While shipping is generally the most energy-efficient freight transportation mode (in terms of gCO2 t^-1 km^-1), its intensive use (80 % to 90 % of global merchandise trade volume), coupled with high pollutant emission factors, leads to serious impact on the environment and the human health. The primary pollutants emitted by ships, nitrogen oxides (NO_x = NO₂ + NO), sulphur oxides (SO_x, mainly SO₂) and particulate matter (PM), degrade the air quality and are involved in the formation of secondary pollutants as tropospheric ozone (O₃). As 70 % of ship emissions occur within 400 km of coastlines, ship emissions have strong impact in harbour cities and coastal areas situated along high traffic shipping lanes.

Compliance monitoring for fuel sulphur content (FSC) is usually done by the collection and the analysis of fuel samples by competent authorities from ships at berth. The complexity of the method results in very few ships being formally controlled. In consequence, various remote compliance monitoring techniques of FSC have been developed in the last years, mainly involving sniffer techniques (extractive methods coupled with analyser instruments) performed from fixed or moving (e.g., manned and unmanned aircrafts, ships) platforms. Optical remote sensing techniques such as differential optical absorption spectroscopy (DOAS) have also been applied to shipping emission monitoring in the past years.

Here we present results of several ship-based campaigns conducted in the last years (in the Mediterranean Sea in 2019 and 2021, and in the English Channel in May 2022), with a focus on the DOAS technique. While the performed DOAS zenith measurements are not fully suitable to conduct a quantitative monitoring of the ship compliance to the FSC regulations, we propose a method to qualitatively identify potential non-compliant ships. Comparisons are made with state-of-the-art sniffer measurements. Despite the larger uncertainty yielded by this technique in comparison to sniffer systems, it may be applied for the guidance of formal controls (e. g., authorities at port).

During the English Channel campaign in May 2022, we modified our DOAS setup in order to sequentially scan various elevation angles from the horizon to the zenith (i.e., multi axis DOAS, MAX-DOAS) and, thus, to retrieve vertical tropospheric columns of NO₂. Here we compare our shipborne MAX-DOAS NO₂ columns to the ones retrieved from TROPOMI (TROPOspheric Monitoring Instrument). TROPOMI could be further involved in the monitoring of shipping emissions as it has been recently used to identify the emission plumes of single (or group of) ships. Therefore, its validation with independent datasets at sea is needed to strengthen the monitoring of shipping emissions.

How to cite: Prignon, M., Conde, V., Timothy J., S., Anu-Maija, S., Jasper, V. V., and Johan, M.: DOAS applied to shipping emission monitoring: compliance assessment and comparison to satellite measurements, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-2046, https://doi.org/10.5194/egusphere-egu23-2046, 2023.

GEMS (Geostationary Environmental Monitoring Spectrometer), the world’s first geostationary environmental satellite was successfully launched in February 2020 and keeps monitoring the trace gases around East Asia. For improving the GEMS retrieval algorithms and validation of the products, NIER (National Institute of Environmental Research) organized two international field campaigns in Korea: GMAP2021 (GEMS MAP of Air Pollution) and SIJAQ2022 (Satellite Integrated Joint monitoring of Air Quality), respectively in winter and summer season. In the framework of these campaigns, to fill the gap of the reference ground remote sensing observation network, additional Pandora and MAX-DOAS instruments were installed in SMA (Seoul Metropolitan Area), Ulsan, and Busan. In addition, we operated Car-DOAS and GCAS (GeoCAPE Airborne Simulator) flight measurements around the SMA and the Southeastern region to catch the detailed distribution of emission sources. Preliminary results indicate different diurnal variation patterns of NO₂ columns in SMA and the Southeastern region, visible both in ground-based and GEMS data. Car-DOAS measurements show a detailed distribution of trace gases at city level and for a few days during the summer season (SIJAQ2022), Car-DOAS even caught some well-synchronized high SO₂ and HCHO signals with NO₂, which can be related to anthropogenic emissions around the industrial area and in the case of the SMA emission estimation measurement, nice plumes were observed along the wind direction on good meteorological condition days.

