Dr. Ángel M. de Frutos

@article{García2025,

title = {Aerosol retrievals derived from a low-cost Calitoo sun-photometer taken on board a research vessel},

author = {Rosa D. García and África Barreto and Celia Rey and Eugenio Fraile-Nuez and Alba González-Vega and Sergio F. León-Luis and Antonio Alcantara and A. Fernando Almansa and Carmen Guirado-Fuentes and Pablo González-Sicilia and Victoria E. Cachorro and Frederic Bouchar},

url = {https://www.sciencedirect.com/science/article/pii/S1352231024005636},

doi = {https://doi.org/10.1016/j.atmosenv.2024.120888},

issn = {1352-2310},

year  = {2025},

date = {2025-01-15},

urldate = {2025-01-15},

journal = {Atmospheric Environment},

volume = {341},

pages = {120888},

abstract = {This study presents a comprehensive 5-year period assessment of aerosol optical depth (AOD) and Å ngströn Exponent (AE) data from a hand-held Calitoo sun photometer on board the Ángeles Alvariño research vessel. Observations spanned March 2018 to September 2023, focusing on key maritime regions such as the Canary Islands, coasts of North Africa, the Mediterranean, Portugal, the Cantabrian, and the Bay of Biscay. The Calitoo device measures solar irradiance at three wavelengths (465, 540, and 619 nm). Uncertainty analysis for Calitoo AOD retrievals was performed using the Monte Carlo method, yielding an expanded uncertainty (UAOD) ranging between 0.008 and 0.050 with a mean and standard deviation of 0.032 ± 0.008 for the three wavelengths. Our results also highlight the remarkable calibration stability of the Calitoo (< 2.6%) over this 5-year period. Calitoo AOD values were assessed using reference AOD data from Santa Cruz de Tenerife (the Canary Islands), El Arenosillo (Huelva), and Palma de Mallorca (the Balearic Islands) AERONET (Aerosol Robotic Network) stations. The comparison revealed a good agreement with correlation coefficients ranging from 0.727 to 0.917 and mean bias ranging from -0.030 to -0.001. Additionally, the Calitoo AOD data were compared with MODIS (Moderate Resolution Imaging Spectroradiometer) and CAMS-ECMWF (Copernicus Atmosphere Monitoring Service-European Centre for Medium-Range Weather Forecasts) aerosol products obtaining that Calitoo AOD values were generally lower, showing negative mean bias of -0.063 and -0.024, respectively. The aerosol characterizations using AE vs. AOD plots in the three maritime study regions using 5-years of non-routine Calitoo data are similar to the corresponding aerosol characterizations performed with simultaneous AERONET-Cimel data. These findings underscore Calitoo’s reliability for aerosol studies in regions where AERONET instruments or other aerosol networks are unavailable. Likewise, given the low cost of Calitoo photometers, they could be deployed onboard a large number of merchant and passenger ships or in other remote or under-monitored areas, providing near real-time AOD/AE data to enhance our understanding of aerosols processes or for model or satellite assimilation/validation.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{rs16203821,

title = {Retrieval of Solar Shortwave Irradiance from All-Sky Camera Images},

author = {Daniel González-Fernández and Roberto Román and David Mateos and Celia Herrero del Barrio and Victoria E. Cachorro and Gustavo Copes and Ricardo Sánchez and Rosa Delia García and Lionel Doppler and Sara Herrero-Anta and Juan Carlos Antuña-Sánchez and África Barreto and Ramiro González and Javier Gatón and Abel Calle and Carlos Toledano and Ángel Frutos},

