Dr. Roberto Román

@article{Montero-Martín2023,

title = {Reconstruction of daily global solar radiation under all-sky and cloud-free conditions in Badajoz (Spain) since 1929},

author = {Javier Montero-Martín and Manuel Antón and José Manuel Vaquero and Roberto Román and Javier Vaquero-Martinez and Alejandro J. P. Aparicio and Arturo Sanchez-Lorenzo},

url = {https://rmets.onlinelibrary.wiley.com/doi/abs/10.1002/joc.8042},

doi = {https://doi.org/10.1002/joc.8042},

year  = {2023},

date = {2023-02-16},

journal = {International Journal of Climatology},

volume = {n/a},

number = {n/a},

abstract = {Abstract This work analyses the long-term temporal variability of the annual and seasonal series of reconstructed global solar radiation for both all-sky and cloud-free conditions in Badajoz (Spain) over the 1929–2015 period. Specifically, daily values of global horizontal irradiation (GHI) for all-sky cases are derived from a semiempirical method based on the relationship between the cloud modification factor and sunshine duration records. Additionally, cloud-free situations are selected using cloud cover (CC) information recorded by surface observations. Regarding GHI linear trends for all-sky conditions, three periods are clearly identified: during the 1929–1950 period, there is a positive and statistically significant trend of +4.18?W·m?2·decade?1. It is followed by a significant dimming with a trend of ?3.72?W·m?2·decade?1 between 1951 and 1984. GHI levels increase again from 1985 to 2015 with a statistically significant trend of +2.04?W·m?2·decade?1. The seasonal trends are found to be statistically significant only in summer for all the three subperiods. With the goal to find out the possible causes of the reconstructed GHI trends, the temporal variability of the CC was also analysed. It was observed that CC has a statistically significant negative trend between 1985 and 2015 which may partially explain the GHI increase shown for this period. In contrast, not statistically significant trends were found in the annual and seasonal CC series before 1985. The long-term evolution of the GHI under cloud-free conditions exhibits the same pattern as all-sky conditions: an increase during 1929–1950, followed by a decrease in 1951–1984 and then a new increase from 1985 to 2015. Therefore, the positive (negative) linear trends in GHI reported in this study could be partially related to a decrease (increase) in the aerosol load during the analysed three subperiods.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{Bazo2023,

title = {Evaluation of the vertically-resolved aerosol radiative effect on shortwave and longwave ranges using sun-sky photometer and ceilometer measurements},

author = {Elena Bazo and María J. Granados-Muñoz and Roberto Román and Juan Antonio Bravo-Aranda and Alberto Cazorla and Antonio Valenzuela and Ramiro González and Francisco José Olmo and Lucas Alados-Arboledas},

