Key topics include the observation of aerosol optical properties, results from field campaigns, radiative transfer in cloud-free and cloudy atmospheres—including 3D modeling aspects—and the validation of satellite aerosol products using ground-based networks. Studies on aerosol impacts on solar radiation and energy production and aerosol assimilation into models, are also encouraged.
Particular emphasis is given to contributions from the Harmonia COST Action (AEutopean network of 150 scientists), which supports global harmonization of aerosol measurements, and the ACTRIS community, including the Calibration of Aerosol Remote Sensing (CARS) group. However, the session is open to all researchers working on aerosol measurements, modeling, and satellite product validation.
Overall, the session aims to promote collaboration and knowledge exchange to improve the quality and increase the use of aerosol data for climate, atmospheric, and solar energy applications.
Orals: Thu, 7 May, 16:15–18:00 | Room 1.85/86
Continuous observations at high spatial and temporal resolutions over the globe are necessary to characterise the high variability of atmospheric aerosol in space and time. At the global scale, two of the most widely used photometer networks for aerosol studies, operating since the end of 90’s, are SKYNET (Nakajima et al., 2020) and AERONET (AErosol ROboc NETwork; Holben et al., 1998). Both the networks provide, in near real time, day and night columnar aerosol optical and physical properties, with open access from their respective websites. The official instruments are robotic multichannel radiometers produced by PREDE and CIMEL, respectively. Both instruments measure solar (and lunar for some of them) direct irradiance and the angular distribution of sky diffuse radiation. Over the last decades, both networks have been supported by space agencies, as they represent essential tools for Fiducial Reference Measurements for satellite aerosol retrievals (e.g. Sentinel-3, TROPOMI, EarthCare). However, recent comparisons of the respective aerosol retrievals (e.g., Khatri et al., 2016; Nakajima et al., 2020; Kudo et al., 2021) revealed discrepancies in some products. This study aims to analyse common long-term datasets from both the SKYNET and AERONET instruments, at selected sites where the two instruments operate co-located: downtown Rome and Rome-Tor Vergata (Italy), Valencia (Spain), Lindenberg (Germany) and Chiba (Japan). All inversion products from simultaneous co-located measurements will be compared, and potential discrepancies will be investigated. In particular, we will focus on Single Scattering Albedo, complex Refractive Index, Asymmetry Factor, volume Size Distribution, Depolarization and Lidar Ratios, precipitable water vapour content and diurnal and nocturnal (where available) Aerosol Optical Depths (AOD). For all products, a statistical analysis of the differences will be carried out across different AOD classes using both AERONET Level 1.5 and 2.0 and SKYNET Level 2 datasets. The influence of meteorological parameters (e.g. relative humidity, wind direction and intensity, and ambient temperature) will also be evaluated. Finally, the climatology of some aerosol products from both networks will be compared.
How to cite: Campanelli, M., Kumar, G., Estelles, V., Doppler, L., Barnaba, F., Iannarelli, A., Di Bernardino, A., Irie, H., and Gomila, E.: Assessing Inversion Products Differences in co-Located SKYNET and AERONET Sites, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-4834, https://doi.org/10.5194/egusphere-egu26-4834, 2026.
Aerosol optical depth (AOD) is the single most comprehensive variable to assess the columnar aerosol load of the atmosphere. Several studies have investigated long-term AOD from ground-based observation using multiple instruments. The accuracy of AOD measurements and trends from ground-based instruments have a particular significance since they are used for satellite validation, climate model validation and modelling assimilation etc.
To ensure consistency across different networks, continuous intercomparisons are used to homogenize multi-wavelength AOD measurements. The World Optical depth Research and Calibration Center (WORCC) at PMOD/WRC operates and maintains the World Meteorological Organization (WMO) AOD reference, known as GAWPFR-TRIAD. This reference consists of three Precision Filter Radiometer (PFR) instruments. PMOD/WRC disseminates the GAWPFR-TRIAD scale through Filter Radiometer Campaigns (FRC) organized every five years on behalf of WMO. These campaigns play a crucial role in harmonizing ground-based AOD measurements globally.
The most recent Filter Radiometer Campaign (FRC) took place in September-October 2025 in Davos. This campaign brought together 33 instruments, including both filter radiometers and spectroradiometers, representing nine international and national AOD networks. The intercomparison results of spectral AOD will be presented, and the level of agreement between the networks will be assessed and compared to previous FRC campaigns (GAW Report No. 231 and 280).
An uncertainty analysis based on the information provided by each instrument will be performed and compared to the WMO traceability level of agreement, which represents calibration uncertainties of 1%. Numerous projects (e.g., ACTRIS/CARS, 19ENV04 MAPP) are focused on the optimization, standardization, and harmonization of AOD products, leading to a reduction in AOD differences to better than 0.01 at least at some wavelengths. FRC provides an opportunity to access this assumption in a global scale.
Furthermore, building on the work of the EMPIR 19ENV04 MAPP project, which focuses on AOD retrievals based on laboratory calibration of spectroradiometers (Gröbner et al., 2023) and filter radiometers (Kouremeti et al., 2022), emphasis is placed on these comparisons since the methodology has been operationally adapted by a few commercial instruments. In addition, the reference spectroradiometer QASUME is used to validate extrapolation techniques for AOD outside the spectral range of 368 nm to 863 nm covered by the GAWPFR-TRIAD reference instruments.
Acknowledgments: The authors would like to thank all the participants for the FRC-VI campaign for their contributions, time and efforts. This work was supported by GAW program of WMO and by the joint research project EMPIR 19ENV04 MAPP “Metrology for aerosol optical properties”.
References
Fourth WMO Filter Radiometer Comparison (FRC-IV), World Meteorological Organization (WMO), GAW Report No. 231, https://library.wmo.int/idurl/4/55417
Fifth WMO Filter Radiometer Comparison (FRC-V), World Meteorological Organization (WMO), GAW Report No. 280, https://library.wmo.int/idurl/4/66263
Gröbner, J., et al. (2023). Atmos. Meas. Tech., 16,4667-4680.
Kouremeti, N., et al. (2022). Metrologia, 59,044001.
How to cite: Kouremeti, N., Kazadzis, S., Gröbner, J., Hülsen, G., Karanikolas, A., Huerta, M., and Nevas, S.: Homogenization activities of ground-based aerosol optical depth measurements within WMO Filterradiometers Campaign (FRC-VI) , EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-21168, https://doi.org/10.5194/egusphere-egu26-21168, 2026.
Accurate retrieval of atmospheric carbon dioxide from ground-based solar spectral measurements in the near-infrared spectral range requires precise characterisation of interfering absorbers, such as atmospheric water vapour and aerosols. In the near-infrared spectral region, water vapour absorption strongly overlaps with carbon dioxide (CO₂) features, which is making reliable carbon dioxide retrieval highly sensitive to uncertainties in the integrated water vapour (IWV) column.
The primary objective of this work is the development of a robust CO₂ retrieval algorithm using compact spectroradiometers with moderate spectral resolution; however, as a critical prerequisite, an accurate water vapour retrieval framework must be established.
In this study, IWV is retrieved from direct solar spectral irradiance measured by a compact Bi-Tec Sensor (BTS) spectroradiometer using an optimised wavelength selection approach. The optimum wavelengths were identified through synthetic radiative transfer simulations covering a wide range of atmospheric conditions at Davos, Switzerland. Wavelengths exhibiting strong water vapour sensitivity and high stability across seasons were selected and subsequently applied to real atmospheric measurements. The resulting BTS-derived IWV algorithm was evaluated against co-located GPS IWV (AGNES) observations and compared with AERONET IWV retrievals.
The formulated BTS IWV retrieval algorithm exhibits good agreement with GPS (AGNES) measurements, with a mean bias of -1.01 mm and a standard deviation of 0.80 mm over the analysed period. In comparison, the co-located AERONET IWV retrieval shows a larger mean bias of -2.60 mm and higher residual variability of 1.82 mm, indicating the BTS-based algorithm improved stability and accuracy of water vapour retrieval. These results demonstrate that the careful selection of physically meaningful and spectrally stable wavelengths identified through synthetic radiative-transfer modelling and subsequently applied to real atmospheric measurements leads to a substantial improvement in retrieval performance.
Building on this validated water vapour retrieval, ongoing work focuses on integrating the IWV product into a CO₂ retrieval framework in the 1.6 µm to 2 µm spectral region. The established IWV retrieval provides a critical constraint for reducing systematic errors and improving the robustness of CO₂ estimation from compact spectroradiometers.
How to cite: Jaine, D. and Groebner, J.: Atmospheric trace gas retrievals and monitoring using a medium-resolution spectroradiometer , EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-6187, https://doi.org/10.5194/egusphere-egu26-6187, 2026.
The complex interactions of atmospheric aerosols with solar radiation and clouds represent a major source of uncertainty in atmospheric effective radiative forcing. These interactions are driven by aerosol optical and microphysical properties and depend critically on their spatial and vertical distribution. Consequently, obtaining accurate measurements with high spatial and temporal resolution is essential for improving climate models and reducing uncertainty. To this end, remote sensing techniques are employed globally from both space-borne and ground-based platforms. While space-borne instruments provide superior spatial and temporal coverage, ground-based techniques offer more limited spatial extent but higher measurement quality and precision.
