Orals: Thu, 7 May, 08:30–10:15 | Room 1.61/62
The Copernicus Sentinel-4/UVN and Sentinel-5/UVNS imaging spectrometers, hosted on EUMETSAT’s Meteosat Third Generation - Sounder (MTG-S) and EUMETSAT Polar System - Second Generation A (EPS-SG A) satellites, are in space since the summer of 2025. Sentinel-4/UVN is designed to monitor atmospheric trace gases - such as ozone, nitrogen dioxide, sulphur dioxide, formaldehyde and glyoxal - as well as aerosol and cloud properties from hyperspectral measurements in the UV, Visible and Near-Infrared (UVN). Observing from a geostationary orbit, it provides high spatial resolution and hourly coverage over Europe and northern Africa. Sentinel-5/UVNS has a similar scope but additionally covers spectral bands in the Shortwave-Infrared and therefore allows measuring additional species, such as carbon monoxide and methane. Flying in a polar orbit, it provides high spatial resolution and near-daily global coverage. Both instruments provide essential data for tracking atmospheric composition and support the Copernicus Atmosphere Monitoring Service (CAMS). The innovative instruments are completing the European contribution to the constellation of geostationary and polar orbiting atmospheric composition missions, including the existing geostationary GEMS and TEMPO over Asia and North America, respectively, as well as the fleet of Low Earth Orbit air quality missions operating in similar spectral ranges, such as GOME-2, OMI, TROPOMI and OMPS. This presentation will cover the mission status during the ongoing commissioning and Cal/Val activities, including insights into level-2 product status.
How to cite: Lindstrot, R., Garcia, S., Rüthrich, F., Keppler, M., Hao, N., Köhler, P., Diekmann, C., Kumar, V., Gu, M., Taberner, M., Hayer, C., Caseiro, A., Wang, Y., Poli, G., Munro, R., Grandell, G., and Bojkov, B.: Europe's new atmospheric chemistry missions in space: The Path to Operations of Copernicus Sentinel-4/UVN and Sentinel-5/UVNS., EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-22384, https://doi.org/10.5194/egusphere-egu26-22384, 2026.
We present a status overview of the TEMPO mission including its operation, validation and
status of baseline data products and recent algorithm improvements, development of Near-Real-
Time (NRT) and other research data products, science and application highlights.
TEMPO is the North America component of the geostationary (GEO) air quality constellation
along with GEMS over Asia and Sentinel-4 over Europe. It is the first spaceborne instrument
providing hourly daytime air pollution over North America at neighborhood scale (~10 km 2 at
boresight). It uses UV/visible spectroscopy to measure key elements of tropospheric air pollution
chemistry including O 3 , NO 2 , HCHO and aerosols, and capture the inherent high variability in the
diurnal cycle of emissions and chemistry. At night, TEMPO can observe city lights, gas flaring,
maritime lights, clouds and snow in the moonlight, lightning, aurorae, and nightglow without
interfering with its primary daytime air quality mission. After the successful launch of TEMPO
on board IS-40E into the GEO orbit at 91W in April 2023, it conducted its first light
observations in early Aug. 2023 and started its nominal operation in Oct. 2023, kicking off a new
era of air quality monitoring from space over North America. It finished its 20-month of baseline
Phase E in June 2025. The baseline mission has been extended to Sep. 2026, with further
extension via a NASA senior review in early 2026. Baseline V3 data products were released to
the public in May 2024 from NASA’s ASDC. A significantly improved V4 data products were
released to the public in early Sep. 2025, including the first public release of the ozone profile
product. TEMPO NRT data products with data latency of 2-3 hours and other science quality
data products were funded by NASA Satellite Needs Working Group (SNWG) to assist in air
quality forecasting and modeling efforts and develop better pollution control strategies. NRT
products (V2, based on baseline V4) were also released to the public for the first time in early
Sep. 2025. Many other research data products have been produced by the science community and
TEMPO data products have been widely used by the user community including nearly 700 early
adopters.
How to cite: Liu, X.: A New Era of Air Quality Monitoring from Space over North America with TEMPO:Mission Status from Early Years in Orbit, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-23278, https://doi.org/10.5194/egusphere-egu26-23278, 2026.
Aerosol Layer Height (ALH) is an important parameter for climate studies, air quality monitoring, aviation safety near volcanos and remote sensing of trace gases. The ALH is rapidly becoming available from many new sources, such as polar orbiting satellites like TROPOMI, EarthCARE, Sentinel-3 and 5, and geostationary instruments around the globe, such as GEMS, TEMPO and Sentinel-4. These instruments provide many opportunities, covering a large range of spatial and temporal scales, that are further strengthened by a number of regional lidar networks around the globe, like the Latin American Lidar Network (LALINET), the Asian dust and aerosol lidar observation network (AN-Net), Micro-Pulse Lidar Network (MPLNET) and the European Aerosol Research Lidar Network (EARLINET). The above-mentioned geostationary instruments have the unique capability of providing the temporal variation of ALH and other parameters during the day over a large area, and lidar stations and other ground-based layer height providing instruments can be used to compare and validate the hourly retrievals and their temporal variation. However, the instruments are not overlapping and so cannot be compared directly. Comparison between geostationary instruments must be performed by polar orbiting satellites covering the field of views of geostationary instruments, preferably by satellites with different local overpass times, to cover as much as possible the temporal variation over the day.
The validation of the various ALH products suffers from a number of issues, next to instrument calibration most notably different measurement techniques, like e.g. oxygen absorption spectroscopy, polarization techniques, stereo photogrammetry or active sensing, and the spatial and temporal coverage of satellite instruments. Here, we provide an overview of the issues and opportunities that are available for ALH comparison and validation from the polar orbiting satellites Sentinel-5p and EarthCARE. Intercomparisons between ATLID average extinction profiles (like a weighted or effective extinction height) and ALH from TROPOMI, GEMS and Sentinel-3 will be shown, to illustrate the possibilities for validation of TEMPO, S4 and S5, and the possibility to intercompare these various geostationary satellites. It will demonstrate the issues that arise from different layer height definitions that exist between the instruments, and that cause problems especially when the extinction profiles become complicated (like e.g. in the case of multiple vertical layers).
Theoretical treatment of the aerosol layer height problem will be combined with examples of ATLID extinction profiles, showing well-defined and less well-defined layer heights and their associated problems for ALH retrievals.
How to cite: de Graaf, M., Veefkind, J. P., Sneep, M., and ter Linden, M.: Intercomparison of aerosol layer height between geostationary and polar orbiting satellites, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-9195, https://doi.org/10.5194/egusphere-egu26-9195, 2026.