url = {https://www.mdpi.com/2072-4292/16/20/3821},

doi = {10.3390/rs16203821},

issn = {2072-4292},

year  = {2024},

date = {2024-10-14},

urldate = {2024-01-01},

journal = {Remote Sensing},

volume = {16},

number = {20},

abstract = {The present work proposes a new model based on a convolutional neural network (CNN) to retrieve solar shortwave (SW) irradiance via the estimation of the cloud modification factor (CMF) from daytime sky images captured by all-sky cameras; this model is named CNN-CMF. To this end, a total of 237,669 sky images paired with SW irradiance measurements obtained by using pyranometers were selected at the following three sites: Valladolid and Izaña, Spain, and Lindenberg, Germany. This dataset was randomly split into training and testing sets, with the latter excluded from the training model in order to validate it using the same locations. Subsequently, the test dataset was compared with the corresponding SW irradiance measurements obtained by the pyranometers in scatter density plots. The linear fit shows a high determination coefficient (R2) of 0.99. Statistical analyses based on the mean bias error (MBE) values and the standard deviation (SD) of the SW irradiance differences yield results close to ?2% and 9%, respectively. The MBE indicates a slight underestimation of the CNN-CMF model compared to the measurement values. After its validation, model performance was evaluated at the Antarctic station of Marambio (Argentina), a location not used in the training process. A similar comparison between the model-predicted SW irradiance and pyranometer measurements yielded R2=0.95, with an MBE of around 2% and an SD of approximately 26%. Although the precision provided by the SD at the Marambio station is lower, the MBE shows that the model’s accuracy is similar to previous results but with a slight overestimation of the SW irradiance. Finally, the determination coefficient improved to 0.99, and the MBE and SD are about 3% and 11%, respectively, when the CNN-CMF model is used to estimate daily SW irradiation values.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{gonzalez2024CCNeural,

title = {A neural network to retrieve cloud cover from all-sky cameras: A case of study over Antarctica},

author = {Daniel González-Fernández and Roberto Román and Juan Carlos Antuña-Sánchez and Victoria E. Cachorro and Gustavo Copes and Sara Herrero-Anta and Celia Herrero del Barrio and África Barreto and Ramiro González and Ramón Ramos and Patricia Martín and David Mateos and Carlos Toledano and Abel Calle and Ángel Frutos},

url = {https://rmets.onlinelibrary.wiley.com/doi/abs/10.1002/qj.4834},

doi = {https://doi.org/10.1002/qj.4834},

year  = {2024},

date = {2024-08-28},

journal = {Quarterly Journal of the Royal Meteorological Society},

volume = {n/a},

number = {n/a},

abstract = {Abstract We present a new model based on a convolutional neural network (CNN) to predict daytime cloud cover (CC) from sky images captured by all-sky cameras, which is called CNN-CC. A total of 49,016 daytime sky images, recorded at different Spanish locations (Valladolid, La Palma, and Izaña) from two different all-sky camera types, are manually classified into different CC (oktas) values by trained researchers. Subsequently, the images are randomly split into a training set and a test set to validate the model. The CC values predicted by the CNN-CC model are compared with the observations made by trained people on the test set, which serve as reference. The predicted CC values closely match the reference values within ±$$ ± $$1?oktas in 99% of the cloud-free and overcast cases. Moreover, this percentage is above 93% for the rest of partially cloudy cases. The mean bias error (MBE) and standard deviation (SD) of the differences between the predicted and reference CC values are calculated, resulting in MBE=0.007$$ mathrmMBE=0.007 $$?oktas and SD=0.674$$ mathrmSD=0.674 $$?oktas. The MBE and SD are also represented for different intervals of measured aerosol optical depth and Ångström exponent values, revealing that the performance of the CNN-CC model does not depend on aerosol load or size. Once the model is validated, the CC obtained from a set of images captured every 5?min, from January 2018 to March 2022, at the Antarctic station of Marambio (Argentina) is compared against direct field observations of CC (not from images) taken at this location, which is not used in the training process. As a result, the model slightly underestimates the observations with an MBE of ?$$ - $$0.3?oktas. The retrieved data are analyzed in detail. The monthly and annual CC values are calculated. Overcast conditions are the most frequent, accounting for 46.5% of all observations throughout the year, rising to 64.5% in January. The annual mean CC value at this location is 5.5?oktas, with a standard deviation of approximately 3.1?oktas. A similar analysis is conducted, separating data by hours, but no significant diurnal cycles are observed except for some isolated months.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{Almansa2024b,

title = {The Langley ratio method, a new approach for transferring photometer calibration from direct sun measurements},

author = {A. F. Almansa and Á. Barreto and N. Kouremeti and R. González and A. Masoom and C. Toledano and J. Gröbner and R. D. García and Y. González and S. Kazadzis and S. Victori and Ó. Álvarez and F. Maupin and V. Carreño and V. E. Cachorro and E. Cuevas},

url = {https://amt.copernicus.org/articles/17/659/2024/},

doi = {10.5194/amt-17-659-2024},

year  = {2024},

date = {2024-01-26},

urldate = {2024-01-01},

journal = {Atmospheric Measurement Techniques},

volume = {17},

number = {2},

pages = {659–675},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{atmos15060635,

title = {The Recovery and Re-Calibration of a 13-Month Aerosol Extinction Profiles Dataset from Searchlight Observations from New Mexico, after the 1963 Agung Eruption},