However, both techniques measure optical quantities that depend on aerosol properties, which necessitates the use of inversion algorithms to retrieve these underlying characteristics. Among ground-based techniques, sun-sky-lunar photometers and lidars are two of the most prominent instruments, and inversion methods have been developed and applied to each separately. For instance, the AERONET inversion algorithm for photometers employs both aerosol optical depth (AOD) and sky radiance measurements at multiple viewing geometries across four wavelengths to retrieve the aerosol volume size distribution and complex refractive index. For lidars, methods as the Klett-Fernald and Raman enable the retrieval of vertically resolved aerosol properties. Nevertheless, each technique has inherent limitations: while sun photometer inversions can retrieve both optical and microphysical properties, they lack vertical resolution due to the column-integrated nature of their measurements. Conversely, lidar-based methods provide excellent vertical resolution but often rely on assumptions or ancillary data.
Consequently, the combined use of photometers and lidar systems offers the potential to provide complete and robust characterization of vertically resolved aerosol properties. To this end, numerous inversion algorithms have been developed that combine sun-sky-lunar photometers with low-power lidar systems to retrieve both columnar and vertically resolved aerosol optical and microphysical properties. This approach benefits from enhanced spatial and temporal coverage due to the widespread availability of both instrument types. Among these algorithms, GARRLiC (Now integrated into the GRASP algorithm) stands out as a flexible option capable of being applied to a wide range of photometers and lidar configurations, providing both intensive and extensive aerosol properties for two aerosol modes in the atmospheric column and with vertical resolution when the lidar system includes multiple wavelengths or polarization channels.
This study presents a synthetic evaluation of a GRASP-based inversion combining AOD and sky radiance observations (440, 675, 870, and 1020 nm) from a CE318-T sun-sky-lunar photometer with dual-wavelength elastic lidar measurements (532 and 808 nm) from a CE376 micro-pulse lidar to retrieve both columnar and vertically resolved optical and microphysical properties for two aerosol modes (fine and coarse). Our methodology involves generating synthetic observations from selected aerosol properties, adding realistic noise based on reported uncertainties, performing GRASP inversions, and comparing retrieved parameters with input values under diverse aerosol loadings and viewing geometries. This framework provides comprehensive characterization of the algorithm's performance, accuracy, and sensitivity, validating the method for operational application.
How to cite: González-Sicilia, P., Román, R., Barreto, Á., González, Y., Herrero del Barrio, C., García, R. D., Almansa, A. F., and Álvarez-Losada, Ó.: Synthetic Validation of a GRASP Inversion Strategy Combining CE376 Lidar and CE318-T Photometer Measurements, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-4897, https://doi.org/10.5194/egusphere-egu26-4897, 2026.
Photometric measurement parameters such as Single Scattering Albedo (SSA), Aerosol Optical Depth (AOD), and Angstrom Exponent (AE) can be used for aerosol classification and source identification using artificial intelligence mechanisms or simplified classification trees. Sometimes these methods are difficult to apply in incomplete datasets or when using vaguely defined classification algorithms that provide ambiguous responses about their origin. In such cases, the origin of atmospheric aerosols may be identified using air-mass trajectory models of atmospheric pollution. This study uses a NOAA HYSPLIT model, which, in addition to atmospheric photometric properties, significantly improves the analysis of results in discutable situations and may, by its nature, even replace the measurement of aerosol chemical composition when profiling sources is performed. The experimental part was developed using the AERONET dataset for Lampedusa (Italy) for the period 2020-2024.
How to cite: Steinberga, I. and Kupca, V.: Complementary air mass analysis and aerosol classification for improved source apportionment, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-18648, https://doi.org/10.5194/egusphere-egu26-18648, 2026.
Atmospheric aerosols play a crucial role in the Earth system by influencing climate, air quality, human health and environmental processes. Aerosol loading is quantified in optical terms using Aerosol Optical Depth (AOD), a wavelength dependent measure of the attenuation of solar radiation by particles in the atmosphere. The Copernicus Atmosphere Monitoring Service (CAMS) provides global aerosol reanalyses by combining numerical modelling with satellite observations (among others) via data assimilation. In the CAMS ECMWF Atmospheric Composition Reanalysis 4 (EAC4), satellite-retrieved AOD at 550 nm is assimilated to constrain aerosol fields. A parallel control simulation (CTRL), produced without AOD assimilation, enables the direct impact of assimilation to be isolated. In this study, we assess the impact of data assimilation both in the representation of the aerosol burden and its long-term variability by comparing EAC4 and CTRL configurations over the period 2003–2024. The assimilated observations in EAC4 include AOD from MODIS aboard the Terra and Aqua satellites, complemented by AATSR on-board Envisat satellite. The AOD products from both configurations are evaluated against reference ground-based AERONET measurements at 178 stations worldwide, selected after applying a set of criteria in order to ensure a robust and internally consistent analysis of long-term AOD trends. Overall, both EAC4 and CTRL show good agreement with AERONET at low AOD values (AOD < 0.2), which account for the majority of observations. However, as aerosol loading increases, both configurations tend to underestimate the actual AOD, with substantially larger biases in CTRL. Assimilation in EAC4 systematically reduces these underestimations across all AOD ranges and results in a narrower error distribution, indicating improved stability and consistency. Evaluation metrics confirm this improvement, with EAC4 exhibiting higher correlations, lower errors, and a near-zero mean bias relative to AERONET. The assimilation of satellite AOD indirectly alters the simulated aerosol composition, with the most pronounced changes occurring over dust-dominated regions, where the relative dust contribution is substantially reduced and partially redistributed toward organic matter and other aerosol components, indicating that CTRL overestimates dust loading. Additionally, satellite AOD assimilation significantly improves the representation of long-term AOD trends. Trends derived from EAC4 show strong agreement with AERONET, correctly capturing both the magnitude and sign of observed changes over the majority of the AERONET stations. Compared to CTRL, EAC4 demonstrates markedly higher correlations, reduced trend errors, and a greater fraction of statistically significant trends consistent with observations. These results highlight that satellite AOD assimilation not only enhances present-day aerosol distributions but also plays a key role in constraining long-term aerosol variability in reanalysis products.
Acknowledgements: Part of this work was supported by the COST Action Harmonia (CA21119) supported by COST (European Cooperation in Science and Technology). This work received financial support through the ACTRIS Switzerland 2025-2028 grant (Swiss contribution to the ACTRIS ERIC) funded by the Swiss State Secretariat for Education and Research and Innovation (SERI).
How to cite: Moustaka, A., Gkikas, A., Logothetis, S.-A., Flemming, J., Rémy, S., Ades, M., Tourpali, K., Amiridis, V., and Kazadzis, S.: Impact of Satellite Aerosol Assimilation on AOD Representation and Long-Term Trends in CAMS Reanalysis, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-12278, https://doi.org/10.5194/egusphere-egu26-12278, 2026.
Aerosol radiative forcing remains one of the largest sources of uncertainty in climate projections, despite substantial advances in aerosol and cloud observations from ground-based networks and satellites. We quantify how effectively current aerosol, cloud, and radiative observations constrain aerosol forcing uncertainty in global climate models, and identify where and why significant uncertainty persists. Using large perturbed-parameter ensembles of an Earth system model evaluated against satellite-derived aerosol, cloud, and radiation products, we map the spatial distribution of aerosol forcing uncertainty before and after observational constraint.
We show that observational constraints reduce aerosol forcing uncertainty by more than 70–80% in Northern Hemisphere marine regions and substantially narrow the global mean forcing range. However, large uncertainties remain in key regions, notably Southern Hemisphere stratocumulus-to-cumulus transition zones and some industrialized continental areas. Analysis of uncertainty clusters reveals common controlling processes that resist constraint even when multiple observational datasets are applied.
A central outcome of this work is that applying observational constraints to large perturbed-parameter ensembles provides new insights into structural model behaviour. Simultaneous evaluation against multiple observed aerosol and cloud properties reveals where model tuning is by necessity a compromise. This approach exposes structural model deficiencies – model development priorities.
Our results provide actionable guidance for aerosol measurement communities, including ACTRIS and Harmonia, by identifying regions and processes where improved, harmonized aerosol and cloud observations could most effectively reduce aerosol-cloud radiative forcing uncertainty. The study underscores the need for coordinated observation-model development strategies to maximize the value of long-term aerosol datasets.
How to cite: Regayre, L., Prevost, L., Ghosh, K., Johnson, J., Oakley, J., Owen, J., Webb, I., and Carslaw, K.: What aerosol and cloud observations reveal about model robustness and aerosol forcing uncertainty, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-12597, https://doi.org/10.5194/egusphere-egu26-12597, 2026.
This study aims to quantify how different stratospheric aerosol injection (SAI) scenarios influence clear-sky (cloudless) surface solar radiation (SSR) by applying benchmark radiative transfer calculations. SAI is a solar radiation modification (SRM) method, which is increasingly viewed as a potential backstop against global warming. If SRM techniques are implemented in the future, it will be important to understand their potential financial and societal implications, particularly with respect to reduced solar energy production. Currently, there is limited understanding of how SRM might influence photovoltaic (PV) power generation or which measures could effectively counteract potential declines in SSR.