In this presentation TEMPO NO2 observations are evaluated with a focus on snow-covered surfaces. Its ability to capture sharp spatial and temporal gradients in NO2 vertical column densities (VCDs) and surface concentrations are assessed, which are key parameters for assessing air quality and public health impacts. Data from the 2024 Study of Winter Air Pollution in Toronto (SWAPIT), including in situ and mobile MAX-DOAS measurements, are used to assess TEMPO’s precision and accuracy. Additional evaluations are performed at Pandora sites across North America to examine wintertime performance. Comparisons show strong correlations between TEMPO and surface observations, with significant improvements in bias after applying corrections to air mass factors, cloud fraction, and surface albedo (from -32% to -9% over snow).
How to cite: Griffin, D., Zhao, X., McLinden, C., Yazdani, N., Nowlan, C., Gonzalez Abad, G., Fioletov, V., Galarneau, E., Mihele, C., Wren, S., and Su, Y.: High-Frequency Nitrogen Dioxide Observations over Snow-Covered Surfaces from TEMPO and Ground-Based Measurements, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-14289, https://doi.org/10.5194/egusphere-egu26-14289, 2026.
Tropospheric nitrogen dioxide (NO2) is a key indicator of nitrogen oxide (NOx) emissions and atmospheric chemical processes. Tropospheric NO2 columns retrieved from instruments in low Earth orbit (LEO), such as OMI and TROPOMI, have been extensively used to investigate the spatial and temporal variability of NOx emissions. However, they typically have only one overpass per day and location, with the availability of data being further reduced due to the presence of clouds. The new geostationary instruments, GEMS, TEMPO, and Sentinel-4, enable the observation of atmospheric trace gases with hourly temporal resolution. The Geostationary Environmental Monitoring Spectrometer (GEMS), launched in February 2020, is the longest-operating and provides hourly daytime observations of NO2 with a spatial resolution of 3.5 x 8 km2 over a large part of Asia.
In this study, four years of GEMS IUP-UB tropospheric NO2 column data have been analyzed to investigate the seasonal and weekday-dependent diurnal variability of NOx emissions and lifetime for several emission sources within the GEMS domain. The resulting hourly emission and lifetime estimates are used to assess emission inventories and atmospheric models. For some emission sources, such as Seoul, seasonal emissions differ in magnitude and diurnal pattern, whereas other locations, such as Singapore, show almost no seasonal variation and small diurnal variation. Weekday-to-weekend differences are analyzed on an hourly basis, revealing a clear weekend effect, with small diurnal differences for most analyzed emission sources. Hourly emission profiles used in emission inventories and air quality models are compared with the GEMS-based emission estimates, providing observational constraints on the representation of diurnal NOx emissions in current atmospheric chemistry models. GEMS-based hourly lifetime estimates are compared to WRF-Chem model results.
How to cite: Lange, K., Richter, A., Burrows, J. P., Bösch, H., Kim, S.-W., and Seo, S.: Seasonal and weekday-dependent diurnal variability of NOx emissions and lifetimes from hourly GEMS NO2 observations , EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-14436, https://doi.org/10.5194/egusphere-egu26-14436, 2026.
Nitrous acid (HONO) is a key atmospheric species primarily due to its role as a source of OH through its rapid photolysis. OH is the atmosphere’s primary oxidant: it plays a central role in breaking down pollutants and greenhouse gases, and at the same time, it is a key ingredient to photochemical smog and ozone formation. Despite recent scientific progress, the emission budget and formation mechanisms of HONO are poorly constrained and consequently the impact of HONO emissions on tropospheric chemistry remains uncertain although it is believed to be important.
With the advent of high-spatial resolution hyperspectral space sensors, it becomes possible to detect short-lived species as HONO from large emission sources such as fires. This has been demonstrated on the global scale using the Sentinel-5 Precursor/TROPOMI instrument. Hourly observations from geostationary instruments, like GEMS and TEMPO, with a similar or even better spatial resolution than TROPOMI, opens new possibilities in terms of research and algorithmic developments. Understanding the time evolution of HONO emissions and conversion into NOx and how this relates to the fire activity and plume composition is particularly interesting.
Here, we present our progress in improving and interpreting HONO space-based data. We focus not only on HONO but also on the retrieval of NO2 in the same spectral range as HONO, using an innovative algorithm (CO-DOAS). The objective is to estimate the enhancement ratio of HONO to NO2 andstudy its relation to the fire intensity both in space and time. We also assess the consistency of GEMS and TEMPO HONO (and HONO/NO2) results with TROPOMI observations.Finally, we briefly discuss the possibility of new HONO observations from future satellite platforms.
How to cite: Theys, N., Cha, H., De Smedt, I., Yu, H., Vlietinck, J., Danckaert, T., Kim, J., and Van Roozendael, M.: Hourly observations of HONO and NO2 in fire plumes as detected by GEMS and TEMPO, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-10427, https://doi.org/10.5194/egusphere-egu26-10427, 2026.
The PEGASOS project (Product Evaluation of GEMS L2 via Assessment with Sentinel-5P and other Sensors) provides comparisons for GEO L2 data with measurements from LEO instruments and ground-based networks. The main focus is on the evaluation of the operational GEMS and TEMPO L2 data products total Ozone, tropospheric and stratospheric NO2, as well as cloud- and aerosol parameters like cloud fraction, cloud pressure, aerosol index and aerosol layer height. For the evaluation of those GEMS and TEMPO L2 products, comparisons with space-borne instruments rely mainly on TROPOMI/S5P and GOME-2/MetOP-BC, and on ground-based measurements/networks like Dobson, Brewer, Max-DOAS etc.
In this contribution we provide an overview of the current PEGASOS project status and we summarize the activities performed so far for evaluating the GEMS and TEMPO L2 data products mentioned above. The ESA-funded PEGASOS project is coordinated by the German Aerospace Center (DLR) and the consortium is completed by the Aristotle University of Thessaloniki (AUTH), the Royal Belgian Institute for Space Aeronomy (BIRA-IASB), and the Institute for Environmental Physics of the University of Bremen (IUP-UB).
How to cite: Lutz, R., Loyola, D., and Hummel, T. and the PEGASOS team: The PEGASOS project: Evaluation of Geo-Ring data with LEO and ground based measurements, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-13626, https://doi.org/10.5194/egusphere-egu26-13626, 2026.
Since the launch of TEMPO in 2023, the NOAA Office of Oceanic and Atmospheric Research (OAR) has conducted airborne field campaigns with support from the NOAA National Environmental and Satellite Data Information Service (NESDIS). The 2023 AEROMMA (Atmospheric Emissions and Reactivity Observed from Megacities to Marine Areas) campaign surveyed major urban areas in North America, including Los Angeles, Chicago, Toronto, and New York, with the heavily instrumented NASA DC-8. The 2024 and 2025 AiRMAPS (Airborne and Remote Sensing Multi Air Pollutant Surveys) campaigns surveyed urban areas of Denver, Salt Lake City, and Baltimore–Washington DC, in addition to oil and gas basins in Colorado, Utah, and the mid-Atlantic region of the U.S., with the NOAA Twin Otter and ground-based mobile laboratories.