How to cite: Bae, K., Song, C.-K., Richter, A., Wagner, T., Roozendael, M. V., Lange, K., Boesch, T., Ziegler, S., Merlaud, A., Park, S. S., Park, J.-U., and Hong, H.: Preliminary Results of the GMAP/SIJAQ Campaign: Remote Sensing Measurements of Air Pollution over Korea, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-4636, https://doi.org/10.5194/egusphere-egu23-4636, 2023.

  In addition to local emissions and atmospheric chemical reactions, regional transport is also an important source of atmospheric pollutants. Satellite-based remote sensing can obtain the spatial distribution of air pollutants in a large range. However, due to the influence of cloud coverage, there is the problem of data missing, which make it difficult to directly use satellite data for quantitative assessment of regional transport. In this study, we used satellite remote sensing from TROPOMI to update the emissions of WRF-Chem modeling. Then, the spatial distribution of regional transport fluxes was obtained through the updated modeling, and the output areas of air pollutants were identified in a large range of regional pollution events. We find that with the overall improvement of air quality in the Beijing-Tianjin-Hebei region, the contribution of external input to air pollution in Beijing from surrounding cities shows a downward trend, while the impact of local emissions become more prominent. Besides, the transports through elevated altitude were investigated through ground-based remote sensing. We found that the transport heights and source regions for different pollutants are quite different. Aerosols and sulfur dioxide (SO₂) are significantly affected by the long-distance transport across the upper boundary layer; nitrogen dioxide (NO₂) is mainly from local emissions and transport from surrounding area across the lower boundary layer; while the regional transport of formaldehyde (HCHO) is not obvious. Moreover, regional transport through elevated altitudes not only directly brings air pollutants, but also can cause the inversion of the vertical structure of aerosols. The inverse structure of aerosols can further induce adverse meteorological conditions through the interaction between pollution and meteorology, and then aggravate air pollution.

How to cite: Hu, Q., Zhu, Y., Zhang, C., Su, W., Ji, X., Xing, C., Liu, H., Tan, W., Li, Q., and Liu, C.: Regional transport of air pollutants from stereoscopic remote sensing observation, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-5483, https://doi.org/10.5194/egusphere-egu23-5483, 2023.

A major challenge in Differential Optical Absorption Spectroscopy (DOAS) is the characterization of the light path. For the determination of the light path length, cloud conditions are essential. While instruments like a LIDAR/ceilometer provide information on cloud base height in zenith direction, it is often quite challenging to obtain information on cloud coverage in the line of sight of a Multi-Axes-DOAS (MAX-DOAS) instrument.

In this study, we apply an existing cloud classification algorithm using combined information from the colour index and the O₄ slant column density (Wagner et al., 2013) on spectra recorded by a MAX-DOAS instrument. In order to validate the algorithm, a MAX-DOAS with camera measurements of the sky conditions carried out at the Max Planck Institute for Chemistry in Mainz for several months. The results of the cloud classification algorithm are compared to the recordings of the cameras in order to analyse the performance of the algorithm.

How to cite: Reischmann, L., Ziegler, S., Beirle, S., Kumar, V., Donner, S., and Wagner, T.: Validation of a MAX-DOAS instrument-based cloud classification algorithm, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-8101, https://doi.org/10.5194/egusphere-egu23-8101, 2023.