We obtain SSR estimates of a reference and SAI scenarios using the libRadtran radiative transfer model [1, 2]. The SAI scenarios include an aerosol layer of different solid and liquid materials, including sulfuric acid, diamonds, alumina, and calcite aerosol particles. The optical properties of these particles were determined with the Mie scattering module in libRadtran, using the physical parameters reported in Vattioni et al., 2024 [3] and Hummel et al., 1988 [4]. We performed radiation simulations using location-specific ambient tropospheric composition profiles obtained from the Copernicus Atmosphere Monitoring Service (CAMS). We calculated it for a reference and specified SAI scenarios and for different solar PV geometries (azimuthal orientation and tilting angles).
In summary, the results reveal a slight negative percentage difference (3-12%) for low solar zenith angles (sza < 60°) of the direct horizontal irradiance component when applying an aerosol optical depth of 0.07 for all SAI scenarios. Interestingly, the differences are larger for solid particles (e.g., diamond) and increase further at higher sza values. On average, the diffuse fraction of the irradiance is about 40% higher with an SAI layer than in the reference case, increasing from roughly 110 Wm−2 to 150 Wm−2. The data will be supplied for PV energy production simulations as a function of the PV material, and the resulting outputs will offer valuable insight into how SAI could alter the Earth’s radiation budget.
This work was supported by ESA as part of the 'STATISTICS' project.
(1) Mayer, B.; Kylling, A. Atmospheric Chemistry and Physics 2005, 5, 1855–1877.
(2) Emde, C.; Buras-Schnell, R.; Kylling, A.; Mayer, B.; Gasteiger, J.; Hamann, U.; Kylling, J.; Richter, B.; Pause, C.; Dowling, T.; Bugliaro, L. Geoscientific Model Development 2016, 9, 1647–1672.
(3) Vattioni, S.; Käslin, S. K.; Dykema, J. A.; Beiping, L.; Sukhodolov, T.; Sedlacek, J.; Keutsch, F. N.; Peter, T.; Chiodo, G. Geophysical Research Letters 2024, 51, DOI: 10.1029/2024GL110575.
(4) Hummel, J. R.; Shettle, E. P.; Longtin, D. R. A New Background Stratospheric Aerosol Model for Use in Atmospheric Radiation Models; tech. rep.; OptiMetrics, Inc., 1988.
How to cite: Kilchhofer, K., Papachristopoulou, K., Geurts, M., Sukhodolov, T., and Kazadzis, S.: Effect of stratospheric aerosol injection scenarios on surface irradiation and solar energy production, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-3052, https://doi.org/10.5194/egusphere-egu26-3052, 2026.
Saharan dust outbreaks are increasingly affecting Europe, yet their impact on photovoltaic (PV) energy production is still predominantly interpreted through the lens of direct aerosol radiative attenuation. This study demonstrates that such an approach substantially underestimates the other influence of dust on solar energy generation, as the dominant mechanism operates indirectly through dust-induced modifications of cirrus clouds.
We analyse six years (2019-2024) of national-scale PV generation data from Hungary, a Central European country where solar power accounted for approximately 25% of total electricity generation by 2024. PV production data are combined with reanalysis- and satellite-based atmospheric datasets, including dust column mass density from MERRA-2, cirrus cloud properties from MODIS, and surface irradiance from the CAMS Radiation Service. PV performance is quantified using a dynamically fitted production envelope, allowing generation losses to be assessed independently of capacity growth and seasonal variability.
Our results reveal that the largest PV yield reductions occur not during high-dust conditions alone, but when elevated dust loads coincide with enhanced cirrus cloud coverage and reflectance. Under such combined conditions, PV performance ratios fall to approximately 46%, compared to values exceeding 75% during low-dust, low-cirrus periods. During high-dust episodes, cirrus reflectance increases by about 55%, while cirrus coverage rises by 60-85%, providing clear observational evidence of strong aerosol-cloud interactions. Seasonal analysis shows that these indirect effects peak during the transitional seasons (spring and autumn), when thermodynamic conditions favour heterogeneous ice nucleation on mineral dust particles.
To disentangle direct and indirect pathways, we apply both linear and non-linear (quadratic) mediation frameworks, supported by block bootstrap resampling to ensure robust statistical inference. The bootstrap analysis consistently demonstrates that the indirect, cirrus-mediated pathway is statistically significant and more stable than the direct dust effect. While direct aerosol extinction can be strong during extreme dust events, its influence is episodic and highly state-dependent. In contrast, dust-induced cirrus enhancement represents a persistent and dominant mechanism governing PV efficiency losses across dust regimes.
These findings indicate that the radiative impact of Saharan dust on solar energy production is fundamentally a coupled dust-cirrus phenomenon rather than a simple aerosol-extinction problem. As the frequency and intensity of transcontinental dust intrusions are projected to increase under future climate conditions, explicitly accounting for aerosol-cloud interactions is essential for reliable PV performance assessment, energy planning, and the stability of increasingly solar-dominated power systems.
The research was supported by the Sustainable Development and Technologies National Programme of the Hungarian Academy of Sciences (FFT NP FTA) and NRDI projects TKP2021-NKTA-21 and RRF-2.3.1-21-2021.
How to cite: Varga, G., Gresina, F., Gelencsér, A., Csávics, A., and Rostási, Á.: Beyond aerosol extinction: dominant indirect effects of Saharan dust on photovoltaic energy production in Central Europe, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-17282, https://doi.org/10.5194/egusphere-egu26-17282, 2026.
The Eastern Mediterranean and Middle East (EMME) region constitutes a critical domain for assessing the impact of atmospheric aerosols on solar photovoltaic (PV) power potential. The EMME region is characterized by exceptionally high solar resource availability and is affected by a variety of aerosol species transported from distant sources, while also hosting suspended particles of both anthropogenic and natural origin that are frequently recorded at high concentrations. Moreover, the Eastern Mediterranean, it is identified as a climate change hotspot, where projected changes in aerosol concentrations are expected to play a pivotal role. In this study, we analyze projections from the GFDL-ESM4 global climate model, participating in the 6th phase of the Coupled Model Intercomparison Project (CMIP6), to quantify the impact of aerosols’ and cloudiness’ spatiotemporal variability on PV power production in the EMME region, within the 21st century. To address this, we investigate trends and variability of radiation-related parameters – surface downwelling solar irradiance under all-sky and clear-sky conditions, under different Share Socioeconomic Pathways (SSP–based scenarios): SSP2-4.5, SSP3-7.0, SSP5-8.5. To simulate the PV power output, we employ the Global Solar Energy Estimator (GSEE), which incorporates a climate interface submodule designed to process gridded climate datasets with varying temporal resolutions, ranging from hourly to seasonal, as model input. Attenuation by cloudiness plays a significant role regarding future energy production, especially at the northernmost EMME regions. Nevertheless, the role of atmospheric aerosols is dominant during the sunniest months of the year, especially in the southeastern Mediterranean.
How to cite: Papadimitriou, N., Fountoulakis, I., Douvis, K., Misios, S., Gkikas, A., Kazadzis, S., Kazantzidis, A., and Zerefos, C. S.: Projections of PV energy production in the Eastern Mediterranean and Middle East during the 21st century: Assessing the role of atmospheric aerosols, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-830, https://doi.org/10.5194/egusphere-egu26-830, 2026.
Posters on site: Thu, 7 May, 14:00–15:45 | Hall X5
Solar Ultraviolet (UV) radiation plays a key role in many chemical and biological processes, and affects significantly human health. Excessive UV exposure may lead to adverse health effects, including sunburns, skin cancer, and cataracts, whereas moderate exposure is beneficial, e.g., by supporting vitamin D production and promoting mental well-being, among other benefits. UV radiation interacts with various atmospheric components before reaching the Earth’s surface. Photons with shorter wavelengths are absorbed at higher atmospheric layers by oxygen and tropospheric ozone, and practically only UV-A and a small part of the UV-B irradiance reach the troposphere. In the troposphere, UV is scattered by air molecules and is further attenuated by aerosols and clouds. Interactions between UV radiation and aerosols are not yet completely understood, and their parameterization constitutes a major uncertainty factor in models and satellite retrieval algorithms. Understanding these interactions is thus essential for accurately assessing UV exposure using modeled UV irradiance.
Τhe purpose of this study is to evaluate satellite- and reanalysis-based retrievals of the effective dose for the cutaneous vitamin D synthesis using ground-based measurements over Athens and Thessaloniki, Greece. We evaluate data that are derived (1) using the methodology described in Fragkos et al., (2024, https://doi.org/10.3390/rs16111878), based on CAMS information in combination with satellite data from OMI and MSG, and (2) the UV climatology of which is also based on data from various sensors analyzing air quality. Ground-based spectral solar UV irradiance measurements performed with a MKIV single monochromator Brewer spectrophotometer in Athens, and a MKIII double monochromator Brewer spectrophotometer in Thessaloniki are used to validate the Satellite-based retrievals. AOD measurements from co-located CIMEL sun-photometers, part of the AERONET network are used to assess the effect of aerosols. The evaluation has been performed for the period 2004 - 2024. Further analysis yielded positive trends in the effective dose for vitamin D production in the last two decades, mainly due the decreasing trends in aerosols.