Here, we present several results from these campaigns. In 2023, widespread smoke impacts from a record-breaking Canadian wildfire season coincided with AEROMMA, providing extensive in-situ observations of smoke, ozone, and its precursors. Vertically-resolved measurements from research flights in Chicago provided constraints on the influence of these fires on urban ozone. The 2024 Utah Summer Ozone Study measured ozone and its precursors in Salt Lake City from a mobile laboratory and the NOAA Twin Otter. Photochemical box modeling and radiative transfer modeling in both cities quantified the effects of ozone transport, local photochemistry, and aerosol shading. These results add to a growing database to quantify the fire influence on ozone in North American cities. Surveys of urban areas and oil and gas basins using a novel airborne Doppler lidar mass balance method have provided new emissions quantification for methane, nitrogen oxides, and other trace gases. These determinations can be compared to emissions estimates from satellite and airborne remote sensing to cross-validate these methods.
How to cite: Brown, S., Chace, W., Schafer, N., Malarich, N., Baidar, S., Ren, X., Warneke, C., and Womack, C.: Airborne field campaigns in the geostationary satellite era in North America: Results from AEROMMA and AiRMAPS, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-15703, https://doi.org/10.5194/egusphere-egu26-15703, 2026.
Geostationary platforms can provide high spatial and temporal resolution measurements of air quality parameters. To date, there is an acute absence of geostationary observations over Africa, the Middle East, South America and Oceania, even though these regions tend to be poorly monitored and are undergoing dramatic changes in emissions and air quality. Here we present the results of a study and white paper outlining the benefits of expanding geostationary observations to these regions. The white paper explores the current state of measurements, technology, data availability, and the feasibility of implementing such observations to improve environmental monitoring and decision-making in these regions. Additionally, the paper discusses the potential impact of such observations on policymaking, public health, and environmental mitigation efforts in the four regions. Some of the parameters sought for high temporal and spatial observation frequency include: O3, NO2, Particulates, and others discussed in the Atmospheric Composition Virtual Constellation (AC-VC) White Papers and currently observed from geostationary platforms by the TEMPO (Tropospheric Emissions: Monitoring of Pollution) and GEMS (Geostationary Environment Monitoring Spectrometer) instruments. These observations are vital in closing the gap in air quality data for improving global air quality models and hemispheric pollution transport. Additional benefits include environmental monitoring in developing regions, aiding in pollution control efforts, and supporting environmental change mitigation strategies through advanced satellite technology.
How to cite: Omar, A., Levelt, P., Kondragunta, S., Artaxo, P., daSilva, A., Drobot, S., Hickman, J., Lefer, B., Nicks, D., Suleman, R., Veihelman, B., Worden, H., Shams, S., Wang, J., Knowland, E., Hannigan, J., Cooper, O., Nassar, R., and Czyzewska, D.: Expanding Geostationary Atmospheric Composition Satellite Constellation: Towards Global Coverage , EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-3559, https://doi.org/10.5194/egusphere-egu26-3559, 2026.
BAE Systems has two geostationary air quality instruments that are currently part of the Geo-Ring North, TEMPO and GEMS. The TEMPO mission was intended to demonstrate the ability and usefulness of hourly measurements of air quality, pollution sources, transport and chemistry over North America. BAE Systems recently finished a study and an initial contract to replace TEMPO with an updated instrument with more capability and minimal changes to heritage. This paper will review the TEMPO mission and the updates to the design, calibration, and capability of future ACX-like instrument. It will highlight how the improved capabilities could enhance the existing and future global monitoring system.
How to cite: Delker, T., Nicks, D., Drobot, S., Farris, B., and Baker, B.: BAE Systems updates from the GeoXO Atmospheric Composition Instrument and application to future instruments, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-4130, https://doi.org/10.5194/egusphere-egu26-4130, 2026.
The deployment of spectrometers on geostationary satellites has enabled unprecedented hourly monitoring of trace gases critical for air quality and atmospheric research. As the dominant species of global BVOC emissions, isoprene has significant implications for health, weather and climate. Field studies have shown that isoprene emission rates increase with temperature until reaching a peak and subsequently decrease. Using TEMPO’s hourly HCHO columns with ERA5 temperature data, we investigate the temperature dependency of HCHO, a proxy for isoprene emissions, across vegetated regions of North America. After accounting for confounding variables such as biomass burning and soil moisture, we apply Pettitt’s test to detect the change-point where correlation between HCHO concentration and temperature shifts from positive to negative. We find distinct turn-over behavior of HCHO columns across diverse regions with different dominant vegetation types, including broadleaf evergreen trees, broadleaf deciduous trees, needleleaf evergreen trees and crops with corresponding temperature thresholds (most significant) of approximately 305.5 K, 306.1 K, 305.6 K and 303.7K, respectively. To ensure statistical robustness, we perform a bootstrap-based Pettitt’s test approach to quantify the uncertainty of these thresholds. The resulting 95% confidence intervals (CI) are [305.97, 306.37] K for broadleaf evergreen trees, [305.49, 306.28] K for broadleaf deciduous trees, [305.60, 305.70] K for needleleaf evergreen trees, and [302.33, 303.06] K for crops, respectively. This marks the first satellite-based detection of such a phenomenon. Our study demonstrates the exceptional potential of Geo-Ring observations, particularly TEMPO’s diurnal sampling, in detecting and constraining biogenic emissions. These findings underscore the value of geostationary data for refining emission models and enhancing predictions of atmospheric composition under a changing climate.
How to cite: Luan, X., Li, X., Zhang, X., Fu, T.-M., and Zhu, L.: Turn-over Effect of Biogenic HCHO Columns at High Temperatures Seen by TEMPO Satellite, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-2698, https://doi.org/10.5194/egusphere-egu26-2698, 2026.
Deterioration of air quality affects human health and socioeconomic conditions. An air quality early warning system (EWS) providing timely information prior to hazardous events is essential for minimizing associated damage and adverse impacts on human health. This study presents an air quality EWS that enables air quality nowcasting using high-resolution observations from Geostationary Environment Monitoring Spectrometer (GEMS). This system is delivered through a mobile application to facilitate wider dissemination of EWS. Southeast Asia is selected as the research region for early warning of trace gases (i.e., aerosol, NO2, and O3) where air quality deteriorates during the dry season. The results are generated using satellite-based observations and are presented through an intuitive mobile application interface. A direct satellite-to-mobile dissemination framework is implemented, allowing rapid transmission of alerts via Cell Broadcast Service (CBS), Short Message Service (SMS), and push notifications. The developed EWS is expected to contribute to disaster risk reduction, climate change adaptation, and the achievement of the Sustainable Development Goals (SDGs). Moreover, this system is scalable to a global extent in regions where Geo-Ring satellite data are available, supporting enhanced response capacities in air quality vulnerable regions.