Multi-Axis Differential Optical Absorption Spectroscopy (MAX-DOAS) has been widely used in the three-dimensional monitoring of air pollutants. It is of great significance for MAX-DOAS to reconstruct the state of air pollutants by establishing an accurate vertical profile retrieval algorithm. At present, the profile retrieval algorithm of MAX-DOAS mainly adopts the iterative method based on a priori profile, which leads to strong dependence on priori profiles. We try to reduce the dependence on priori profiles by first calculating the vertical column density and then calculating the vertical distribution from observation. Therefore, we propose a new MAX-DOAS trace gas profile inversion algorithm - McPrA (Monte Carlo profile inversion algorithm by Anhui Institute of Optics and Fine Mechanics (AIOFM)). The algorithm uses Monte Carlo method to solve the optimal estimation problem of the gas profile. Firstly, the gas vertical column density is obtained through the air mass factor calculated by the radiative transfer model SCIATRAN. Secondly, the vertical distribution of trace gas is retrieved by combining the weight function with the a priori profile. Besides, we introduce the normalization process in the vertical distribution solution to make the prior profile better match the weight function. McPrA can set the vertical resolution of profile by modifying the grid, and we increase the vertical resolution of gas profile to 50m. By conducting sensitivity experiments on parameters such as Monte Carlo sampling, covariance matrix and the priori profiles, the optimal configuration of retrieval parameter is obtained. At the same time, the degree of freedom is more than 3.0. Finally, comparative verification experiments were carried out to compare with in situ data from LP-DOAS and National Air Quality Monitoring Station. The correlation coefficient for NO₂ VMR at the first layer retrieved by McPrA in 50 m grid reached above 0.89. The comparison of NO₂ profiles retrieval by McPrA with that from WRF-Chem and simulation of synthetic data also shows that McPrA algorithm can retrieve trace gas profiles accurately.

How to cite: Zheng, J., Xie, P., Tian, X., Xu, J., Li, A., Ren, B., Hu, F., Hu, Z., Lv, Y., and Zhang, Z.: McPrA - a new trace gas profile retrieval algorithm for MAX-DOAS, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-11128, https://doi.org/10.5194/egusphere-egu23-11128, 2023.

Ship-based trace gas measurements are of particular interest to the scientific community as they fill a gap in knowledge of trace gas concentrations in the marine boundary layer (MBL) on the open ocean. Remote sensing techniques, such as Multi AXis Differential Optical Absorption Spectroscopy (MAX-DOAS), offer the capability of probing air masses located further away from the ship, compared to in situ instruments. In this way, MAX-DOAS measurements taken during ship cruises can be used to examine larger volumes of air in the MBL where routinely measured data is sparse.

We present measurements of a MAX-DOAS system installed on the research vessel Sonne during the cruise SO287 from Las Palmas (Gran Canaria, Spain) to Guayaquil (Ecuador) from the 11th of December 2021 until the 11th of January 2022.    
Ship-based anthropogenic emissions have been identified as higher slant column densities (SCD) of nitrogen dioxide (NO₂) and sulphur dioxide (SO₂) while biogenic emissions are mainly found close to land, as indicated by higher SCDs of formaldehyde (HCHO). On the open ocean, the frequently detected abundance of iodine monoxide (IO) emphasizes that the MBL is mainly dominated by emissions from the ocean (algae) in the absence of anthropogenic emissions.               
In a second step, these SCD results have been analysed with the profiling algorithm BOREAS to further assess the vertical extent of trace gases in the MBL. Since trace gas concentrations are highest in the lowest kilometre, emission sources close to the shipping route and the ocean surface dominate the measurements taken during cruise SO287.

How to cite: Bösch, T., Latsch, M., Richter, A., Wittrock, F., and Burrows, J. P.: Measurements of trace gases with a MAX-DOAS system during a ship cruise from the Canaries to Ecuador (SO287) on board of RV Sonne, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-11376, https://doi.org/10.5194/egusphere-egu23-11376, 2023.

Remote sensing measurements of greenhouse gases from aircraft to detect and quantify greenhouse gas emissions began about 15 years ago. These measurements have been exploited to detect and quantify predominantly anthropogenic emissions. However, with new satellite systems targeting especially methane (CH₄) emissions on different scales, high-precision airborne measurements are needed to validate these satellite systems and detect and quantify emissions too small to be detected from space-based sensors.