How to cite: Stavraka, T., Fountoulakis, I., Eleftheratos, K., Nastos, P., Papazoi, T., Fragkos, K., Bais, A., Garane, K., Kazantzidis, A., Papayannis, A., Amiridis, V., and Zerefos, C.: Assessing aerosol-related uncertainties in satellite-based retrievals of effective UV doses for the production of cutaneous vitamin D. , EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-864, https://doi.org/10.5194/egusphere-egu26-864, 2026.
Accurate calibration of the Sun-sky radiometers is essential for the reliable retrieval of the aerosol optical properties. The standard Langley plot (Shaw, 1983) method is widely used to calibrate Sun-sky radiometers. Although it provides us with the most reliable calibration, the instrument has to be transported to a pristine location at high altitude to perform this procedure. An improved Langley method (ILP) was proposed by Nakajima et al. (1996) and Campanelli et al. (2004) to address this issue. Currently, ILP is widely used for PREDE POM radiometers in the SKYNET. In ILP, the Sun-sky radiometer can be calibrated on site without requiring transport to high altitude. Radiance data in the almucantar plane is used to obtain the AOD using Skyrad 4.2 (Nakajima et al., 1996). Later, this AOD is used to calculate the calibration value. Because the AOD is allowed to vary, unlike the Standard Langley plot method, which assumes AOD is constant, the calibration can be obtained even at non-ideal sites.
In this study, we upgrade the Improved Langley plot (method) by replacing the old Skyrad 4.2 inversion algorithm with the latest Skyrad MRI v2 (Kudo et al., 2021). Skyrad MRI v2 employs an optimisation of the inversion technique similar to the one used by the AERONET network. It also employs a dynamic cost function rather than the static cost function used in Skyrad 4.2. Moreover, it can handle non-spherical particles. Overall, Skyrad MRI v2 helps ILP obtain a more accurate AOD, enabling a better estimate of the calibration constant. We also propose a modification to the ILP method that uses an iterative method to calculate the calibration value. We used the data from the QUAlity and TRaciability of Atmospheric aerosol Measurements (QUATRAM, www.euroskyrad.net/quatram) campaigns and from the Skynet sites of Burjassot and Valencia, and showed that the upgraded ILP method using the iterative method improved the calibration values. The comparison of the direct AOD computed using the new calibration with co-located AERONET and PFR measurements showed an increase in the number of points in agreement within the WMO limits imposed for AOD. The mean difference in direct AOD is also reduced to within ±0.01, indicating improved consistency. The improvement was significant for wavelengths below 500 nm, whereas it was minor for wavelengths at or above 500 nm. This indicates the robustness of the ILP at longer wavelengths. At the same time, this highlights the need for a more robust approach at shorter wavelengths, which is addressed by the proposed methodology.
Acknowledgement
The current analysis has been done in the frame of the COST Action CA21119 HARMONIA, supported by COST (European Cooperation in Science and Technology). The Spanish Ministry of Economy and Competitiveness also funded the research through project PID2022-138730OB-I00. The participation of G. Kumar has been supported by the Santiago Grisolia program fellowship GRI-SOLIAP/2021/048. We thank AERONET, PHOTONS and SKYNET for their scientific and technical support
How to cite: Kumar, G., Momoi, M., Campanelli, M., Garcia-Suñer, M., Estellés, V., and Kudo, R.: Evaluation and advancement of the SKYNET Improved Langley Plot method in the Mediterranean area, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-6742, https://doi.org/10.5194/egusphere-egu26-6742, 2026.
This work presents preliminary results of the validation of ESA EarthCARE (EC) Level-2 aerosol products using ground-based observations in Rome–Tor Vergata (Italy), where a suite of instruments continuously measures aerosols, clouds, gases, and precipitation. The study is carried out within the EC-VALMED.it project funded by the Italian Space Agency (ASI), aiming to assess the accuracy of EC aerosol, cloud, and precipitation products over the Mediterranean. Here, we focus on aerosol columnar properties comparing EC satellite products with observations from ground-based photometers (AERONET and SKYNET) complemented by vertical profiles from high- and low-power lidar measurements operating within ACTRIS and ALICENET/E-PROFILE.
Satellite validation is challenging due to differences in observation geometry, mismatches in spatial and temporal resolution, and high spatiotemporal variability of aerosol optical properties. To address these issues, we defined specific match-up criteria between satellite and ground-based measurements. For EC MSI (Multi Spectral Imager) Aerosol Optical Thickness (AOT), spatial averages over 3×3, 9×9, 25×25, and 51×51 pixel areas around the Rome-Tor Vergata observatory were computed. For EC ATLID (Atmospheric Lidar), both AOT and vertical profiles were averaged over different temporal windows (i.e., along-track path-length), centered at the time of minimum distance between the satellite ground track and the Rome-Tor Vergata observatory. Only ATLID overpasses within 100 km and MSI-AOT overpasses within 150 km of the station were considered. Ground-based photometer data were also temporally averaged over different intervals, and only high-quality satellite retrievals (status 0/1) were retained.
First results indicate a good agreement between EC-ATLID AOT at 355 nm and 15-min averaged AERONET/SKYNET data at 340 nm (R = 0.86), with the best match obtained using ATLID 20-s averages. MSI-AOT shows a lower correlation at 670 nm (R = 0.65), though improvements were observed moving from EC product baseline BA to BB. In specific cases, reasons for satellite-photometers disagreements are disclosed based on vertical profiles.
This work is supported by the Italian Space Agency (ASI, ECVALMED project, agreement n. 2024-1-HB.0).
How to cite: Sensi, S., Adirosi, E., Angeloni, S., Baldini, L., Barnaba, F., Bracci, A., Campanelli, M., Casasanta, G., Dionisi, D., Di Palantonio, M., Giuliano, G., Liberti, G. L., Masi, L., and Picchiani, M.: Validation of L2 EarthCARE Aerosol Products with co-located SKYNET and AERONET photometers observation complemented by lidar profilers at the Rome Tor Vergata atmospheric observatory (Italy) , EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-18785, https://doi.org/10.5194/egusphere-egu26-18785, 2026.
Ensuring reliable and comparable aerosol optical data across monitoring networks demands automated, standardized quality control (QC) procedures. We present an integrated, real‑time QC system for AE33 Aethalometer equivalent black carbon (eBC) and Aurora 4000 nephelometer scattering coefficient (σsca) measurements. Built on the open-source SaQC framework and distributed through the actris_qc package, the system operationalizes community QA/QC guidelines through a structured, machine-readable rule hierarchy that performs device-control, channel-level, and derived-variable diagnostics. The workflow is configured using an anomaly catalogue from the urban TROPOS site and validated at the contrasting rural Melpitz station, confirming robust adaptability across diverse environments. It consistently detects outliers, noise, plateaus and instrument failures while preserving plausible atmospheric variability, reaching real-time execution on standard computing platforms. Its modular and declarative architecture facilitates seamless extension to further instruments and network infrastructures, enabling harmonized QC flagging, traceable provenance, and FAIR‑compliant, AI‑ready data streams for next‑generation atmospheric monitoring systems.
How to cite: Bumberger, J., Müller, T., Lünenschloss, P., Voigtländer, J., Trabert, T., Vosgerau, E., Schäfer, D., and Houben, T.: Automated quality control of atmospheric aerosol time series in near real-time, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-16395, https://doi.org/10.5194/egusphere-egu26-16395, 2026.
High-altitude observatories play a key role in monitoring background atmospheric composition and radiation, yet they are increasingly affected by extreme wildfire plumes. In August 2023, an intense wildfire on Tenerife (Canary Islands, Spain) reached the immediate surroundings of the Izaña Observatory, creating an exceptional near-source observational configuration at a high-altitude mountain site. This event provides a rare opportunity to investigate the spectral radiative effects of freshly emitted biomass-burning aerosols under extreme loading conditions in a clean-background environment. During the most intense phase of the episode, aerosol optical depth reached exceptionally high values, while the Ångström Exponent remained consistently elevated, indicating a strong dominance of fine-mode smoke particles. Spectral measurements of global, direct-normal and diffuse solar irradiance across the ultraviolet to near-infrared range reveal a strong attenuation of the direct solar component and a pronounced enhancement of diffuse radiation, particularly in the visible spectrum. Relative to clean-sky conditions, daily global irradiance experienced a substantial reduction, while direct-normal irradiance was strongly suppressed, in some cases approaching complete extinction. Surface aerosol radiative forcing and radiative forcing efficiency were quantified using radiative transfer simulations assuming pristine atmospheric conditions as reference. The resulting shortwave radiative forcing indicates intense surface cooling, largely driven by aerosol scattering processes. Maximum forcing and efficiency occurred in the visible spectral range, consistent with the optical properties of freshly emitted smoke aerosols. Despite a reduction in aerosol loading during the later stage of the event, radiative forcing efficiency remained comparable or slightly enhanced, reflecting changes in aerosol optical properties and solar geometry. Concurrent increases in particle concentrations, black carbon and trace gases confirm the direct impact of the wildfire plume on atmospheric composition at the observatory. These results demonstrate how extreme wildfire events can temporarily disrupt radiative and compositional conditions at high-altitude background sites and highlight the importance of accurately representing fine-mode smoke aerosols in radiative transfer and climate models.