url = {https://www.sciencedirect.com/science/article/pii/S0169809522005038},

doi = {https://doi.org/10.1016/j.atmosres.2022.106517},

issn = {0169-8095},

year  = {2023},

date = {2023-01-01},

urldate = {2023-01-01},

journal = {Atmospheric Research},

volume = {282},

pages = {106517},

abstract = {The aerosol radiative effect (ARE) is one of the atmospheric components still affected by large uncertainty. One of the causes is related to the fact that the longwave (LW) component is usually neglected, even though it is necessary for an accurate quantification of the ARE together with the shortwave component (SW). In this study we have developed a methodology based on the GAME (Global Atmospheric Model) radiative transfer model (RTM) that allows to obtain the radiative effect of the atmospheric aerosol for both spectral ranges in an automated way. The microphysical and optical properties necessary to feed the RTM have been obtained through the GRASP (Generalized Retrieval of Aerosol and Surface Properties) algorithm, with the combination of ceilometer and sun-sky photometer data. Data measured in Granada (Spain) during 2017 have been used for the evaluation and implementation of this methodology. According to the results, the ARE in the SW spectral range (ARESW) varies between 0 and ? 50 Wm?2 for most of the data, whereas the ARE in the LW range (ARELW) varies between 0 and 5 Wm?2, at heights near the surface. In general, the obtained results agree with those found in the literature, with negative values in the SW range (cooling effect) and positive values in the LW (heating effect). The seasonal analysis shows that, for both components, the ARE is more important during the spring and summer seasons, when the aerosol load is greater, as expected. The analysis of the aerosol heating rate (AHR) shows positive values in the SW and negative values in the LW range. The majority of the AHRSW data varies between 0 and 1 Kd?1 during the year whereas the AHRLW does it between 0 and ? 0.15 Kd?1. The seasonal analysis of the AHR shows that the greater monthly average values are found during spring, however there is not much variability along the year, with the exception of February, under the effects of an extreme dust intrusion. The mineral dust particles in this event cause an ARESW of ?130 Wm?2 and an ARELW of 23 Wm?2 (ARELW/ARESW = 17%), thus pointing out that the LW component should not be neglected for coarse mode particles. Additionally, it is observed that the vertical distribution of the aerosol layers strongly influences the ARE and the AHR obtained profiles, affecting the way the atmospheric cooling/heating occurs in the vertical coordinate.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{García2022,

title = {La erupción volcánica de La Palma y el papel de la Agencia Estatal de Meteorología},

author = {García, O. and Suárez, D. and Cuevas, E. and Ramos, R. and Barreto, Á. and Hernández, M. and Quintero, V. and Toledano, C. and Sicard, M. and Córdoba-Jabonero, C. and Riz, V. and Roininen, R. and López, C. and Vilches, J. and Weiss, M. and Carreño, V. and Taquet, N. and Boulesteix, T. and Fraile, E. and Torres, C. and Prats, N. and Alcántara, A. and León, S. and Rivas, P. and Álvarez, Ó. and Parra, F. and de Luis, J. and González, C. and Armas, C. and Romero, P. and de Bustos, J. and Redondas, A. and Marrero, C. and Milford, C. and Román, R. and González, R. and López-Cayuela, M. and Carvajal-Pérez, C. and Chinea, N. and García, R. and Almansa, F. and González, Y. and Bullón, F. and Poggio, M. and Rivera, C. and Bayo, C. and Rey, F.},

url = {https://pub.ame-web.org/index.php/TyC/article/view/2516},

year  = {2022},

date = {2022-05-04},

journal = { Revista Tiempo Y Clima},

volume = {5},

number = {76},

abstract = {Durante la erupción del volcán de Cumbre Vieja, en la isla de La Palma en 2021, la Agencia Estatal de Meteorología (AEMET), en calidad de Servicio Nacional y Autoridad Meteorológica del Estado, prestó diferentes servicios de apoyo al Comité Científico y al Comité Asesor del Plan de Emergencias Volcánicas de Canarias (PEVOLCA). Parte de sus actividades abarcaron la vigilancia y predicción meteorológica, la monitorización y predicción del transporte del penacho volcánico, y la valoración del impacto de las emisiones de gases y cenizas de la erupción volcánica en la calidad del aire en la isla de La Palma y en la región de Canarias.},

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{Antuña-Marrero2022,

title = {Integrated water vapor over the Arctic: Comparison between radiosondes and sun photometer observations},

author = {Juan Carlos Antuña-Marrero and Roberto Román and Victoria E. Cachorro and David Mateos and Carlos Toledano and Abel Calle and Juan Carlos Antuña-Sánchez and Javier Vaquero-Martínez and Manuel Antón and Ángel M. Frutos Baraja},