author = {J.C. Antuña-Marrero and G.W. Mann and J. Barnes and A. Calle and S.S. Dhomse and V.E. Cachorro and T. Deshler and Z. Li and N. Sharma and L. Elterman},

url = {https://www.mdpi.com/2073-4433/15/6/635},

doi = {10.3390/atmos15060635},

issn = {2073-4433},

year  = {2024},

date = {2024-01-01},

urldate = {2024-01-01},

journal = {Atmosphere},

volume = {15},

number = {6},

abstract = {The recovery and re-calibration of a dataset of vertical aerosol extinction profiles of the 1963/64 stratospheric aerosol layer measured by a searchlight at 32°N in New Mexico, US, is reported. The recovered dataset consists of 105 aerosol extinction profiles at 550 nm that cover the period from December 1963 to December 1964. It is a unique record of the portion of the aerosol cloud from the March 1963 Agung volcanic eruption that was transported into the Northern Hemisphere subtropics. The data-recovery methodology involved re-digitizing the 105 original aerosol extinction profiles from individual Figures within a research report, followed by the re-calibration. It involves inverting the original equation used to compute the aerosol extinction profile to retrieve the corresponding normalized detector response profile. The re-calibration of the original aerosol extinction profiles used Rayleigh extinction profiles calculated from local soundings. Rayleigh and aerosol slant transmission corrections are applied using the MODTRAN code in transmission mode. Also, a best-estimate aerosol phase function was calculated from observations and applied to the entire column. The tropospheric aerosol phase function from an AERONET station in the vicinity of the searchlight location was applied between 2.76 to 11.7 km. The stratospheric phase function, applied for a 12.2 to 35.2 km altitude range, is calculated from particle-size distributions measured by a high-altitude aircraft in the vicinity of the searchlight in early 1964. The original error estimate was updated considering unaccounted errors. Both the re-calibrated aerosol extinction profiles and the re-calibrated stratospheric aerosol optical depth magnitudes showed higher magnitudes than the original aerosol extinction profiles and the original stratospheric aerosol optical depth, respectively. However, the magnitudes of the re-calibrated variables show a reasonable agreement with other contemporary observations. The re-calibrated stratospheric aerosol optical depth demonstrated its consistency with the tropics-to-pole decreasing trend, associated with the major volcanic eruption stratospheric aerosol pattern when compared to the time-coincident stratospheric aerosol optical depth lidar observations at Lexington at 42° N.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{Herrero-Anta2023,

title = {Retrieval of aerosol properties from zenith sky radiance measurements},

author = {Sara Herrero-Anta and Roberto Román and David Mateos and Ramiro González and Juan Carlos Antuña-Sánchez and Marcos Herreras-Giralda and Antonio Fernando Almansa and Daniel González-Fernández and Celia Herrero del Barrio and Carlos Toledano and Victoria Eugenia Cachorro and Ángel Máximo de Frutos},