For this, the MAMAP2D family of airborne passive imaging remote sensing instruments has been and is being built at the Institute of Environmental Physics of the University of Bremen. MAMAP2D-Light, the first of this family, is a lightweight, compact spectrometer measuring carbon dioxide (CO₂) and CH₄ enhancements in a short-wave infrared band around 1.6 µm with a spectral resolution of ~1.1 nm. It was flown successfully on a Diamond HK36 TTC-ECO motor glider aircraft of the Jade University of Applied Sciences in Wilhelmshaven and the High Altitude Long Range operations (HALO) aircraft of DLR during the COMET 2.0 Arctic campaign in Canada. The MAMAP2D instrument, the next biggest in the MAMAP2D family, covers the SWIR band with a higher spectral resolution and additionally contains a near-infrared channel covering O₂ absorption around 760 µm for path-length correction and is currently assembled in the laboratory.

In this poster, we will present the spectral characterization of the MAMAP2D-Light instrument as flown during the COMET 2.0 Arctic campaign and assess its performance for detecting local CH₄ and CO₂ gradients. Additionally, initial laboratory characterizations of the MAMAP2D breadboarding activity will be presented.

How to cite: Borchardt, J., Gerilowski, K., Huhs, O., Krautwurst, S., Bovensmann, H., Bösch, H., and Burrows, J. P.: The airborne greenhouse gas observation systems MAMAP2D-Light and MAMAP2D – Characterization and performance assessment, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-15430, https://doi.org/10.5194/egusphere-egu23-15430, 2023.

Transit cruises of German research vessels across oceans provide a unique platform for MAX-DOAS measurements of atmospheric trace gases such as nitrogen dioxide (NO₂), formaldehyde (HCHO) and sulphur dioxide (SO₂). The Deep Blue/PORD campaign took place from 24 June to 21 July 2022. During that period the research vessel SONNE was crossing the Pacific in meridional direction from 22° S to 54° N in an area that is typically used as reference for satellite data due to its large distance from anthropogenic emission sources.

In this study we focus on three trace gases: NO₂ columns provide information on the meridional distribution of stratospheric NO₂ as well as the distribution of tropospheric background NO₂ above the marine boundary layer. For the analysis, high signal “peaks” that only last a short time are filtered as they most likely originate from the ship exhaust. First results show a minimum of total NO₂ columns between the equator and about 15° N. HCHO and SO₂ mainly appear as plumes from nearby islands and/or volcanoes in the Solomon Sea, where biogenic and volcanic activities are naturally high. In combination with the onboard instrumentation (Ceilometer, Pyranometer and a cloud camera) this data set provides a detailed description of the atmosphere along the cruise track.

How to cite: Ziegler, S., Lauster, B., Beirle, S., Donner, S., and Wagner, T.: First MAX- DOAS results of the SO292-2 cruise across the Pacific in June/July 2022: Nouméa (New-Caledonia) to Dutch Harbor (Alaska, USA), EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-2310, https://doi.org/10.5194/egusphere-egu23-2310, 2023.

The AOTF-based NO₂ camera is a remote sensing instrument primarily aimed at imaging and quantifying the NO₂ field above cities or in industrial plumes. The measurement principle consists in acquiring a number of spectral images of the scene at selected wavelengths. Each pixel is therefore recording a discrete spectrum of the radiance collected in its acceptance cone, enabling the retrieval of the NO₂ column density in its optical path by application of the DOAS method on the measured spectrum.

The core element of the instrument principle is the acousto-optical tunable filter (AOTF). This device works under the principle of the acousto-optical interaction, the coupling of the light electric field with the modulation of the crystal lattice by a shear acoustic wave created by a transducer. The coupling takes place at a single wavelength, and diffracts that part of the spectrum into another direction. By blocking the undiffracted light beam, and imaging the diffracted order, one can capture a monochromatic image of the scene.

We propose to expand the capabilities of the NO₂ camera by exploiting another aspect of the acousto-optic interaction. The coupling between light and sound actually takes place in a birefringent crystal (TeO₂), and one usually works with a single linear polarization of the incoming light (e-light, or o-light). The two polarization components are diffracted in different directions. If the current design is modified such that the two components can be imaged, then an information on the degree of linear polarization of the light can be obtained.