How to cite: Rosa D., G., África, B., Victoria E., C. R., Pablo, G.-S., Sergio, L. L., Ayoze, Á. H., Juan José, B., Ramón, R., Fernando, A., Óscar, Á. L., Yenny, G. R., Pedro Pablo, R., and Carlos, T. G.: Spectral Radiative Effects of Extreme Wildfire Aerosols at the Izaña High-Altitude Observatory, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-4530, https://doi.org/10.5194/egusphere-egu26-4530, 2026.
A convolutional neural network (CNN) based model, named CNN-CMF, is proposed to estimate solar shortwave global horizontal irradiance (GHI) from daytime all-sky camera images by retrieving the cloud modification factor (CMF). This work explores the use of all-sky cameras as an additional observational resource for solar radiation studies. The model has been trained and tested using a total of 237,669 sky images paired with pyranometer GHI measurements from Valladolid and Izaña (Spain) and Lindenberg (Germany). A comparison between model results and pyranometer data shows a high determination coefficient (R²) of 0.99 for the test dataset. Statistical metrics show a mean bias error (MBE) of −2% and a standard deviation (SD) of 9%, indicating a slight underestimation of the model. The generalization capability of the model was examined using independent measurements from the Antarctic station of Marambio, which was not included in the training dataset. The retrieved GHI values remained a high correlation, with an R² of 0.95. The statistical metrics show at this location a small overestimation of the model GHI values (MBE ≈ 2%), increasing the uncertainty in the precision of the model (SD ≈ 26%). The model results present an improvement when daily irradiation values (GHId) are retrieved. These results show a performance of the model yielding MBE and SD values of approximately 3% and 11%, respectively, and an R² value up to 0.99.
This work was supported by the Ministerio de Ciencia e Innovación (MICINN), with the grant no. PID2024-157697OB-I00 and TED2021-131211B-I00375. Financial support of the Department of Education, Junta de Castilla y León, and FEDER Funds is acknowledged (CLU-2023-1-05). This work was funded by European Comision through the EUBURN-RISK project (INTERREG-SUDOE; S2/2.4/F0327). The authors acknowledge the support of COST Action CA21119 HARMONIA and the Spanish Ministry for Science and Innovation to ACTRIS ERIC and the Marie Sklodowska-Curie Staff Exchange Actions with the project GRASP-SYNERGY (grant no. 10 101131631).
González-Fernández, D., Román, R., Mateos, D., Herrero del Barrio, C., Cachorro, V.E., Copes, G., Sánchez, R., García, R.D., Doppler, L., Herrero-Anta, S., et al. (2024). Remote Sensing, 16, 3821.
How to cite: González-Fernández, D., Román, R., Mateos, D., Herrero del Barrio, C., Cachorro, V. E., Copes, G., Sánchez, R., García, R. D., Doppler, L., Herrero-Anta, S., Antuña-Sánchez, J. C., Barreto, Á., González, R., Gatón, J., Calle, A., Toledano, C., and de Frutos, Á.: Retrieval of Solar Shortwave Irradiance from All-Sky Camera Images, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-5430, https://doi.org/10.5194/egusphere-egu26-5430, 2026.
Ultraviolet (UV) radiation has a major impact not only on human health (e.g., vitamin D synthesis, erythema, and skin and eye diseases) but also on the Earth’s environment, influencing all living organisms and interacting chemically with various commonly used materials. For these reasons, accurately measuring UV radiation and understanding its response to atmospheric changes—its primary modulator and the medium responsible for the largest variations in the UV flux reaching the surface—are of great importance.
Aerosols, particularly mineral dust, exert significant effects on solar radiation by scattering or absorbing it, thereby contributing to atmospheric cooling or warming, respectively. Several optical properties govern these effects, including the Single Scattering Albedo (SSA), the refractive index, and the Absorption Aerosol Optical Depth (AAOD). Previous studies have shown that dust optical properties in the UV range, are linked to enhanced absorption, which is linked to the mineralogical composition of the particles. However, NASA’s Aerosol Robotic Network (AERONET), one of the main global sources of aerosol data, does not provide inversion products (such as SSA and the imaginary part of the refractive index, k) at UV wavelengths. Consequently, there remains limited knowledge regarding dust effects on UV radiation. This work therefore aims to deepen the understanding of the absorption properties of dust aerosols in the solar UV range. Knowing these properties especially in dust events that are commonly linked with moderate to high aerosol optical depth is essential for the determination of UV e.g. in UV Index forecasting models.
To achieve this objective, a multi-instrumental approach will be employed using ground-based solar radiometers located at key stations influenced by major global dust sources (namely the Sahara, the Arabian Desert, and the arid regions of Western and Central Asia).
Acknowledgements: This work is supported by the Marie Curie Doctoral Network project (GA101168425), Dust-DN and by the COST Action HARMONIA CA21119, supported by COST (European Cooperation in Science and Technology).
How to cite: Huerta Gómez, M., Bais, A., Redondas, A., Meloni, D., Fountoulakis, I., di Sarra, A., Garane, K., Kazadzis, S., and WIld, M.: Dust optical properties in the UV, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-6009, https://doi.org/10.5194/egusphere-egu26-6009, 2026.
Measuring aerosol properties such as aerosol optical depth (AOD) at nighttime is crucial for understanding the overall impact of aerosols on climate, especially during polar night. Nocturnal AOD measurements can be obtained using Moon photometers; however, the Moon is not present throughout the entire night, resulting in a lack of AOD observations during more than half of the nighttime period. Star photometers, which use different stars as targets, can fill this gap. Nevertheless, only a few star photometers are currently operating worldwide, as they are expensive instruments and present several challenges for unattended operation.
Within this framework, this study explores the use of all-sky cameras, capable of capturing images of the entire sky vault, to extract the incoming irradiance of several visible stars and use this information to retrieve nighttime AOD both under Moon presence and during Moon-free periods. A new methodology to extract star irradiances from all-sky camera images is proposed, together with a Langley-plot technique to estimate AOD from these irradiances (Román et al., 2025). The resulting AOD values were calculated at several locations and compared with Moon photometer measurements. The comparison shows a high correlation between both datasets at all sites. On average, the proposed method overestimates Moon photometer AOD values by approximately 0.02, with a precision of about 0.03–0.04.
These results indicate that all-sky cameras could provide a viable solution to fill the nighttime AOD observation gap on a global scale, owing to their low cost and fully automatic operation.
How to cite: Roman, R., Gonzalez-Fernández, D., Antuña-Sanchez, J. C., Herrero del Barrio, C., Herrero-Anta, S., Barreto, Á., Cachorro, V. E., Doppler, L., González, R., Ritter, C., Mateos, D., Kouremeti, N., Copes, G., Calle, A., Granados-Muñoz, M. J., Toledano, C., and de Frutos, Á. M.: Retrieval of nighttime AOD values with all-sky cameras, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-8253, https://doi.org/10.5194/egusphere-egu26-8253, 2026.
Large wildfire episodes can substantially perturb regional aerosol loads and atmospheric composition; however, their quantitative impact remains difficult to constrain due to uncertainties in fire emissions, plume rise, and aerosol properties. During August 2025, exceptionally intense wildfire events affected large areas of the Iberian Peninsula, leading to severe aerosol emissions, reduced visibility, and pronounced air-quality degradation over extensive regions. In this study, we investigate these events by ground-based aerosol observations from CAECENET, an automatic system that retrieves vertically-resolved and column-integrated aerosol properties by applying the GRASP (Generalized Retrieval of Atmosphere and Surface Properties) inversion algorithm to combined sun–sky photometer and ceilometer measurements (Román et al. 2018).
The atmospheric aerosol emissions are primarily characterized at several sites in Spain and Portugal, including Valladolid, Madrid, Badajoz, Évora, and Granada. This network provides continuous measurements of optical and microphysical aerosol properties, enabling detailed monitoring of aerosol optical depth (AOD), fine and coarse mode contributions, and temporal evolution during the episodes. In addition, information on aerosol vertical distribution and plume heights is analyzed to assess the altitude at which fire related aerosols were injected and transported.
Satellite based fire products from the Global Fire Assimilation System (GFAS) and surface European Monitoring and Evaluation Programme (EMEP) data are used to complement this analysis.
This study highlights the value of dense ground-based aerosol networks such as CAECENET for monitoring extreme wildfire impacts, providing essential information to complement satellite observations and models, and for the assessment of the radiative effects of fire-emitted aerosols.
This work was supported by the Ministerio de Ciencia e Innovación (MICINN), with the grant no. PID2024-157697OB-I00. This work is part of the project TED2021-131211B-I00375 funded by MCIN/AEI/10.13039/501100011033 and European Union, “NextGenerationEU”/PRTR, is based on work from COST Action CA21119 HARMONIA and the Marie Sklodowska-Curie Staff Exchange Actions with the project GRASP-SYNERGY (grant no. 10 101131631). Financial support of the Department of Education, Junta de Castilla y León, and FEDER Funds is gratefully acknowledged (Reference: CLU-2023-1-05). This work was funded by European Comision through the EUBURN-RISK project (INTERREG-SUDOE; S2/2.4/F0327). The authors acknowledge the support of the Spanish Ministry for Science and Innovation to ACTRIS ERIC.
Román, R. et al., 2018: Retrieval of aerosol profiles combining sunphotometer and ceilometer measurements in GRASP code, Atmospheric Research, 204, 161-177.