url = {https://amt.copernicus.org/articles/16/4423/2023/},

doi = {10.5194/amt-16-4423-2023},

year  = {2023},

date = {2023-10-09},

urldate = {2023-10-09},

journal = {Atmospheric Measurement Techniques},

volume = {16},

number = {19},

pages = {4423–4443},

abstract = {This study explores the potential to retrieve aerosol properties with the GRASP algorithm (Generalized Retrieval of Atmosphere and Surface Properties) using as input measurements of zenith sky radiance (ZSR), which are sky radiance values measured in the zenith direction, recorded at four wavelengths by a ZEN-R52 radiometer. To this end, the ZSR measured at 440, 500, 675 and 870?nm by a ZEN-R52 (ZSRZEN), installed in Valladolid (Spain), is employed. This instrument is calibrated by intercomparing the signal of each channel with coincident ZSR values simulated (ZSRSIM) at the same wavelengths with a radiative transfer model (RTM). These simulations are carried out using the GRASP forward module as RTM and the aerosol information from a co-located CE318 photometer belonging to AERONET (AErosol RObotic NETwork) as input. The dark signal and the signal dependence on temperature are characterized and included in the calibration process. The uncertainties for each channel are quantified by an intercomparison with a co-located CE318 photometer, obtaining lower values for shorter wavelengths; they are between 3?% for 440?nm and 21?% for 870?nm. The proposed inversion strategy for the aerosol retrieval using the ZSRZEN measurements as input, i.e. so-called GRASP-ZEN, assumes the aerosol as an external mixture of five pre-calculated aerosol types. A sensitivity analysis is conducted using synthetic ZSRZEN measurements, pointing out that these measurements are sensitive to aerosol load and type. It also assesses that the retrieved aerosol optical depth (AOD) values in general overestimate the reference ones by 0.03, 0.02, 0.02 and 0.01 for 440, 500, 675 and 870?nm, respectively. The calibrated ZSRZEN measurements, recorded during 2.5 years at Valladolid, are inverted by the GRASP-ZEN strategy to retrieve some aerosol properties like AOD. The retrieved AOD shows a high correlation with respect to independent values obtained from a co-located AERONET CE318 photometer, with determination coefficients (r2) of 0.86, 0.85, 0.79 and 0.72 for 440, 500, 675 and 870?nm, respectively, and finding uncertainties between 0.02 and 0.03 with respect to the AERONET values. Finally, the retrieval of other aerosol properties, like aerosol volume concentration for total, fine and coarse modes (VCT, VCF and VCC, respectively), is also explored. The comparison against independent values from AERONET presents r2 values of 0.57, 0.56 and 0.66 and uncertainties of 0.009, 0.016 and 0.02?µm3?µm?2 for VCT, VCF and VCC, respectively},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{Barja2023,

title = {Surface shortwave cloud radiative effect of cumulus and stratocumulus-cumulus cloud types in the Caribbean area (Camagüey Cuba, 2010-2016)},

author = {Barja, B. and Rosas, J. and Cachorro, V. E. and Toledano, C. and Antuña-Marrero, J. C. and Estevan, R. and de Frutos, A.},

editor = {Atmósfera},

doi = {10.20937/ATM.52858},

year  = {2023},

date = {2023-01-01},

journal = {36},

volume = {(1)},

pages = {41–56},

abstract = {The effects of cumulus (Cu) clouds and the combination of stratocumulus-cumulus (Sc-Cu) clouds on solar radiation at the Earth’s surface were evaluated at Camagüey, Cuba, during a 6-yr period (from June 2010 to May 2016). Two methods to calculate the cloud radiative effect (CRE) were employed. The first method (CREm) uses solar irradiances in cloudy conditions from actinometric observations, where cloud information was also reported by visual observation. In the second method (CRE0) surface solar irradiances were estimated for both cloudy and clear sky conditions using a 1-D radiative transfer model, and cloud optical depth (COD) retrieved from an AERONET sun-photometer as the main input. A temporal correspondence criterion between COD retrievals and actinometric observations was performed in order to classify the COD of each cloud type. After the application of this criterion, the COD belonging to the optically thin clouds was removed. Finally, 255 and 732 COD observations for Cu and Sc-Cu, respectively, were found. Results show a statistically significant difference at the 95% confidence level between CRE calculated for Sc-Cu and Cu, using both methods. Mean values of CREm and CRE0 for Cu (Sc-Cu) were ?442 (?390) and ?460 (?417) Wm–2, respectively. CRE0 shows a linear relation with ln(COD), with stronger correlation at a lower solar zenith angle. The shortwave cloud effect efficiency (CEE) for the two cloud types sharply decreases with the increase of the COD value up to 20. For larger COD, the CEE is less sensitive to the increase of COD.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{rs15225362,

title = {Analysis of Daytime and Night-Time Aerosol Optical Depth from Solar and Lunar Photometry in Valladolid (Spain)},

author = {Celia Herrero del Barrio and David Mateos and Roberto Román and Ramiro González and Sara Herrero-Anta and Daniel González-Fernández and Abel Calle and Carlos Toledano and Victoria Eugenia Cachorro and Ángel Máximo De Frutos Baraja},

url = {https://www.mdpi.com/2072-4292/15/22/5362},

doi = {10.3390/rs15225362},

issn = {2072-4292},

year  = {2023},

date = {2023-01-01},

urldate = {2023-01-01},

journal = {Remote Sensing},

volume = {15},

number = {22},

abstract = {Aerosol optical depth (AOD) at night-time has become a hot topic in recent years due to the development of new instruments recording accurate ground-based lunar irradiance measurements, and the development of calibration methods and extraterrestrial irradiance models adapted to lunar photometry. This study uses all daytime and night-time AOD data available at Valladolid (Spain) from October 2016 to March 2022 in order to analyze its behavior and the added contribution of night data. The annual, monthly and daily AOD evolution is studied comparing daytime and night-time values and checking the correlation between them. For this purpose, the daily averages are computed, showing an annual pattern, with low AOD values throughout the year (mean value of AOD at 440 nm: 0.122), where winter months have the lower and summer the higher values, as observed in previous studies. All these AOD values are modulated by frequent desert dust events over the Iberian Peninsula, with a strong influence on daily and monthly mean values in February and March, where the strongest desert outbreaks occurred. The added new data confirm these results and the good correlation between daytime and night-time data. Also, a complete daily evolution is shown, observing that AOD and Ångström exponent (AE) mean values vary by only ±0.02 in 24 h, with a maximum value at 06:00 UTC and minimum at 18:00 UTC for both parameters.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{García2022b,