In the atmosphere, the scattering of light by air (Rayleigh), and particles (Mie) is controlling the state of polarization of the scattered solar light. Hence, aerosols not only introduce a smooth spectral signatures, but also a change of the state of polarization. The proposed modification of the NO₂ camera design can provide some sensitivity on this, potentially enhancing the scientific return of the instrument with aerosol retrievals capabilities. The new instrumental design will be presented, and vector radiative transfer simulations will be produced to estimate the benefit of this change.

How to cite: Dekemper, E. and Vanhamel, J.: Enhancing the AOTF-based NO2 camera with light polarization sensitivity for aerosol retrievals, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-13464, https://doi.org/10.5194/egusphere-egu23-13464, 2023.

Nitrogen oxides (NO_x, i.e. NO and NO₂) are a major contributor to urban air pollution and have negative impacts on human health, relating to respiratory and cardiovascular problems. NO₂ is also a precursor of secondary particulate matter and tropospheric ozone, which are also associated with adverse effects on human health. Inland waterway vessels are a significant source of NO_x emissions due to their diesel engines operating at high temperatures. Emissions from inland ships are concentrated in the vicinity of waterways, and could be a significant local air pollution source, particularly in residential areas located along intensively used waterways, narrow and steep river valleys, and small villages without heavy road traffic or nearby power plants. Hence, quantifying the influence of inland ship emissions on air quality and humans is important.

We demonstrate the use of ground-based MAX-DOAS (Multi AXis-Differential Optical Absorption Spectroscopy) measurements to estimate NO_x emissions from inland ships on the Rhine River in western Germany. We show that this method can be used to derive ship emissions of NO_x for individual plumes and as an average over several plumes. However, we also identify several challenges with this approach and propose ways to improve it.

The combination of MAX-DOAS and in situ measurements, particularly knowledge of the NO/NO₂ ratio could lead to more accurate estimates of ship emissions. In addition, we introduce planned systematic measurements at selected locations, such as narrow parts of the Rhine and Moselle valleys, where ship emissions may be a major pollution source. We plan to apply regional models to estimate the effect of the updated ship emissions on local NO_x concentrations.

How to cite: Ripperger-Lukosiunaite, S., Ziegler, S., Donner, S., Kuhn, L., Hoffmann, T., Hoor, P., and Wagner, T.: Estimating Nitrogen Oxides emissions from inland waterway vessels using MAX-DOAS measurements – Results of pioneering measurements and plans to advance the method, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-7447, https://doi.org/10.5194/egusphere-egu23-7447, 2023.

High spatial-temporal resolution distribution of atmospheric gaseous pollutant is an important basis for tracing its emission, transport and transformation. At present, methods commonly used to obtain the regional horizontal distribution of trace gas are based on satellite remote sensing or numerous in-situ observation. However, typical trace gas monitoring satellites only have a few fixed overpassing times with a spatial resolution limited to several kilometers, which make it hard to locate minor emission sources. Limited in-situ observations have limited coverage, and can only obtain trace gas concentration information near the observation point. In this study, we propose a method for the long-term detection of the horizontal distribution of trace gas. The spatial resolution in the direction of rotation was up to 0.1°, and the spatial resolution in the optical path direction, reached the kilometer level. Meanwhile, the temporal resolution of the results reached the hourly level during the daytime. The obtained trace gas horizontal distribution was consistent with the in-situ and mobile measurements. Compared with satellite remote sensing, this method achieved horizontal distribution results with higher spatial and temporal resolutions, and located several small high-value areas in Hefei, China. The satellite NO₂ vertical column density (VCD) distribution results were evaluated via the NO₂ horizontal distribution obtained from the hyperspectral NO₂ horizontal distribution at 13:30 (local time) (UTC+8:00) on April 2, 2022. The Tropospheric NO₂ VCD results of the satellite at transit time (13:30) were consistent with the hyperspectral NO₂ horizontal distribution results at 13:00–14:00 on the same day but were not consistent with the daily average NO₂ results. The hourly NO₂ concentration in each area was 10–40% lower than the daytime average obtained by the hyperspectral remote sensing result. Based on these results, we approximated the errors associated with the calculation of NO₂ emissions based on the satellite results, with a maximum bias of approximately 69.45–83.34%.