url = {https://www.sciencedirect.com/science/article/pii/S016980952200045X},

doi = {https://doi.org/10.1016/j.atmosres.2022.106059},

issn = {0169-8095},

year  = {2022},

date = {2022-02-02},

urldate = {2022-01-01},

journal = {Atmospheric Research},

volume = {270},

pages = {106059},

abstract = {The amplification of global warming because of the feedbacks associated with the increase in atmospheric moisture and the decrease in sea ice and snow cover in the Arctic is currently the focus of scientists, policy makers and society. The amplification of global warming is the response to increases in precipitation originally caused by climate change. Arctic predominant increases in specific humidity and precipitation have been documented by observations. In comparison, evapotranspiration in the Arctic is poorly known, in part, because the spatial and temporal sparsity of accurate in situ and remote sensing observations. Although more than 20 observations sites in the Arctic are available, where AERONET sun photometer integrated water vapor (IWV) measurements have been conducted, that information have been barely used. Here, we present a comparison of IWV observations from radiosondes and AERONET sun photometers at ten sites located across the Arctic with the goal to document the feasibility of that set of observations to contribute to the ongoing and future research on polar regions. Sun photometer IWV observations are averaged for three-time windows; 30 min, 6 and 24 h. The predominant dry bias of AERONET IWV observations with respect to radiosondes, identified at tropical and midlatitudes, is also present in the Arctic. The statistics of the comparison show robust results at eight of the ten sites, with precision and accuracy magnitudes below 8 and 2% respectively. The possible causes of the less robust results at the other two sites are discussed. In addition, the impact of selecting other temporal coincidence windows in the average sun photometer IWV used in the comparison were tested. Auto-correlation in diurnal sun photometer IWV could produce appreciable bias in the statistics used for the comparison. We suggest using only one pair of values per day, consisting in the daily mean IWV sun photometer and the IWV radiosonde observation value. This feature should be valid also for comparison of IWV from sun photometer and other instruments. Maximum 10% error level of IWV from sun photometer observations, when compared with radiosondes, have been found for the Arctic. It is in the same order of magnitude than at tropical and middle latitudes locations. It has been demonstrated the feasibility of AERONET IWV observations in the Arctic for research on this variable. AERONET standard instruments and its centralized-standard processing algorithm allow its IWV observations to be considered a relative standard dataset for the re-calibration of other instrumental IWV observations assuming radiosondes as the absolute standard dataset.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{Román2022,

title = {Retrieval of aerosol properties using relative radiance measurements from an all-sky camera},

author = {R. Román and J. C. Antuña-Sánchez and V. E. Cachorro and C. Toledano and B. Torres and D. Mateos and D. Fuertes and C. López and R. González and T. Lapionok and M. Herreras-Giralda and O. Dubovik and Á. M. Frutos},

url = {https://amt.copernicus.org/articles/15/407/2022/},

doi = {10.5194/amt-15-407-2022},

year  = {2022},

date = {2022-01-27},

urldate = {2022-01-01},

journal = {Atmospheric Measurement Techniques},

volume = {15},

number = {2},

pages = {407--433},

abstract = {This paper explores the potential of all-sky cameras to retrieve aerosol properties with the GRASP code (Generalized Retrieval of Atmosphere and Surface Properties). To this end, normalized sky radiances (NSRs) extracted from an all-sky camera at three effective wavelengths (467, 536 and 605?nm) are used in this study. NSR observations are a set of relative (uncalibrated) sky radiances in arbitrary units. NSR observations have been simulated for different aerosol loads and types with the forward radiative transfer module of GRASP, indicating that NSR observations contain information about the aerosol type, as well as about the aerosol optical depth (AOD), at least for low and moderate aerosol loads. An additional sensitivity study with synthetic data has been carried out to quantify the theoretical accuracy and precision of the aerosol properties (AOD, size distribution parameters, etc.) retrieved by GRASP using NSR observations as input. As a result, the theoretical accuracy of AOD is within ±0.02 for AOD values lower than or equal to 0.4, while the theoretical precision goes from 0.01 to 0.05 when AOD at 467?nm varies from 0.1 to 0.5. NSR measurements recorded at Valladolid (Spain) with an all-sky camera for more than 2 years have been inverted with GRASP. The retrieved aerosol properties are compared with independent values provided by co-located AERONET (AErosol RObotic NETwork) measurements. AODs from both data sets correlate with determination coefficient (r2) values of about 0.87. Finally, the novel multi-pixel approach of GRASP is applied to daily camera radiances together by constraining the temporal variation in certain aerosol properties. This temporal linkage (multi-pixel approach) provides promising results, reducing the highly temporal variation in some aerosol properties retrieved with the standard (one by one or single-pixel) approach. This work implies an advance in the use of all-sky cameras for the retrieval of aerosol properties.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{Benavent-Oltra2021,