How to cite: Mateos, D., Herrero del Barrio, C., Román, R., González-Fernández, D., Herrero-Anta, S., González, R., Longarela, B., Gatón, J., Calle, A., Toledano, C., Cachorro, V., and de Frutos, A.: Extreme Aerosol Loadings from Iberian Peninsula Wildfires , EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-11157, https://doi.org/10.5194/egusphere-egu26-11157, 2026.
Quantifying variations of the aerosol load and characteristics in the Southern European Alps is crucial for distinguishing local from Po Basin and broader synoptic contributions. This work presents long-term observations from the Aosta-Saint Christophe Observatory (570 m a.s.l.), focusing on the analysis of the SKYNET Prede POM-02 dataset (operational since 2012) and its synergy with a recently installed AERONET Cimel CE318-TS9 (since 2023). We present long-term aerosol trends derived from the POM series and discuss their relationship with air quality policies and atmospheric circulation changes. Furthermore, we analyze the consistency between SKYNET and AERONET products during the overlapping period, discussing harmonization procedures in light of instrumental differences and retrieval assumptions. The ultimate aim is to derive a harmonized climatology to establish a robust baseline for the region and to support future experimental campaigns deploying distributed photometers to investigate aerosol gradients across the Alpine valley.
How to cite: Bellini, A., Desandré, C., Campanelli, M., Barreto, A., González Catón, R., Barnaba, F., and Diémoz, H.: Atmospheric aerosols in the Southern European Alps: Long-term SKYNET observations and synergy with AERONET at the Aosta–Saint-Christophe station, Italy, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-11648, https://doi.org/10.5194/egusphere-egu26-11648, 2026.
Cyprus is characterized by some of the highest ultraviolet (UV) radiation levels in Europe, emphasizing the need for accurate UV Index (UVI) forecasting to support public awareness and health protection, atmospheric research. This study presents the evaluation of the Cyprus Erythemal Irradiance Forecasting System (CERYFOS), an operational system providing hourly UVI forecasts across Cyprus at a spatial resolution of 0.1° × 0.1°.
CERYFOS is based on radiative transfer simulations using libRadtran package, driven by aerosol optical properties from the Copernicus Atmosphere Monitoring Service (CAMS), satellite-based total ozone column forecasts from TEMIS, surface elevation information, and cloud related information derived from the Weather Research and Forecasting (WRF) model forecast for clear-sky and all-sky conditions.
The evaluation covers approximately one year of data (July 2024–September 2025) and is based on comparisons with high-quality ground-based measurements in Limassol, including a Kipp & Zonen SUV-E erythemal radiometer and a double monochromator Bentham DMc150 spectrophotometer, operated following established calibration and traceability protocols. Clear-sky conditions were identified using all-sky camera observations. In addition, CERYFOS forecasts are compared with CAMS UVI products, while satellite ozone data from the Ozone Monitoring Instrument (OMI) are used to assess the consistency and impact of forecasted ozone input on UVI forecast performance. The influence of aerosol input uncertainties is investigated through comparison of CAMS aerosol optical depth with co-located AERONET observations and their effect on UVI differences.
This work underscores the value of harmonized aerosol and ozone observations and traceable ground-based UV measurements for improving UVI forecasting systems and supports ongoing Harmonia efforts in aerosol–radiation interaction studies and UV exposure services.
Acknowledgments:
The authors acknowledge the ‘EXCELSIOR’: ERATOSTHENES: Excellence Research Centre for Earth Surveillance and Space-Based Monitoring of the Environment H2020 Widespread Teaming project (www.excelsior2020.eu). The ‘EXCELSIOR’ project has received funding from the European Union’s Horizon 2020 research and innovation programme under Grant Agreement No. 857510, the Government of the Republic of Cyprus through the Directorate General for the European Programmes, Coordination and Development, and the Cyprus University of Technology. Authors would like to acknowledge the Action Harmonia CA21119 supported by COST (European Cooperation in Science and Technology). G.C., K.P., A.N., and S.K. acknowledge: “ATARRI: This project has received funding from the European Union’s Horizon Europe Twinning Call (HORIZON-WIDERA-2023-ACCESS-02) under grant agreement No. 101160258.
How to cite: Charalampous, G., Fragkos, K., Fountoulakis, I., Papachristopoulou, K., Nisantzi, A., Hadjimitsis, D., and Kazadzis, S.: Evaluation of the Cyprus UV Index (UVI) Forecasting System Over One Year of Observations: Assessing the Impact of Ozone and Aerosols , EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-14140, https://doi.org/10.5194/egusphere-egu26-14140, 2026.
The 6th Filter Radiometer Comparison campaign for Aerosol Optical Depth (AOD) measurements was held from 20th of September to 10th (extended to 17th) of October 2025 in Davos (Switzerland). This campaign was organised by the PMOD/WRC and supported by the World Meteorological Organisation. For AOD measurements, groups with sun-photometers and spectroradiometers participated, including reference instruments representing several major global networks (such as the Cimel-CE318T, belonging to AERONET; the Prede-POM 1 and 2, which are the instruments used by SKYRAD; and the Precision Filter Radiometers, PFRs, that belong to the GAWPFR network). The main objective of the campaign was the harmonisation and traceability of ground-based aerosol optical depth measurements to the WMO AOD reference scale, as maintained by the PMOD/WRC reference Precision Filter Radiometers (PFRs). Furthermore, the fact that these data are collected at the same time and place allows the discrepancies in the measurements to be attributed to the instrumentation, processing algorithms or calibration processes, providing an opportunity to understand the limitations of existing methods and suggest possible improvements. In this study, the AOD from Prede-POMs was compared to the obtained based on the Cimel-CE318T and PFR measurements. Some discrepancies were found in the 340 nm and 1020 nm channels. Prede-POM’s overestimation of AOD at 1020 nm could be related to temperature effects or calibration issues (i.e. the performance of the Improved Langley Plot method in Davos, filter degradation, etc.) and requires further investigation. Another task that was successfully carried out was the validation of the SUNRAD algorithm, which is adopted by the SKYNET network to obtain AOD, when applied to raw data from the Cimel-CE318T, showing mostly good agreement with the AOD provided by AERONET (MBD = -0.0005 and RMSD = 0.0014 for Cimel #953 and MBD = -0.0005 and RMSD = 0.0006 for Cimel #1144 for AOD at 675 nm). In addition, several analyses of the SKYNET calibration method of Prede-POMs have been performed. In particular, two versions of the calibration processing algorithm, along with some variations, have been run: the standard Improved Langley Plot (ILP), and a new version recently developed. Then, the obtained calibration coefficients were used in the computation of AOD for the Prede-POMs, which was compared to the results from AERONET and GAWPFR. This analysis confirmed that the deterioration of a filter affects the determination of the Solid View Angle (SVA), and thus the computation of the calibration coefficients. In particular, it was found that the comparisons improved when the 340 nm channel from Valencia’s Prede-POM was excluded during the computation of the calibration coefficients. However, the calculation of a new SVA using disk scan measurements collected during the campaign did not yield a significant improvement in the AOD comparison.
How to cite: Garcia-Suñer, M., Kumar, G., Estellés, V., Utrillas, M. P., Campanelli, M., Kouremeti, N., González, R., Karanikolas, A., Blarel, L., and Barreto, Á.: Analysis of SKYNET derived AOD during the FRC VI campaign in Davos, and validation of improved data processing and calibration algorithms , EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-12178, https://doi.org/10.5194/egusphere-egu26-12178, 2026.
Accurate and harmonized aerosol observations are essential for climate studies, validation of satellite products, and assessment of aerosol impacts on surface solar radiation. Low-cost hand-held sun-photometer sensors facilitate a high monitoring density, providing near-real time and spatially distributed information. Their compact design and portability make them ideal for mobile monitoring observations. They can complement global monitoring networks by enabling aerosol observations in data-sparse regions, where conventional sun-photometric observations are limited. These capabilities are particularly valuable for target field campaigns, as they enable spatially and temporally collocated aerosol observations that support the validation of satellite-derived aerosol products.
This study presents results from the RACE-ECV (Radiation closure experiments for EarthCARE Validation) field campaign conducted in Thessaloniki, Greece between 24 April and 21 May 2025. The campaign included coordinated calibration and validation activities focusing on low-cost, hand-held sun-sky photometers and the evaluation of Aerosol Optical Thickness (AOT) products from the EarthCARE mission, with particular emphasis on the EarthCARE Multi-Spectral Imager (MSI) and Atmospheric Lidar (ATLID) AOT satellite products.
Six hand-held sun-photometers, three Microtops II and three Calitoos, participated in the campaign. Measurements were performed at three locations: a central urban site of the city at the Laboratory of Atmospheric Physics (LAP) of the Aristotle University of Thessaloniki (AUTH) (40.38° N, 22.57° E, 60 m a.s.l.), an urban-suburban location at Center for Interdisciplinary Research and Innovation (KEDEK) (40.33° N, 22.59° E, 63 m a.s.l.) of AUTH and a rural location in Epanomi (40.20° N, 22.58° E, 17 m a.s.l.).
Cloud-free measurements were conducted on 17–18 May 2025 at the Laboratory of Atmospheric Physics (LAP) station of (AUTH), Greece, using these handheld sun photometers. These observations were part of a coordinated calibration exercise, where the hand-held instruments were calibrated against a reference Cimel sun–sky photometer which is regularly maintained and calibrated according to AERONET standards. New calibration factors for the instruments were also derived from AOD measurements obtained with a collocated Global Atmosphere Watch precision-filter radiometer (GAW-PFR) at the KEDEK station in multiple wavelengths.