How to cite: Kim, G. and Choi, Y.-S.: Early warning system for air quality based on geostationary satellite observations, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-6215, https://doi.org/10.5194/egusphere-egu26-6215, 2026.
Accurate quantification of tropospheric nitrogen dioxide (NO₂) at high spatial resolution is crucial for monitoring air pollution emissions and validating the environmental satellites, including the GEMS (Geostationary Environment Monitoring Spectrometer). In this study, we present the retrieval and analysis of high-resolution NO₂ Vertical Column Densities (VCDs) using airborne hyperspectral observations from the EMSA (Environmental Monitoring Spectrometer for Aircraft) over Yeosu’s industrial complexes in Korea
To ensure retrieval accuracy, Level 1B spectra were first generated through precise radiometric calibration, spectral calibration, and geometric (INR) correction. The NO₂ Slant Column Densities (SCDs) were retrieved using the QDOAS algorithm with an optimized spectral fitting window (420–460 nm) selected to minimize interference. These SCDs were subsequently converted to Vertical Column Densities (VCDs) using Air Mass Factors (AMFs) calculated by the VLIDORT radiative transfer model, incorporating aerosol properties and surface albedo data.
Finally, the airborne NO₂ VCDs were compared with coincident GEMS measurements. The preliminary analysis reveals a consistent spatial distribution between the high-resolution airborne data and satellite observations, particularly in capturing point-source emissions. This study demonstrates that EMSA observations effectively resolve local emission sources unresolved by satellites, serving as a valuable reference dataset for validating GEMS Level 2 products. Detailed validation statistics, including correlation analysis with GEMS, will be presented.
How to cite: Choi, H.: Retrieval of High-Resolution Tropospheric NO₂ VCDs from Airborne EMSA Observations over the Industrial Areas in Yeosu, Korea, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-8802, https://doi.org/10.5194/egusphere-egu26-8802, 2026.
Optical path length reaching to satellite sensor is affected by changes of aerosol layer altitude. Based on this principle, Aerosol Effective Height (AEH) from the GEMS is retrieved by using the O4 Slant Column Density (SCD) variation. AEH retrieval algorithm is being improved up to V3.0. This algorithm uses a Look-up Table (LUT) to convert O4 SCD, which is calculated directly from GEMS L1C data, into AEH. O4 SCD is retrieved by DOAS fitting and AEH is inversely estimated by comparing O4 SCD, aerosol properties, and geometry to LUT.
In this study, we discuss changes resulting from the update of AEH algorithm V2.1 to V3.0. This update is mainly about correcting atmospheric profile, which is based on the US Standard Atmosphere. O4 Vertical Column Density (VCD) shows seasonal and spatial differences and temperature-dependent (Choi et al., 2019). Using variable O4 VCD can be suitable for realistic atmospheric condition. O4 VCD can be derived from surface pressure, temperature, and relative humidity (Beirle et al., 2022). We corrected the O4 VCD by applying the ratio of monthly mean temperature and pressure from ECMWF ERA5 from 2019 to 2023 relative to the US Standard value.
After update, AEH decreased in India and Southeast Asia, while it slightly increased in Northeastern China and Korea. Compared to TROPOMI Aerosol Layer Height (ALH), March 2021, the bias decreased by approximately 0.5 km compared to V2.1. Although algorithm update results retrievals in stable range, there are changes in retrieval coverage and regional differences. Therefore, further research is required to investigate these regional differences.
How to cite: Lee, S., Kim, M., and Park, S. S.: Update of GEMS AEH algorithm V2.1 to V3.0 based on O4 VCD correction, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-9573, https://doi.org/10.5194/egusphere-egu26-9573, 2026.
The three-dimensional (3D) cloud radiative effect, specifically radiance contributions via horizontal photon transport from neighboring clouds that operational algorithms cannot capture, is a significant source of structural uncertainty in trace gas retrievals from Low Earth Orbit (LEO) sensors like TROPOspheric Monitoring Instrument (TROPOMI) and Orbiting Carbon Observatory-2 (OCO-2). Our previous studies have shown that these biases are dependent on Solar Zenith Angle (SZA) due to elongated optical paths at high angles. This dependence presents a critical challenge for the new generation of geostationary (GEO) satellites, specifically the Geostationary Environment Monitoring Spectrometer (GEMS) and Tropospheric Emissions: Monitoring of Pollution (TEMPO). While LEO instruments typically favor low SZA overpasses to maximize signal-to-noise ratios, GEO sensors observe the full diurnal evolution of trace gases. This necessitates measurements at high SZA (low sun elevation), where the 3D cloud effect becomes particularly pronounced.
Furthermore, GEMS and TEMPO deviate from the heritage O2 A-band (760 nm) pressure and cloud properties retrievals used by TROPOMI and OCO-2, instead relying on O2-O2 dimer absorption at 477 nm. This shift introduces distinct radiative transfer challenges, as O2-O2 absorption scales with the square of pressure due to its collisional nature and exhibits different sensitivities to aerosol layering. This study analyzes the 3D cloud radiative effect specific to GEO viewing geometry and gas retrieval products utilizing O2-O2 bands. Specifically, we evaluate the potential for artificial diurnal bias in retrieved NO2 caused by the interplay of changing solar geometry and the 3D cloud effect, and we assess the effectiveness of current Air Mass Factor (AMF) correction strategies for the O2-O2 based retrieval algorithm in the vicinity of clouds.
How to cite: Chen, Y.-W., Schmidt, S., Chen, H., and Massie, S.: The Impact of 3D Cloud Radiative Effect on Trace Gas Retrievals: Bridging the Gap from Low Earth Orbit to Geostationary Missions, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-13240, https://doi.org/10.5194/egusphere-egu26-13240, 2026.
Satellite-based remote sensing has significantly advanced our understanding of global tropospheric nitrogen dioxide (NO2) over recent decades. Complementing the daily global observations from low-earth-orbiting (LEO) satellites, new geostationary (GEO) missions offer high temporal resolution with multiple observations per day, enabling detailed monitoring of diurnal NO2 variability driven by emission patterns and complex atmospheric chemistry. The emerging "Geo-Ring" constellation, comprising GEMS (Asia), TEMPO (North America), and Sentinel-4 (Europe), establishes a powerful framework for regional-to-continental air quality monitoring.