title = {Spectral Aerosol Radiative Forcing and Efficiency of the La Palma Volcanic Plume over the Izaña Observatory},

author = {R.D. García and O.E. García and E. Cuevas-Agulló and A. Barreto and V.E. Cachorro and C. Marrero and F. Almansa and R. Ramos and M. Pó},

url = {https://www.mdpi.com/2072-4292/15/1/173},

doi = {10.3390/rs15010173},

issn = {2072-4292},

year  = {2022},

date = {2022-12-28},

urldate = {2023-01-01},

journal = {Remote Sensing},

volume = {15(1)},

number = {17},

abstract = {On 19 September 2021, a volcanic eruption began on the island of La Palma (Canary Islands, Spain). The eruption has allowed the assessment of an unprecedented multidisciplinary study on the effects of the volcanic plume. This work presents the estimation of the spectral direct radiative forcing (ΔF) and efficiency (ΔFEff) from solar radiation measurements at the Izaña Observatory (IZO) located on the island of Tenerife (∼140 km from the volcano). During the eruption, the IZO was affected by different types of aerosols: volcanic, Saharan mineral dust, and a mixture of volcanic and dust aerosols. Three case studies were identified using ground-based (lidar) data, satellite-based (Sentinel-5P Tropospheric Monitoring Instrument, TROPOMI) data, reanalysis data (Modern-Era Retrospective Analysis for Research and Applications, version 2, MERRA-2), and backward trajectories (Flexible Trajectories, FLEXTRA), and subsequently characterised in terms of optical and micro-physical properties using ground-based sun-photometry measurements. Despite the ΔF of the volcanic aerosols being greater than that of the dust events (associated with the larger aerosol load present), the ΔFEff was found to be lower. The spectral ΔFEff values at 440 nm ranged between −1.9 and −2.6 Wm−2nm−1AOD−1 for the mineral dust and mixed volcanic and dust particles, and between −1.6 and −3.3 Wm−2nm−1AOD−1 for the volcanic aerosols, considering solar zenith angles between 30∘ and 70∘, respectively.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{Vaquero-Martínez2022,

title = {Comparison of CIMEL sun-photometer and ground-based GNSS integrated water vapor over south-western European sites},

author = {Javier Vaquero-Martínez and André F. Bagorrilha and Manuel Antón and Juan C. Antuña-Marrero and Victoria E. Cachorro},

url = {https://www.sciencedirect.com/science/article/pii/S0169809522002034},

doi = {https://doi.org/10.1016/j.atmosres.2022.106217},

issn = {0169-8095},

year  = {2022},

date = {2022-09-01},

urldate = {2022-01-01},

journal = {Atmospheric Research},

volume = {275},

pages = {106217},

abstract = {This work analyzes the integrated water vapor (IWV) measured at six Aerosol Robotic Network (AERONET) stations with nearby global navigation satellite system (GNSS) in the Iberian Peninsula for the period 2007–2018. It is shown that both instruments have a high correlation (R2 > 0.91), with small mbe below 1.5 mm and standard deviation (SD) below 2 mm. However, some dependences have been observed when MBE and SD are represented in bins of three variables: IWV, solar zenith angle (SZA), and aerosol optical depth (AOD). The greater or lesser amount of water vapor in the atmosphere seemed to be the more influential variable, increasing dry bias and SD with increasing IWV. Moreover, high SZA values were related to SD increases. A clear seasonal cycle for Cimel–GNSS differences was observed which was mainly related to IWV seasonal cycle. Additionally, AOD did not show a remarkable influence on Cimel–GNSS differences. Finally, the monthly differences are also analyzed with metadata information about Cimel device ID numbers, showing that, for long-term studies, this information can be very valuable.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{Antuña-Sánchez2022,

title = {ORION software tool for the geometrical calibration of all-sky cameras},