Finally, for the validation of the EarthCARE Aerosol Optical Thickness (AOT) from MSI and ATLID, mobile observations were conducted at six locations along the EarthCARE overpass tracks on 25 April and 20 May 2025 in Thessaloniki district with Microtops II and Calitoo instruments. These measurements complemented the fixed-station observations, enhancing the spatial coverage of the campaign. Results regarding the calibration of the hand-held instruments and validation of EarthCARE AOT products will be presented.
Acknowledgements: The authors acknowledge the project RACE-ECV, (SBFI-633.4-2021-2024/PMOD - EarthCARE 202/2) supported by SBFI the CERTAINTY project funded from Horizon Europe programme under Grant Agreement No 101137680. The study is supported by the ATARRI project funded by the European Union’s Horizon Europe Twinning Call (HORIZON-WIDERA-2023-ACCESS-02) under the grant agreement No 101160258 and the ‘EXCELSIOR’: ERATOSTHENES: H2020 Widespread Teaming project. This work supported by HARMONIA COST Action CA21119 - International network for harmonization of atmospheric aerosol retrievals from ground based photometers, supported by COST (European Cooperation in Science and Technology).
How to cite: Savva, A., Kazadzis, S., Biskas, C., Charalampous, G., Papachristopoulou, K., Poutli, M., Kouklaki, D., Balis, D., Nisantzi, A., Hadjimitsis, D., and Mamouri, R.-E.: Evaluation and Intercalibration of Various Low-Cost Sun-Photometers During the RACE-EarthCARE Validation Experimental Field Campaign in Thessaloniki, Greece, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-16500, https://doi.org/10.5194/egusphere-egu26-16500, 2026.
Atmospheric aerosols influence the Earth’s energy balance through direct (aerosol-radiation) and indirect (aerosol-clouds) effects. Aerosol properties are very variable in space, time and type. An accurate knowledge of the microphysical and optical properties is key to assess their impact on climate. The sky radiances contain information about the aerosol properties and are commonly used in inversion algorithms to retrieve them, like the one from AERONET (Sinyuk et al., 2020). However, the inversion algorithms commonly used employ a RTM which only considers cloud-free conditions. Therefore, the input measurements used for the inversion algorithm are previously filtered using a cloud-screening to remove sky radiances at points where clouds are located.
However, the synthetic study conducted by Herrero-Anta et al. (2025) showed that even the points which are not removed by the cloud-screening are affected by the presence of clouds, showing an enhancement in the sky radiances with respect to the cloud-free situation. When the enhanced sky radiances are used as input for an inversion algorithm, a bias is observed in the aerosol properties with respect to the aerosol properties retrieved under cloud-free conditions.
To evaluate this effect in real conditions, a new methodology has been proposed to reconstruct clouds in 3D using images from all-sky cameras. For this study, we have used data from a camera installed in Valladolid, where a CE318-T sun photometer from AERONET is co-located.
Once the 3D cloud maps are obtained, they have been used as input for the radiative transfer model MYSTIC (Emde et al., 2016) to simulate the sky radiances under cloudy and cloud-free conditions, to calculate the enhancement. This enhancement has been used to correct the sky radiance measurements from the CE318-T and retrieve the corrected aerosol properties using GRASP (Generalized Retrieval of Atmosphere and Surface Properties; Dubovik et al., 2021).
This work was supported by Ministerio de Ciencia e Innovación (MICINN), with the grant no. PID2024-157697OB-I00. This work is part of the project TED2021-131211B-I00375 funded by MCIN/AEI/10.13039/501100011033 and European Union, “NextGenerationEU”/PRTR and is based on work from COST Action CA21119 HARMONIA. Financial support of the Department of Education, Junta de Castilla y León, and FEDER Funds is gratefully acknowledged (Reference: CLU-2023-1-05). This work was funded by European Comision through the EUBURN-RISK project (INTERREG-SUDOE; S2/2.4/F0327). The authors acknowledge support of the Spanish Ministry for Science and Innovation to ACTRIS ERIC and the Marie Sklodowska-Curie Staff Exchange Actions with the project GRASP-SYNERGY (grant no. 10101131631).
Dubovik, Oleg, et al. "A comprehensive description of multi-term LSM for applying multiple a priori constraints in problems of atmospheric remote sensing: GRASP algorithm, concept, and applications." Frontiers in Remote Sensing 2 (2021): 706851. Emde, Claudia, et al. "The libRadtran software package for radiative transfer calculations (version 2.0. 1)." Geoscientific Model Development 9.5 (2016): 1647-1672. Herrero-Anta, Sara, et al. "Impact of cloud presence on sky radiances and the retrieval of aerosol properties." Atmospheric Research 317 (2025): 107938. Sinyuk, Alexander, et al. "The AERONET Version 3 aerosol retrieval algorithm, associated uncertainties and comparisons to Version 2." Atmospheric Measurement Techniques 13.6 (2020): 3375-3411.
How to cite: Herrero Anta, S., Román, R., Gonzalez-Fernández, D., Herrero del Barrio, C., Gatón, J., Longarela, B., Mateos, D., González, R., Toledano, C., Calle, A., Cachorro, V. E., Mayer, B., and de Frutos, Á. M.: 3D cloud reconstruction from all-sky camera images for the analysis of their impact on sky radiances and retrieved aerosol properties, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-17011, https://doi.org/10.5194/egusphere-egu26-17011, 2026.
Ground-based spectral observations of solar radiation provide a powerful constraint on aerosol–radiation interactions and support the validation of satellite aerosol products. This study presents a radiative transfer modelling and inversion framework for the retrieval of aerosol optical depth (AOD) and single scattering albedo (SSA) from spectrally resolved direct normal irradiance (DNI) and global horizontal irradiance (GHI) measurements in the 300–1100 nm wavelength range.
The methodology exploits the complementary sensitivity of DNI and GHI to aerosol extinction and absorption across the measured spectral region. Forward simulations are performed using a radiative transfer model, while an optimal estimation inversion scheme is applied to retrieve aerosol optical properties by minimizing the spectral residuals between modelled and measured irradiances.
The approach is applied at two contrasting environments in Greece: a high-altitude continental background site at Kalavryta and a coastal site at Epanomi. These locations represent distinct aerosol regimes influenced by long-range transport, boundary-layer dynamics, and marine contributions. Site-specific atmospheric profiles, surface albedo, and solar geometry are explicitly accounted for in the simulations.
Independent validation is performed using co-located Sun photometer measurements providing reference AOD and SSA products. For cloud-free conditions, retrieved AOD at 500 nm shows a mean bias below 0.05 and a root-mean-square error of 0.04–0.06, depending on site and aerosol load. SSA retrievals exhibit mean deviations below 0.05 in the visible range, with increased sensitivity under moderate to high aerosol loading. The coastal site demonstrates enhanced absorption variability linked to mixed marine-continental aerosol, while the mountain site is dominated by aged continental and transported aerosol.
The results demonstrate that combined spectral DNI and GHI measurements can robustly constrain aerosol optical properties with high temporal resolution, offering a complementary ground-based observational capability for aerosol monitoring, radiative studies, and satellite validation activities.
How to cite: Kairaktidi, N., Logothetis, S.-A., Kosmopoulos, G., Ioannidis, P., Kazadzis, S., Kouremeti, N., Papayannis, A., and Kazantzidis, A.: Retrieval of Aerosol Optical Properties from Spectral Solar Irradiance Using Radiative Transfer Modelling in Mountain and Coastal Environments, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-17752, https://doi.org/10.5194/egusphere-egu26-17752, 2026.
Aerosol optical depth (AOD) describes the overall direct effect of the aerosol column direct on solar radiation, which makes it a particularly important parameter for Earth energy budget related studies. Various instrument networks measure AOD worldwide such as the Aerosol RObotic NETwork (AERONET), the Global Atmospheric Watch Precision Filter Radiometer (GAW-PFR) network (Kazadzis et al., 2018) and SKYNET.
PMOD/WRC is designated from the World Meteorological Organization (WMO) and the International Bureau of Weights and Measures to maintain the world reference AOD standards and serve as the central calibration laboratory under the WMO’s Global Atmosphere Watch Program. The reference AOD dataset is provided by three precision filter radiometers (PFR). PMOD/WRC aims at standardisation and homogenisation of AOD reference scales. Also to improve the calibration, processing algorithms and consistency of long‐term measurements. Under CARS (Calibration of Aerosol Remote Sensing) of ACTRIS, PMOD/WRC aims to establish the traceability link between the AOD measured by ACTRIS instruments to the WMO reference and thereby to the SI.
In accordance with this goal, in this work we focus on the comparison of AOD measurements from CIMEL and PFR traveling reference standards at the three ACTRIS/CARS and AERONET calibration sites:
- Izaña Observatory, Tenerife, Spain (28.3 N, 16.5 W, 2401 m above sea level). Parallel measurements at Izaña started in 2002.
- The Observatoire de Haute-Provence (43.93 N, 5.71 E, 680 m a.s.l.), France. The PFR observations started in 2020.