In this study, we address key challenges in NO2 retrievals from GEO satellite observations by proposing two primary methodological improvements: (1) advanced NO2 slant column retrievals, and (2) refined stratospheric correction techniques. An improved NO2 retrieval algorithm is applied to GEMS and TEMPO data. First, we conduct round-robin tests of NO2 slant column retrievals using three different approaches: classical Differential Optical Absorption Spectroscopy (DOAS), Covariance-based DOAS, and a hybrid method combining physics-based retrievals with machine learning. These advanced approaches specifically address issues related to de-striping and retrieval accuracy in inhomogeneous scenes, which is critical for GEO sensors that often lack continuous coverage of clean background regions. For the stratosphere-troposphere separation, challenges specific to GEO sensors, arising from restricted clean reference areas and pronounced diurnal variability, are investigated using two methods: an advanced reference sector approach and stratospheric NO2 estimates derived from CAMS forecast model data.
The improved GEO NO2 retrieval algorithm applied to GEMS and TEMPO observations is evaluated through comparisons with current operational product (GEMS v4.0.1 and TEMPO v4.0) as well as LEO satellite data from TROPOMI and GOME-2. The results demonstrate that the enhanced GEO retrieval algorithm effectively addresses challenges associated with high temporal sampling and the limited availability of clean background sectors, leading to improved retrieval accuracy and reduced uncertainties. These improvements strengthen the consistency between GEO and LEO NO2 products and enhance the interpretation of pollution evolution and diurnal air quality variability.
How to cite: Seo, S., Heue, K.-P., Alvarado, L., Lutz, R., and Loyola, D.: Improved NO2 column retrievals for geostationary satellites: application to GEMS and TEMPO, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-13754, https://doi.org/10.5194/egusphere-egu26-13754, 2026.
The Unified Forecast System with Chemistry (UFS-Chem) model is currently being developed at NOAA to provide research-to-operations capability for atmospheric composition applications. Using UFS-Chem, we perform modeling simulations during the Atmospheric Emissions and Reactions Observed from Megacities to Marine Areas (AEROMMA) 2023 airborne field campaign. During the campaign, Canadian wildfire smoke significantly degraded air quality in the Upper Midwest and Northeast US, including high ozone anomalies. Simulations are at the global scale, and include full gas-chemistry (from the GFDL AM4.1 model) connected with GOCART aerosols at relatively coarse resolution (1 degree vs 1 degree). Wildfire emissions are from the Blended Global Biomass Burning Emissions Product (GBBEPx), which is fire radiative power (FRP) based, and modified with emission coefficients constrained to FIREX-AQ field campaign observations. We evaluate the advection and transport of smoke with retrievals from the Tropospheric Emissions: Monitoring of Pollution (TEMPO) satellite instrument, including for nitrogen dioxide (NO2), formaldehyde (HCHO), aerosol optical depth (AOD), and aerosol layer height (ALH). TEMPO satellite operators are utilized from and/or developed for the Joint Effort for Data assimilation Integration (JEDI). We also evaluate NO2/HCHO and NO2/AOD as a diagnostic for flaming versus smoldering emissions, a key determinant in the chemical speciation of smoke. Preliminary evaluation of UFS-Chem with TEMPO NO2 suggests that the primary emissions of flaming smoke may be off between oxidized (e.g., NOx) and reduced nitrogen species (e.g., NH3). Lastly, we also perform higher-resolution global simulations (25 km x 25 km) of the soon to be operationally implemented Global Chemistry and Aerosol Forecast System (GCAFS) version 1. These simulations do not include gas-phase chemistry, and are used to assess the impact of spatial-resolution on plume-rise and advection of smoke with TEMPO aerosol products. In addition to geostationary satellite products, evaluations are made with ground-based observations, and airborne AEROMMA measurements to assess the skill of UFS-Chem and GCAFS.
How to cite: McDonald, B., Bruckner, M., Lyu, C., Wang, S., He, J., Schwantes, R., Cooper, O., Zhang, L., Schnell, J., Ahmadov, R., Naik, V., Horrowitz, L., Baker, B., Martin, C., Yang, F., Zhang, H., Li, F., Abdioskouei, M., and Barre, J.: Evaluating NOAA’s Unified Forecast System with TEMPO Trace Gas and Aerosol Products, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-15077, https://doi.org/10.5194/egusphere-egu26-15077, 2026.
The Geostationary Environment Monitoring Spectrometer (GEMS) onboard the GEO-KOMPSAT-2B satellite provides high spatiotemporal resolution observations of various atmospheric constituents over East Asia, including ozone, its precursors (NO2, HCHO), SO2, and aerosols. The GEMS total ozone retrieval algorithm (O3T), based on the TOMS Version 9 look-up table approach, was recently updated to Version 2.2 in December 2024. However, the current GEMS total ozone product has shown a systematic underestimation compared to other satellite observations, such as TROPOMI and OMI, as well as ground-based measurements, mainly due to limitations in the Level 1C (L1C) irradiance data.
To address these issues, we evaluate the O3T algorithm using two types of updated L1C datasets: one applying only the bidirectional transmittance distribution function (BTDF) correction (A1), and another applying both the BTDF and degradation corrections (A2). The results show that the use of both A1 and A2 substantially reduces the underestimation of total ozone, with particularly pronounced improvements at high ozone levels. Furthermore, when using A2, the retrieved total ozone exhibits improved long-term stability. Using these improved GEMS total ozone products, we analyze the characteristics and variability of total ozone over East Asia. In addition, we investigate the impact of cloud information, another critical input to the O3T algorithm, on the total ozone retrieval. These results enhance the reliability of GEMS ozone retrievals and provide a foundation for further algorithm optimization.
How to cite: Lee, H., Kim, J.-H., Bak, J., and Hong, S.: Update Plan for GEMS Total Column Ozone: L1C irradiance and Cloud Parameter Improvements, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-18872, https://doi.org/10.5194/egusphere-egu26-18872, 2026.
The NASA Tropospheric Emissions: Monitoring of Pollution (TEMPO) instrument is
hosted on a commercial geostationary satellite at 91°W longitude. TEMPO is an
imaging spectrometer covering Greater North America (CONUS and parts of Canada,
Mexico, and the Caribbean including Puerto Rico). The primary mission of TEMPO is
retrieval of trace-gas concentrations from the spectra of reflected sunlight. TEMPO has
an ultraviolet (290 nm – 490 nm) and a visible (540 nm – 740 nm) band with spectra
that have 0.6 nm spectral resolution and 0.2 nm spectral sampling. Direct sunlight into
or close to the aperture of TEMPO represents a potential hazard to its spectrometer. At
night, when sun safety constraints allow the aperture to be open, TEMPO can see city
lights, gas flares, maritime lights, moonlit clouds, aurorae, and nightglow without taking
time away from its primary mission. These nighttime uses had not been envisioned
when TEMPO was first proposed. This paper shows some early results from TEMPO at
night, including clearest-sky composites similar to VIIRS Day-Night Band (DNB) “Black
Marble” mosaics, classifications of city lights by their spectral signatures with radiance
by lighting type, moonlit cloud images, gas flare and wildfire pyrometry, lightning,
maritime lights, aurorae, and nightglow. Level-1 nighttime data from TEMPO are
available from the NASA Atmospheric Science Data Center (ASDC) as the “twilight”
radiance product (RADT). These data are now released in Version 4. They require no
post-processing and are easier to use than Version 3. The Version 4 RADT products
contain background-subtracted radiances that are registered to VIIRS-DNB and include
collocated DNB radiances.