author = {J.C. Antuña-Sánchez and R. Román and J.L. Bosch and C. Toledano and D. Mateos and R. González and V.E. Cachorro and Ángel de Frutos},

doi = {10.1371/journal.pone.0265959},

year  = {2022},

date = {2022-03-31},

urldate = {2022-03-31},

journal = {PLoS ONE 17(3)},

abstract = {This paper presents the software application ORION (All-sky camera geOmetry calibRation from star positIONs). This software has been developed with the aim of providing geometrical calibration to all-sky cameras, i.e. assess which sky coordinates (zenith and azimuth angles) correspond to each camera pixel. It is useful to locate bodies over the celestial vault, like stars and planets, in the camera images. The user needs to feed ORION with a set of cloud-free sky images captured at night-time for obtaining the calibration matrices. ORION searches the position of various stars in the sky images. This search can be automatic or manual. The sky coordinates of the stars and the corresponding pixel positions in the camera images are used together to determine the calibration matrices. The calibration is based on three parameters: the pixel position of the sky zenith in the image; the shift angle of the azimuth viewed by the camera with respect to the real North; and the relationship between the sky zenith angle and the pixel radial distance regards to the sky zenith in the image. In addition, ORION includes other features to facilitate its use, such as the check of the accuracy of the calibration. An example of ORION application is shown, obtaining the calibration matrices for a set of images and studying the accuracy of the calibration to predict a star position. Accuracy is about 9.0 arcmin for the analyzed example using a camera with average resolution of 5.4 arcmin/pixel (about 1.7 pixels).},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{Cachorro2022,

title = {SSolar-GOA v1.0: a simple, fast, and accurate Spectral SOLAR radiative transfer model for clear skies},

author = {V. E. Cachorro and J. C. Antuña-Sanchez and Á. M. Frutos},

url = {https://gmd.copernicus.org/articles/15/1689/2022/},

doi = {10.5194/gmd-15-1689-2022},

year  = {2022},

date = {2022-02-25},

urldate = {2022-02-25},

journal = {Geoscientific Model Development},

volume = {15},

number = {4},

pages = {1689--1712},

abstract = {The aim of this work is to describe the features of and to validate a simple, fast, accurate, and physically based spectral radiative transfer model in the solar wavelength range under clear skies. The model, named SSolar-GOA (the first “S” stands for “spectral”), was developed to evaluate the instantaneous values of spectral solar irradiances at ground level or at a given altitude of the atmosphere. The model requirements are designed based on the simplicity of the analytical expressions for the transmittance functions in order to be easily replicated and applied by a wide community of users for many different applications (atmospheric and environmental research studies, satellite remote sensing, solar energy, agronomy and forestry, ecology, and others). Although spectral, the model runs quickly and has sufficient accuracy for the evaluation of solar irradiances with a spectral resolution of 1–10?nm. The model assumes a single mixed molecule–aerosol scattering layer where the original Ambartsumian method of “adding layers” in a one-dimensional medium is applied, obtaining a parameterized expression for the total transmittance of scattering. Absorption by the different atmospheric gases follows “band model” parameterized expressions. The input parameters must be realistic and easily available since the spectral aerosol optical depth (AOD) is the main driver of the model. The validation of the SSolar-GOA model has been carried out through comparison with simulated irradiance data from the libRadtran package and with direct and global spectra measured by spectroradiometers. Thousands of spectra under clear skies have been compared for different atmospheric conditions and solar zenith angles (SZA). The SSolar-GOA is validated by a quantitative comparison with libRadtran, showing that it underestimates direct normal, global, and diffuse spectral components with relative differences of +1?% (RMSE?%?=?4.6–8), +3?% (RMSE?%?=?5.3–8), and 8?% (RMSE?%?=?9.3–9.6), respectively, when the SZA varies from 6 to 60?. Compared with the measured irradiance data of the LI-1800 and ASD spectroradiometers, the relative differences of direct normal and global components are within the overall experimental error, about ±2?%–12?% (RMSE?%?=?5–8.3), with underestimated or overestimated values. The diffuse component presents the highest degree of relative difference that can reach ±20?%–30?% and RMSE of 25?%–50?%. The relative differences depend strongly on the spectral solar region analysed and the SZA, but the high values of RMSE are due to the artifice generated by the different spectral resolution of the absorption coefficients of both models. Model approach errors combined with calibration instrument errors may explain the observed differences. The SSolar-GOA v1.0 is implemented in Python and open-source licensing.},

keywords = {},

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tppubtype = {article}

}