- The University of Valladolid, Spain (41.66 N, 4.70 W, 705m a.s.l.). PFR observations started in June of 2022.
We also assess the performance of the intercomparisons according to the WMO limits for traceability and the AOD instrument uncertainties.
Acknowledgements
This work was supported by the ACTRIS-CH (Aerosol, Clouds and Trace Gases Research Infrastructure – Swiss contribution) funded by the State Secretariat for Education, Research, and Innovation, Switzerland.
The authors acknowledge the support of the Spanish Ministry for Science and Innovation to ACTRIS ERIC.
References
Kazadzis, S., Kouremeti, N., Nyeki, S., Gröbner, J., and Wehrli, C.: The World Optical Depth Research and Calibration Center (WORCC) quality assurance and quality control of GAW-PFR AOD measurements, Geosci. Instrum. Method. Data Syst., 2018.
WMO: Aerosol Measurement Procedures, Guidelines and Recommendations, WMO No 1177, 2016.
How to cite: Karanikolas, A., Kouremeti, N., Barreto, A., Toledano, C., Goloub, P., Gröbner, J., and Kazadzis, S.: AOD long term comparisons of CIMEL and PFR measurements at the ACTRIS sun-photometer calibration sites, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-18332, https://doi.org/10.5194/egusphere-egu26-18332, 2026.
For many critical energy-related applications, such as reliable PV power production, accurate Global Horizontal Irradiance (GHI) short-term forecasts are crucial. Forecasts of GHI, as analyzed in this study, are produced by the state-of-the-art, high-resolution forecasts developed within the Destination Earth initiative, the ECMWF Digital Twin Engine using the ExtremeDT (Weather-Induced Extremes Digital Twin) dataset, that produces daily global simulations at resolutions of 4.4 km kilometres up to four days ahead. However the GHI ExtremesDT forecasts do not take into account the aerosol effects, which may introduce systematic biases, especially during periods of high aerosol load events. We investigated the impact of aerosols on DT GHI forecasts and the associated PV power predictions within the context of the DestinE Destination Renewable Energy (DRE) use case.
We analyze almost one year of data comprising two-day-ahead DT GHI forecasts and the corresponding aerosol optical depth (AOD) forecasts from the Copernicus Atmosphere Monitoring Service (CAMS). The DT GHI forecasts are corrected for aerosol effects using fast radiative transfer model techniques utilising the lidRadtran [1, 2] package.
Within the DRE project, and based on co-design activities with the project's end user, site-specific PV power production forecasts tailored to the user’s needs and infrastructure were developed, using DT GHI forecasts and a machine learning (ML) model that was trained on the user’s historical data. The impact of aerosol correction was also evaluated by comparing PV power production forecasts derived from GHI forecasts with and without aerosol correction against the actual PV power production of the plant.
A machine learning (ML) model, trained on historical, site-specific production data from the QUEST PV park, was created within the DRE project to convert predicted solar irradiance into PV park power output in order to evaluate the impact on power production. The ML model propagates the original and aerosol-corrected GHI forecasts, which are then compared to actual production.
The results show how CAMS-based aerosol correction of GHI forecasts can reduce bias and consistently improve PV power prediction. Results show the value of incorporating atmospheric composition data with ML-based power conversion models for operational energy applications, as well as the significance of aerosol representation in solar forecasting.
Acknowledgments
DRE project has received funding from the European Space Agency under the DESTINATION EARTH USE CASES – DESP USE CASES - ROUND 1. The duration of the project is 12 months (November 2023 - November 2024).
We would like also to acknowledge the COST Action HARMONIA (International network for harmonization of atmospheric aerosol retrievals from ground based photometers), CA21119.
Bibliography
(1) Mayer, B.; Kylling, A. Atmospheric Chemistry and Physics 2005, 5, 1855–1877.
(2) Emde, C.; Buras-Schnell, R.; Kylling, A.; Mayer, B.; Gasteiger, J.; Hamann, U.; Kylling, J.; Richter, B.; Pause, C.; Dowling, T.; Bugliaro, L. Geoscientific Model Development 2016, 9, 1647–1672.
How to cite: Georgakis, A., Chadoulis, R.-T., Kazadzis, S., Papachristopoulou, K., Casalieri, D., and Kontoes, C.: Assessing Aerosol Impact on Digital Twin Solar Irradiance Forecasts and on PV Power Prediction, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-20184, https://doi.org/10.5194/egusphere-egu26-20184, 2026.
Posters virtual: Tue, 5 May, 14:00–18:00 | vPoster spot 5
EGU26-3325 | ECS | Posters virtual | VPS3
Long Term Analysis of Aerosol Properties Over the Eastern Mediterranean Using Grasp Retrieved AERONET DataTue, 05 May, 15:09–15:12 (CEST) vPoster spot 5
This study presents a comprehensive climatological analysis of aerosol optical and microphysical properties over the Eastern Mediterranean, utilizing long-term AERONET measurements from Mersin/Erdemli (IMS-METU) site. The Generalized Retrieval of Aerosol and Surface Properties (GRASP) algorithm was used to retrieve key parameters, including Aerosol Optical Depth (AOD), Single Scattering Albedo (SSA), and Volume Size Distribution, offering robust separation of surface and aerosol properties.
Results revealed a distinct seasonal cycle in aerosol loading, with AOD peaking in summer (July-August) due to fine-mode pollution and exhibiting a secondary peak in spring (April) driven by mineral dust transport from desert regions. The annual mean SSA displays a negative spectral slope, decreasing from ~0.93 at 440 nm to ~0.90 at 1020 nm, indicating a background atmosphere dominated by fine-mode urban-industrial aerosols. Although winter months exhibit the lowest total aerosol load due to wet scavenging, they display the strongest absorption characteristics. The imaginary refractive index significantly exceeds 0.015, and SSA values drop sharply during winter, attributed to Black Carbon emissions from domestic heating. The volume size distribution maintains a bimodal structure year-round; while the coarse mode dominates during spring dust events, the fine mode contribution remains substantial across all seasons. The aerosol population over the Eastern Mediterranean is characterized as a heterogeneous mixture where the anthropogenic fine-mode background is periodically modulated by natural mineral dust intrusions and local carbonaceous emissions.
How to cite: Çetiner, A. S. and Aslanoğlu, S. Y.: Long Term Analysis of Aerosol Properties Over the Eastern Mediterranean Using Grasp Retrieved AERONET Data, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-3325, https://doi.org/10.5194/egusphere-egu26-3325, 2026.
EGU26-13698 | Posters virtual | VPS3
Inferring aerosol optical depth at unmeasured wavelengths from ground-based spectral photometer data: uncertainty-consistent regression, sensitivity tests, and application to real dataTue, 05 May, 15:12–15:15 (CEST) vPoster spot 5
Aerosol optical depth (τ) is routinely reported at wavelengths that are not directly measured by ground-based sun photometers, in particular at 550 nm for satellite validation and at longer wavelengths for short-wave infrared applications. These values are typically obtained by spectral interpolation or extrapolation, most often using linear or quadratic regressions in logarithmic space. However, the uncertainty structure of such regressions is frequently treated incorrectly, because measurement uncertainties in τ are absolute and approximately wavelength-independent in linear space, and therefore become wavelength-dependent in logarithmic space. As a result, the measurement covariance matrix must be explicitly accounted for in log–log regression, although this is rarely done in practice. This study provides both a formal and a practical framework for estimating τ at non-measured wavelengths together with its associated uncertainty. A rigorous formulation is presented for linear and quadratic regression in logarithmic space, including the propagation of random and systematic (bias-related) errors from the original spectral measurements to the interpolated or extrapolated wavelength.
Sensitivity analyses based on synthetic aerosol optical depth spectra generated with the GRASP forward model are used to compare six different approaches for deriving τ(550) and τ(2000), including linear and quadratic regressions over different spectral ranges as well as the GRASP-AOD method. When the covariance matrix is treated correctly, quadratic log–log regression is found to be the most robust method for estimating τ(550), and its results become essentially independent of the chosen spectral range. In contrast, when the covariance matrix is neglected, the same regression becomes highly sensitive to the selected wavelengths, and artificially improved performance is obtained when restricting the fit to the central AERONET channels. These findings are confirmed using real AERONET observations. When the full covariance treatment is applied, differences between estimates obtained using different spectral ranges remain below 0.002 at all sites analysed. When it is ignored, root-mean-square differences exceeding 0.01 are observed at sites dominated by fine-mode aerosols.
Finally, the uncertainty propagation framework is applied to real data and shows that the uncertainty of interpolated τ follows the expected Beer–Lambert law governing sun-photometer measurements, scaling with optical air mass. This provides an independent validation of the formal error model. Overall, this work establishes a consistent methodology for spectral interpolation and extrapolation of τ, ensuring both accurate values and physically meaningful uncertainties for satellite validation and related applications.
How to cite: Torres, B., Dubovik, O., Toledano, C., Fuertes, D., Momoi, M., Kazadzis, S., Marbach, T., Lind, E., Roman, R., Veloso Varela, M., and Barreto, A.: Inferring aerosol optical depth at unmeasured wavelengths from ground-based spectral photometer data: uncertainty-consistent regression, sensitivity tests, and application to real data, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-13698, https://doi.org/10.5194/egusphere-egu26-13698, 2026.