How to cite: Carr, J., Chong, H., Liu, X., Houck, J. C., Kalb, V., Wang, Z., Madani, H., Lindsey, D. T., Miller, S. D., Marchenko, S. V., Xue, Z., Wang, J., Wu, D. L., Flittner, D. E., and Chance, K.: TEMPO at Night, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-22766, https://doi.org/10.5194/egusphere-egu26-22766, 2026.
Since the launch of the Geostationary Environment Monitoring Spectrometer (GEMS) in 2020, the Level-2 (L2) algorithms for atmospheric pollutant retrievals—such as nitrogen dioxide (NO₂), ozone, and aerosols—as well as for the generation of a priori data, including cloud and surface reflectance products, have been continuously improved on an annual basis. Through successive algorithm updates, the GEMS NO₂ product has shown reduced overestimation and improved representation of the stratospheric contribution, while the formaldehyde (HCHO) product has mitigated the excessive influence of chemical transport model (CTM) a priori information on the retrieval results. This study presents the major updates and changes implemented in key GEMS L2 products over the past five years and evaluates their impacts through comparisons with other satellite observations and ground-based remote-sensing measurements. These results provide a comprehensive overview of the evolution of the GEMS L2 algorithms and demonstrate their applicability for long-term air-quality monitoring.
How to cite: shin, S., lee, W., hong, H., and shin, H.: Evolution of GEMS Level-2 Algorithms for Atmospheric Composition Retrievals and Their Impacts on Air Quality Monitoring, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-6199, https://doi.org/10.5194/egusphere-egu26-6199, 2026.
Aerosol absorption (scattering) property is a key parameter for assessing aerosol radiative effects and identifying aerosol composition. However, current geostationary Earth orbit (GEO) satellite aerosol retrieval algorithms lack accuracy in estimating aerosol absorption. The Geostationary Environment Monitoring Spectrometer (GEMS) provides hyperspectral observations of Earth-reflected solar radiation from 300 nm to 500 nm, which is sensitive to aerosol absorption. However, the current aerosol retrieval algorithm for GEMS struggles to quantify aerosol loading and aerosol absorption simultaneously. Meanwhile, the Advanced Meteorological Imager (AMI) conducts band observations of Earth-reflected solar radiation from 470 nm to 1,330 nm. The longer visible wavelength bands of AMI are less sensitive to assumption errors related to aerosol absorption properties. As a result, aerosol optical depth (AOD) products retrieved from AMI are generally more stable than those from GEMS. Therefore, synergistic use of the GEMS and the AMI can be more effective than using a single instrument to obtain both aerosol loading and absorption data. Furthermore, a wide range of wavelength from UV to visible is covered by using both GEMS and AMI. This study presents sensitivity analyses and preliminary results of a synergistic retrieval algorithm for aerosol spectral absorption properties using synergistic observations from GEMS and AMI. The algorithm incorporates a Transformer-based deep learning model for radiative transfer (RT) calculations. By replacing the traditional line-by-line RT code with a deep learning model, the algorithm enables real-time RT calculations embedded within the retrieval process. This online RT calculation approach enhances the flexibility of the aerosol retrieval algorithm and reduces errors that arise from look-up table interpolation. The developed algorithm can work on other GEO-ring missions such as GeoXO, TEMPO, ABI, Sentinel-4, and FCI.
How to cite: Kim, M., Kim, J., Go, S., Cho, Y., Kim, M., Chong, H., Cha, H., Chai, Y., and Park, S. S.: A Synergistic GEO Satellite Algorithm for UV–VIS Spectral Aerosol Absorption Retrieval, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-8558, https://doi.org/10.5194/egusphere-egu26-8558, 2026.
Satellite remote sensing has played a key role in understanding distribution and changes of atmospheric composition including aerosols, ozone, air pollutants, and greenhouse gases. These contributions have been achieved extensively with Low Earth Orbit (LEO) satellite instruments providing one to two observations per day, including but not limited to MODIS, VIIRS, OMI, TROPOMI, GAOFEN, and so on.
Geostationary Environment Monitoring Spectrometer (GEMS) was launched in February, 2020 as the first component of GEO-Ring for atmospheric composition observation from geostationary Earth orbit. GEMS observation is complemented by AMI and GOCI-2 on the same spacecraft for aerosols, and hyperspectral instruments such as Chinese GIIRS. NASA’s TEMPO was launched in 2023 over North America and ESA’s Sentinel 4 UVN was launched in 2025 over Europe, to establish the GEO ring of Air Quality observation. GEMS has provided hourly observation of key air quality components, including aerosol, ozone, and their precursors such as NO2, HCHO, SO2 etc. In this talk, achievements of GEMS observations to monitor atmospheric composition of aerosol and gases from GEMS are presented with algorithm updates and validation results. Achievements and related issues with GEMS observations are discussed for further improvements and harmonization of dataset for the GEO-RING.
How to cite: Kim, J., Shin, H.-J., Ahn, M. H., Park, R., Lee, H., Kim, J.-H., Choi, Y.-S., Han, K. S., Song, C.-K., Kim, S.-W., Lee, D., Lee, W.-J., Hong, H., Kim, Y., Moon, K.-J., Ko, D. H., Lee, S.-H., Kim, M., Chai, Y., and Zeng, Z.-C. and the GEMS science Team: 5-year Operation of Geostationary Environmental Monitoring Spectrometer (GEMS) for Atmospheric Composition Observation in Asia in High Spatio-temporal Resolution, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-15783, https://doi.org/10.5194/egusphere-egu26-15783, 2026.
The recent launches of Sentinel-4 on MTG-S and Sentinel-5 on EPS-SG-A1 significantly strengthen the Copernicus contribution to the international constellation of low-Earth orbiting (LEO) and geostationary (GEO) satellites dedicated to atmospheric ozone and air quality monitoring. Together with the already operational Sentinel-5P LEO and GEMS (East Asia) and TEMPO (North America) GEO missions, these nadir sounders form an unprecedented observing system coordinated to ensure complementary spatial and temporal sampling and long-term commitment. As a prerequisite to a truly integrated exploitation of this constellation, the present contribution reports on two complementary ozone data validation activities undertaken to build confidence in their traceability to community-agreed standards and in the mutual consistency across missions.