How to cite: Li, Q., Lu, C., Xing, C., Hu, Q., Tan, W., Li, H., Li, J., Zhang, Z., Chang, B., and Liu, C.: A novel hyperspectral remote sensing technique for horizontal distribution of atmospheric gaseous pollutant: to fill the spatio-temporal resolution limitations of satellite and in-situ observations, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-4611, https://doi.org/10.5194/egusphere-egu23-4611, 2023.

The Tibetan Plateau (TP) plays a key role in regional environment and global climate change, however, the lack of vertical observation hinders a deeper understanding of the atmospheric chemistry and atmospheric oxidation capacity (AOC) on the TP. In this study, we conducted MAX-DOAS measurements at Nam Co, central TP, to observe the vertical profiles of aerosol, water vapor, NO₂, HONO and O₃ from May to July 2019. In addition to NO₂ mainly exhibiting a Gaussian shape with the maximum value appearing at 300-400 m, other four species all showed an exponential shape and decreased with the increase of height. The maximum values of monthly averaged aerosol (0.17 km^-1) and O₃ (66.71 ppb) occurred on May, water vapor (3.68×10¹⁷ molec cm^-3) and HONO (0.13 ppb) appeared on July, while NO₂ (0.39 ppb) occurred on June at 200-400 m layer. Water vapor, HONO and O₃ all exhibited a multi-peak pattern, and aerosol appeared a bi-peak pattern for their averaged diurnal variation. Moreover, we found O₃ and HONO were the main contributors to OH on the TP. The averaged vertical profiles of OH production rates from O₃ and HONO all exhibited an exponential shape, and decreased with the increase of height with the maximum values of 2.61 ppb/h and 0.49 ppb/h at the bottom layer, respectively. In addition, source analysis for HONO and O₃ were conducted based on vertical observations. The heterogeneous reaction of NO₂ on wet surfaces was a significant source of HONO, which obviously associated with water vapor concentration and aerosol extinction. The maximum values of HONO/NO₂ appeared around water vapor being 1.0×10¹⁷ molec cm^-3 and aerosol being lager 0.15 km^-1 under 1.0 km, and the maximum values usually accompanied with water vapor being 1.0-2.0×10¹⁷ molec cm^-3 and aerosol being lager 0.02 km^-1 at 1.0-2.0 km. O₃ was potentially sourced from south Asian subcontinent and Himalayas through long-range transport. Our results enrich the new understanding of vertical distribution of atmospheric components and explained the strong AOC on the TP.

How to cite: Xing, C., Liu, C., and Hu, Q.: Observations of the vertical distributions of summertime atmospheric pollutants in Nam Co: OH production and source analysis, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-4660, https://doi.org/10.5194/egusphere-egu23-4660, 2023.

The status and the most recent developments of the algorithm of the operational TROPOMI (Tropospheric Monitoring Instrument) Ozone Profile product will be presented in this contribution. TROPOMI is the payload onboard of the single-satellite Sentinel-5 Precursor (S5P), an atmospheric composition mission that is part of the EU Copernicus program. The aim of the TROPOMI ozone profile product is to continue the record of the stratospheric ozone, monitor changes, improve the accuracy of the retrieved stratospheric profiles and focus on the tropospheric ozone, which is also important for climate studies. The monitoring of the evolution of stratospheric and tropospheric ozone is important as the ozone plays an important role in atmospheric chemistry and radiative balance throughout the atmosphere. The stratospheric ozone layer from 15 to 50 km absorbs the harmful UV radiation, protecting life at the surface. Tropospheric ozone is a greenhouse gas affecting the climate. In addition, ozone in the lower troposphere is a toxic component of air pollution with significant public health and agricultural impacts.

