To overcome this shortcoming, we developed a data fusion method, referred to as Complete Data Fusion (CDF), to provide an efficient and adaptable alternative to simultaneous retrieval. In general, the CDF input is any number of profiles retrieved with the optimal estimation technique, characterized by their a priori information, covariance matrix (CM), and averaging kernel (AK) matrix. The output of the CDF is a single product also characterized by an a priori, a CM and an AK matrix, which collect all the available information content. To account for the geo-temporal differences and different vertical grids of the fusing profiles, a coincidence and an interpolation error have to be included in the error budget.
In the first part of the work, the CDF method is applied to ozone profiles simulated in the thermal infrared and ultraviolet bands, according to the specifications of the Sentinel 4 (geostationary) and Sentinel 5 (low Earth orbit) missions of the Copernicus program. The simulated data have been produced in the context of the Advanced Ultraviolet Radiation and Ozone Retrieval for Applications (AURORA) project funded by the European Commission in the framework of the Horizon 2020 program. The use of synthetic data and the assumption of negligible systematic error in the simulated measurements allow studying the behavior of the CDF in ideal conditions. The use of synthetic data allows evaluating the performance of the algorithm also in terms of differences between the products of interest and the reference truth, represented by the atmospheric scenario used in the procedure to simulate the L2 products. This analysis aims at demonstrating the potential benefits of the CDF for the synergy of products measured by different platforms in a close future realistic scenario, when the Sentinel 4, 5/5p ozone profiles will be available.
In the second part of this work, the CDF is applied to a set of real measurements of ozone acquired by GOME-2 onboard the MetOp-B platform. The quality of the CDF products, obtained for the first time from operational products, is compared with that of the original GOME-2 products. This aims to demonstrate the concrete applicability of the CDF to real data and its possible use to generate Level-3 (or higher) gridded products.
The results discussed in this presentation offer a first consolidated picture of the actual and potential value of an innovative technique for post-retrieval processing and generation of Level-3 (or higher) products from the atmospheric Sentinel data.

How to cite: Zoppetti, N., Ceccherini, S., Barbara, F., Del Bianco, S., Gai, M., Poli, G., Tirelli, C., and Cortesi, U.: The Complete Data Fusion as a ready to use tool for the exploitation of atmospheric Sentinel ozone profiles, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-19372, https://doi.org/10.5194/egusphere-egu2020-19372, 2020.

The eruption of the Raikoke volcano (Kuril Islands) on June 21-22, 2019, created a large plume of sulfur dioxide (SO₂) that reached the upper troposphere and lower stratosphere. The plume persisted in the atmosphere over the middle and high latitudes of the Western Hemisphere for more than a month creating a rare validation opportunity with multiple collocated measurements from ground and space both revealing enhanced SO₂ vertical column densities (VCDs). Moreover, since the plume was often located over high latitudes, multiple orbits per day from the polar orbiting satellites could be utilized. Pandora sunphotometer measurements at Edmonton and Eureka, Canada, and at Fairbanks, Alaska, and Brewer spectrophotometer measurements at seven Canadian sites (Saturna, Edmonton, Churchill, Resolute, Eureka, and Alert) reported SO₂ values up to 15 Dobson Units (DU, where 1 DU = 2.69 × 10¹⁶ molecules/cm²). These measurements were compared with satellite SO₂ VCDs obtained by the Sentinel 5p TROPOspheric Monitoring Instrument (TROPOMI), AURA Ozone Monitoring Instrument (OMI), and Suomi NPP Ozone Mapping Profiling Suite (OMPS). Back-trajectory Lagrangian model analysis and satellite SO₂ profile measurements by the Atmospheric Chemistry Experiment mission Fourier transform spectrometer (ACE/FTS) on board the Canadian satellite SCISAT demonstrated that the volcanic plume was located at 8-25 km. In general, ground-based and satellite measurements show a very good agreement. However, the exact ground-based and satellite viewing geometry should be considered when such measurements are taken near the edge of the plume.

How to cite: Fioletov, V., Sioris, C., Zhao, X., Griffin, D., McLinden, C., Brohart, M., Lee, S. C., Carn, S., Bognar, K., Strong, K., Mao, J., Theys, N., Loyola, D., Hedelt, P., Krotkov, N., Li, C., and Boone, C.: Ground-based and satellite measurements of the SO2 plume from the eruption of Raikoke volcano in June 2019, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-11221, https://doi.org/10.5194/egusphere-egu2020-11221, 2020.

The European Union’s Copernicus Atmosphere Monitoring Service (CAMS) operationally provides daily forecasts of global atmospheric composition. It uses the ECMWF Integrated Forecasting System (IFS), which includes meteorological and atmospheric composition variables, such as reactive gases, greenhouse gases and aerosols, for its global forecasts and reanalyses. The current green-house gases operational suite monitors CH4 and CO2 and assimilates TANSO and IASI retrievals for both species. The TROPOspheric Monitoring Instrument (TROPOMI) on board the Sentinel-5 Precursor (S5P) satellite launched in October 2017 yields a wealth of atmospheric composition data, including CH₄ retrievals at unprecedented high horizontal resolution (7km) and up to daily revisit time. We used the IFS to perform monitoring experiments at different horizontal resolutions (25 km and 9 km). We also performed first data assimilation experiments at 25 km horizontal resolution.

This first set of monitoring experiments shows the potential of the TROPOMI CH₄ retrievals to correct known biases that exist in the current CAMS analyses and forecasts. Assimilation experiments of TROPOMI CH₄ shows that adding the instrument in the operational chain would significantly improve the analysis and forecasts. Detection of CH₄ sources seen by TROPOMI compared to CAMS also shows the potential of the instrument to inform on and infer anthropogenic and natural sources. For example, discrepancies between TROPOMI retrievals and CAMS fields in the CH₄ levels associated with oil and gas extraction activities show very promising perspectives for monitoring and analysis of CH₄ concentration and emissions. We will finally discuss the challenges and progress made towards performing inversions using the IFS operational system.  

How to cite: Barre, J., Aben, I., Ades, M., Agusti-Panareda, A., Balsamo, G., Bousserez, N., Choulga, M., Engelen, R., Flemming, J., Inness, A., Kipling, Z., Landgraf, J., Lorente-Delgado, A., Massart, S., McNorton, J., Parrington, M., and Peuch, V.-H.: Atmospheric methane monitoring and analysis using tropOMI retrievals at ECMWF., EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-10480, https://doi.org/10.5194/egusphere-egu2020-10480, 2020.