As a first step, we summarize the global, in-depth, and recurrent validation of Sentinel-5P TROPOMI total ozone column data, conducted by the ESA/Copernicus Atmospheric Mission Performance Cluster (ATM-MPC). The ATM-MPC validation service assesses TROPOMI’s traceability to the well-established ground-based Brewer, Dobson, and ZSL-DOAS measurements contributing to WMO’s Global Atmosphere Watch (GAW) and the Network for the Detection of Atmospheric Composition Change (NDACC), and to measurements from the more recent Pandonia Global Network (PGN). The permanent QA/QC of TROPOMI demonstrates the value of this mission as the initial reference sounder for the constellation. As a second step, we present pioneering regional validation and evaluation results for the GEO missions GEMS and TEMPO performed within ESA’s PEGASOS project. This latter activity integrates independent ground-based validation and the use of TROPOMI data as a LEO transfer standard for cross-mission consistency assessment.
The ATM-MPC results confirm the high quality of TROPOMI total ozone observations, characterized by low bias, small random uncertainty, and temporal stability meeting community requirements, both with respect to ground-based reference measurements and relative to the historical benchmark provided by the Aura OMI mission. Building on these resources – both the ground-based validation infrastructure and TROPOMI as well characterized and accurate measurement system- we assess the quality of the total ozone products from GEMS and TEMPO. The analysis demonstrates overall good data quality across both GEO missions, while also identifying dependences of bias and dispersion on measurement parameters and influence quantities. These findings highlight specific areas where further algorithm refinements may enhance consistency and performance within the emerging global GEO–LEO ozone observing system.
We would like to acknowledge explicitly the long-term dedication of all the ground-based instrument teams (WMO-GAW, NDACC, PGN) to acquire high quality data and make them available to the satellite community.
How to cite: Verhoelst, T., Garane, K., Heue, K.-P., Balis, D., Compernolle, S., Keppens, A., Lambert, J.-C., Lee, H., Liu, X., Loyola, D., Lutz, R., Park, J., van Gent, J., Alparone, M., Dehn, A., Hummel, T., and Zehner, C.: Total ozone from LEO and GEO: ground-based validation and mutual consistency, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-17200, https://doi.org/10.5194/egusphere-egu26-17200, 2026.
Biomass burning (BB) significantly disturbs ecosystems and threatens regional and global climate, air quality, and human health through the massive emission of pollutants. Carbon monoxide (CO) and nitrogen dioxide (NO2) generated from these fires are key components in atmospheric chemistry, revealing combustion processes and efficiency. Over the past two decades, low-Earth-orbit (LEO) platforms have played a dominant role in trace gas monitoring; however, their snapshot sampling capabilities are unable to capture the rapid diurnal evolution of fire emissions, leading to systematic uncertainties in emission inventories. In this study, we integrate observations from the Geostationary Interferometric Infrared Sounder (GIIRS) onboard FY-4B and the Geostationary Environment Monitoring Spectrometer (GEMS) onboard GK-2B to monitor biomass burning over Southeast Asia. Validation against TROPOMI and ground-based networks (TCCON and Pandora) demonstrates the reliability of this combined dataset. Time-series analysis (July 2022–June 2025) shows that regional CO and NO2 variations exhibit high consistency with fire radiative power (FRP). Focusing on the representative fire hotspot of Northern Laos, we observe a bimodal diurnal NO2 pattern driven by the interplay of emissions, photochemistry, and meteorology. Specifically, we identified a nonlinear response of NO2 growth to fire intensity. Observational evidence suggests that under extreme burning conditions, the conversion of NOx is constrained by limited atmospheric oxidative capacity. We further quantified the intraday dynamics of combustion efficiency (indicated by the enhancement ratio, ER = ΔNO2/ΔCO), revealing significant temporal fluctuations. This pronounced diurnal variability confirms that single-overpass LEO observations introduce a systematic estimation bias in emission factors. This study provides observational constraints for refining emission inventories and demonstrates a framework for applying next-generation global geostationary satellite constellations to fire monitoring.
How to cite: Han, S., Zeng, Z.-C., Sheng, M., Kim, J., Morino, I., and Velazco, V.: Geostationary observations of air pollutants from biomass burning: a synergy of GIIRS and GEMS over Southeast Asia, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-18537, https://doi.org/10.5194/egusphere-egu26-18537, 2026.
The GEO-ring constellation of atmospheric composition missions was established to deliver continuous, diurnally resolved observations of trace gases and aerosols at regional scales. Since the launch of GK2B in 2020, the constellation has expanded to include TEMPO in 2023 and Sentinel-4 in 2025, with additional missions planned. This growing number of operating sensors emphasizes the need for cross-mission consistency and long-term radiometric stability across the GEO-ring framework.
As the first GEO-ring sensor, the Geostationary Environment Monitoring Spectrometer (GEMS) onboard GK-2B has been operating for more than five years under harsh space environmental conditions. Over this period, the optical and electronic components of the sensor have experienced degradation of up to 30%, particularly at shorter wavelengths around 300 nm. Given that this sensor has undergone the longest period of degradation, its characterization and correction provide a valuable basis for other GEO-ring sensors with similar instrumental characteristics. In this regard, this study presents post-launch calibration and evaluation methodologies for GEMS with a focus on Level 1 products, including solar irradiance and Earth reflectance. Calibration updates address long-term degradation along with angular dependence and systematic biases of the onboard solar diffuser.
For validation of the updates, GEMS is inter-calibrated with both geostationary and low Earth orbit sensors, including the Advanced Meteorological Imager (AMI) onboard the twin satellite GK2A, as well as the Tropospheric Monitoring Instrument (TROPOMI) and Ozone Mapping and Profiler Suite (OMPS). Each reference instrument provides unique strengths in spatial, spectral, and temporal coverage, enabling a comprehensive assessment of GEMS performance. The validation results indicate that the updated GEMS reflectance exhibits spectral biases within 5%, except at wavelengths below 320 nm, where straylight effects dominate.
These results demonstrate that the applied calibration and inter-calibration strategies effectively improve the radiometric consistency of GEMS Level 1 products. Building on these approaches, this work highlights the importance of in-flight calibration of Level 1 products for accurate Level 2 retrievals and long-term GEO-ring consistency.
How to cite: Lee, Y., Ahn, M.-H., Kang, M., Seo, J., Lee, J., Hong, H., Lee, C., Jeong, J., Ko, D. H., and Kim, J.: In-flight calibration and validation for Level 1 Products of GEMS, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-18679, https://doi.org/10.5194/egusphere-egu26-18679, 2026.