The operational ozone profile product of TROPOMI provides the ozone profile at 33 pressure levels in the atmosphere and as 6 sub-columns with a vertical sampling depending on the altitude. The ozone profile is derived from the UV spectral range (270-330 nm), with an horizontal spatial resolution of approximately 28x28 km². The derived ozone profile contains 6-7 independent pieces of information, providing a vertical resolution in the range 7 – 15 km. The retrieval is based on the Optimal Estimation method, which combines the information from the measured spectra with the a-priori information. In addition to the a-priori profile, the retrieved profiles and their errors, the algorithm also provides diagnostic information, such as the averaging kernel matrix of the ozone profile elements, an essential parameter also for the product validation operated by the ESA/Copernicus Atmospheric Mission Performance Cluster/Validation Data Analysis Facility (ATM-MPC/VDAF).

The algorithm also relies on accurate Level 1B radiometric calibration of both radiance and irradiance data, which addresses in particular the spectral region below 310 nm. From comparison to other satellites sensors as well as to forward models, it is known that the TROPOMI UV spectral bands show systematic radiometric deviations. To address this issue, a radiometric correction based on a comparison with forward models has been developed. The derived correction parameters are updated regularly in the operational product in order to follow the changes of the instrument over time due to its optical degradation.

The improvements in the operational algorithm, regarding the radiometric calibration and the choice of a new climatology for the ozone profile a-priori information and its uncertainty, are crucial aspects for the ozone retrieval and they will be shown during this talk.

Finally, with the availability of the reprocessed ozone profile data from the beginning of the mission, this contribution will also show the results of the algorithm performances throughout the TROPOMI mission, in ozone hole conditions and for tropospheric enhancements.

How to cite: Di Pede, S., Veefkind, P., Sneep, M., ter Linden, M., and Keppens, A.: The TROPOMI Ozone Profile retrieval algorithm and its use for stratospheric and tropospheric atmospheric research, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-11861, https://doi.org/10.5194/egusphere-egu23-11861, 2023.

African megacities suffer from air pollution and the problem is expected to worsen in the near-future, with the ongoing explosive demographic growth in these areas. The sources of pollutants in Africa are different from those found in Europe. Agricultural burnings and charcoal-based cooking largely contribute to the NO2 and HCHO burdens. However, many large African cities, such as the City of Kinshasa, capital of the Democratic Republic of Congo, do not have local pollution monitoring capabilities. In these polluted places, space-based measurements are often the only source of data available regarding air quality. Together with the validation of TROPOMI in a poorly sampled area, this context motivated ground-based DOAS observations in Kinshasa since 2017. We first operated a single-axis instrument, which we upgraded as a MAX-DOAS instrument in December 2019.  

We describe the observation site in Kinshasa, the MAX-DOAS instrument, and the retrievals which use the algorithmic tools developed within the FRM4DOAS project. We compare the MAX-DOAS database (2019-2023) of ground-based observations of aerosol optical thickness (AOT), NO2 and HCHO with MODIS and TROPOMI, and with simulations using the GEOS-CHEM Chemistry and Transport Model. Such comparisons enable to assess the quality of the satellite products and model performances around Kinshasa. The ground and satellite-based observations have different sensitivities to the trace gas profiles. Combining the observations and model datasets sheds light on the true atmospheric state above Kinshasa. Another objective of this work is to constrain emission inventories in central Africa. 

How to cite: Merlaud, A., Yombo Phaka, R., Pinardi, G., Mbungu Tsumbu, J.-P., Bopili Mbotia Lepiba, R., Lomami Djibi, B., Friedrich, M., De Smedt, I., Stavrakou, J., Muller, J.-F., Hendrick, F., Mahieu, E., and Van Roozendael, M.: MAX-DOAS measurements of AOT, NO2 and HCHO in Kinshasa (DR Congo): comparisons with TROPOMI and GEOS-CHEM, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-13645, https://doi.org/10.5194/egusphere-egu23-13645, 2023.