Formaldehyde (HCHO) is a short-lived product of volatile organic compound oxidation and a key precursor of tropospheric ozone, making it an essential proxy for surface emissions and air quality. Until recently, global HCHO monitoring relied on low-Earth-orbit (LEO) sensors, providing limited temporal coverage. The advent of geostationary UV–visible spectrometers such as GEMS, TEMPO, and Sentinel-4 now enables continuous daytime observations with high spatial and temporal resolution respectively over Asia, North America and Europe.
Within the GEO-RING project, we evaluate the GEMS operational HCHO product and explore methods to improve retrieval accuracy. Performance is assessed against ground-based networks (PGN Pandora, NDACC FTIR and MAX-DOAS) and LEO sensors (TROPOMI, GOME2-B,C), focusing on intermediate quantities such as slant columns that determine the information content from the instrument. To enhance the DOAS inversion, we test two approaches: (1) pseudo-cross-sections derived from principal component analysis of fit residuals, and (2) a CODOAS approach exploiting the covariance of the fit residuals. These methods are designed to be applicable consistently across GEMS, TEMPO, and Sentinel-4 to mitigate instrumental artifacts and scene inhomogeneity.
We also revisit background correction and air mass factor calculations for GEO observations, ensuring compatibility with LEO-based HCHO climate data records (ESA CCI). Finally, GEMS data are analysed to characterise diurnal variability over selected regions and compared with combined morning and afternoon LEO observations, demonstrating the added value of GEO sensors for future long-term atmospheric composition monitoring.
How to cite: De Smedt, I., Theys, N., Yu, H., Compernolle, S., Pinardi, G., Vigouroux, C., Lee, G., Park, R., Kim, J., and Van Roozendael, M.: Tropospheric Formaldehyde Retrievals from GEMS within the GEO-RING Project, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-21706, https://doi.org/10.5194/egusphere-egu26-21706, 2026.
Posters virtual: Tue, 5 May, 14:00–18:00 | vPoster spot 5
EGU26-23274 | Posters virtual | VPS3
First two years of TEMPO nitrogen dioxide and formaldehyde observations:algorithm status and highlightsTue, 05 May, 14:54–14:57 (CEST) vPoster spot 5
Tropospheric Emissions: Monitoring of Pollution (TEMPO) is observing air quality and
atmospheric composition over North America from a geostationary orbit since its operations
started in August 2023. TEMPO observes the continent every 40 to 60 minutes at a spatial
resolution on the order of ~ 2 x 4.5 km 2 . Together with the Geostationary Environment
Monitoring Spectrometer (GEMS, launch 2020) monitoring Asia and the Sentinel-4/UVN
(launch 2025) monitoring Europe, TEMPO is part of the current global constellation of
geostationary sensors devoted to the observation of air quality. Like GEMS and Sentinel-4/UVN,
TEMPO uses backscattered ultraviolet and visible solar radiation to retrieve atmospheric
amounts of key trace gases and aerosols associated with air quality and atmospheric chemistry.
Among the species retrieved from TEMPO observations of nitrogen dioxide and formaldehyde
are important to understand emissions and atmospheric chemistry, including the formation and
destruction of tropospheric ozone.
After multiple version updates over the first two years of the mission, the TEMPO Level 2 NO 2
and HCHO products have undergone significant enhancements to improve the performance and
accuracy of the slant column retrievals, air mass factor calculations and post-processing
corrections including destriping for NO 2 and background for HCHO. We illustrate the
performance of both retrievals (version 3 & 4), evaluating their fitting uncertainty and showing
comparisons with independent correlative measurements and other satellite products showcasing
small noise levels and remarkable accuracy with well quantified biases. We continue by
illustrating the capacity of TEMPO products focusing on different case studies showing
TEMPO’s high temporal and spatial resolution. We finalize discussing aspects of the retrieval
subject to improvement and our plans to address them.
How to cite: Gonzalez Abad, G., Nowlan, C. R., Chance, K., Liu, X., Chong, H., Fasnacht, Z., Flittner, D. E., Ghahremanloo, M., Henderson, B., Hou, W., Houck, J., Judd, L., Knowland, K. E., Shah, V., Wales, P., Qin, W., Valin, L., and Wang, H.: First two years of TEMPO nitrogen dioxide and formaldehyde observations:algorithm status and highlights, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-23274, https://doi.org/10.5194/egusphere-egu26-23274, 2026.
EGU26-23276 | ECS | Posters virtual | VPS3
The Status of the TEMPO Total-Ozone and Ozone-Profile Algorithm: V04 Updates and Comprehensive EvaluationsTue, 05 May, 14:57–15:00 (CEST) vPoster spot 5
The Tropospheric Emissions: Monitoring of Pollution (TEMPO) mission is part of a global constellation of geostationary satellites, along with GEMS and Sentinel-4, dedicated to monitoring air quality across the Northern Hemisphere. TEMPO is the first geostationary satellite instrument to monitor air pollutants over North America on an hourly basis at nearly neighborhood-scale resolution, covering an area from Mexico City to the Canadian oil sands and from the Atlantic to the Pacific Ocean.TEMPO measures backscattered ultraviolet and visible radiation to observe several trace gases important to air quality, including ozone, nitrogen dioxide, and formaldehyde, with observations every 40–60 minutes and at a high spatial resolution of approximately 2 × 4.75 km². TEMPO was successfully launched in April 2023 and began nominal operations in October 2023. Since then, it has been continuously monitoring atmospheric pollutants across its observation domain.
This presentation summarizes the Version 4 (V04) updates and improvements to the TEMPO total-ozone (O3TOT) and ozone-profile (O3PROF) retrieval algorithms. This presentation also presents the evaluation of the upcoming V04 TEMPO O3TOT product through comparisons of total ozone columns (TOCs) with measurements from other satellite instruments (e.g., OMPS and TROPOMI) and ground-based instruments, including Pandora, Brewer, and Dobson spectrometers. The V04 TEMPO O3PROF algorithm, which is UV-only, is validated through comparisons of ozone profiles, tropospheric ozone, and 0–2 km ozone columns with those from the Tropospheric Ozone Lidar Network (TOLNet) and aircraft observations, as well as through validation with MLS, EPIC, TROPOMI, and OMI observations.
How to cite: Park, J., Liu, X., Bak, J., Chong, H., Chance, K., Hou, W., Houck, J., Abad, G. G., Nowlan, C. R., Wang, H., Yang, K., Flynn, L. E., Haffner, D. P., Flittner, D. E., Knowland, K. E., Johnson, M., Demetillo, M. A. G., Spurr, R., Li, C., and Zhao, X. and the TEMPO Validation Team and NASA's GMAO Team: The Status of the TEMPO Total-Ozone and Ozone-Profile Algorithm: V04 Updates and Comprehensive Evaluations, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-23276, https://doi.org/10.5194/egusphere-egu26-23276, 2026.