ALTIUS (Atmospheric Limb Tracker for the Investigation of the Upcoming Stratosphere) is an atmospheric limb mission being implemented in ESA's Earth Watch programme and planned for launch in early 2026. The primary objective of the mission is to measure high-resolution stratospheric ozone concentration profiles. Secondary objectives are the retrievals of stratospheric aerosols particle density, NO₂, water vapor and other minor species concentrations.

This innovative instrument consists of three spectral high-resolution imagers: UV (250-355 nm), VIS (440-675 nm) and NIR (600-1040 nm) channels. The UV channel uses a stack of four Fabry-Pérot interferometers, while the VIS and NIR channels each rely on an AOTF (Acousto-Optical Tunable Filter). Each channel can image scenes independently of the others at given wavelengths and with a moderate spectral resolution, and high spatial sampling. The agility of ALTIUS allows for series of observations at desired wavelengths carefully chosen to retrieve the vertical profiles of species of interest.

The instrument will perform measurements in different geometries to maximize global coverage: observing limb-scattered solar light in the dayside, solar occultations at the terminator, and stellar, lunar, and planetary occultations in the nightside.

The status of the ALTIUS mission will be presented as well as the foreseen quality of the Level-1 observations.  The quality of the retrieved profile densities will be discussed with a particular focus on the high vertical resolution that can be achieved using this instrument. The added-value of the native imaging capabilities of ALTIUS in terms of observations, and in-flight calibrations, will be highlighted.

How to cite: Berthelot, A., Baker, N., Demoulin, P., Errera, Q., Franssens, G., Fussen, D., Mateshvili, N., Pieroux, D., Sotiriadis, S., and Dekemper, E.: The ALTIUS mission: status and performance, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-14246, https://doi.org/10.5194/egusphere-egu23-14246, 2023.

Current and planned satellite missions such as the Japanese GOSAT (Greenhouse Gases Observing Satellite) and NASA’s OCO (Orbiting Carbon Observatory) series and the upcoming Copernicus Carbon Dioxide Monitoring (CO2M) mission aim to constrain national and regional-scale emissions down to scales of urban agglomerations and large point sources. The CO2Image demonstrator mission of the German Aerospace Center (DLR) is specifically designed to detect and quantify carbon dioxide (CO₂) and methane (CH₄) emissions from medium-size point sources. To this end its COSIS (Carbon dioxide Sensing Imaging Spectrometer) push-broom grating spectrometer measures reflected solar radiation with a high spatial resolution of 50x50 m², covering tiles of ~50x50 km² extent. The instrument has a moderate spectral resolution of approximately ~1 nm and observes in a single spectral window in the 2 µm region.

Here we present and discuss the impact of the expected COSIS performance on the retrieved level-2 data. The level-1 data (spectra) are generated using the Py4CAtS (Python for Computational ATmospheric Spectroscopy) line-by-line radiative transfer model and the COSIS SIMulator (COSIS-SIM). Based on the COSIS instrument parameters the analysis examines the retrieval errors related to noise which allows to estimate the detection and quantification limit of CO₂ and CH₄ emission rates at the instrument’s spatial and spectral resolution. We further discuss the effect of heterogeneous scenes, i.e. high contrast surfaces that cause an effective distortion of the spectral response function by non-uniform illumination of the entrance slit. Finally, we assess the influence of initial guess values for the plume's vertical extent and shape on the retrieval.

How to cite: Hochstaffl, P., Baumgartner, A., Slijkhuis, S., Lichtenberg, G., Koehler, C. H., Schreier, F., Roiger, A., Feist, D. G., Marshall, J., Butz, A., and Trautmann, T.: CO2Image retrieval studies and performance analysis, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-15635, https://doi.org/10.5194/egusphere-egu23-15635, 2023.