title = {Overview of the SLOPE I and II campaigns: aerosol properties retrieved with lidar and sun--sky photometer measurements},

author = {J A Benavent-Oltra and J A Casquero-Vera and R Román and H Lyamani and D Pérez-Ramírez and M J Granados-Muñoz and M Herrera and A Cazorla and G Titos and P Ortiz-Amezcua and A E Bedoya-Velásquez and G de Arruda Moreira and N Pérez and A Alastuey and O Dubovik and J L Guerrero-Rascado and F J Olmo-Reyes and L Alados-Arboledas},

url = {https://acp.copernicus.org/articles/21/9269/2021/},

doi = {10.5194/acp-21-9269-2021},

year  = {2021},

date = {2021-06-17},

journal = {Atmospheric Chemistry and Physics},

volume = {21},

number = {12},

pages = {9269-9287},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{amt-14-2201-2021,

title = {Relative sky radiance from multi-exposure all-sky camera images},

author = {J C Antuña-Sánchez and R Román and V E Cachorro and C Toledano and C López and R González and D Mateos and A Calle and Á M de Frutos},

url = {https://amt.copernicus.org/articles/14/2201/2021/},

doi = {10.5194/amt-14-2201-2021},

year  = {2021},

date = {2021-03-22},

journal = {Atmospheric Measurement Techniques},

volume = {14},

number = {3},

pages = {2201--2217},

abstract = {All-sky cameras are frequently used to detect cloud cover; however, this work explores the use of these instruments for the more complex purpose of extracting relative sky radiances. An all-sky camera (SONA202-NF model) with three colour filters narrower than usual for this kind of cameras is configured to capture raw images at seven exposure times. A detailed camera characterization of the black level, readout noise, hot pixels and linear response is carried out. A methodology is proposed to obtain a linear high dynamic range (HDR) image and its uncertainty, which represents the relative sky radiance (in arbitrary units) maps at three effective wavelengths. The relative sky radiances are extracted from these maps and normalized by dividing every radiance of one channel by the sum of all radiances at this channel. Then, the normalized radiances are compared with the sky radiance measured at different sky points by a sun and sky photometer belonging to the Aerosol Robotic Network (AERONET). The camera radiances correlate with photometer ones except for scattering angles below 10?, which is probably due to some light reflections on the fisheye lens and camera dome. Camera and photometer wavelengths are not coincident; hence, camera radiances are also compared with sky radiances simulated by a radiative transfer model at the same camera effective wavelengths. This comparison reveals an uncertainty on the normalized camera radiances of about 3.3?%, 4.3?% and 5.3?% for 467, 536 and 605?nm, respectively, if specific quality criteria are applied.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{bedoya2021ceilometer,

title = {Ceilometer inversion method using water-vapor correction from co-located microwave radiometer for aerosol retrievals},

author = {AE Bedoya-Velásquez and M Herreras-Giralda and R Román and M Wiegner and S Lefebvre and C Toledano and T Huet and R Ceolato},

doi = {10.1016/j.atmosres.2020.105379},

year  = {2021},

date = {2021-03-01},

journal = {Atmospheric Research},

pages = {105379},

publisher = {Elsevier},

abstract = {Recent ceilometer models are more sensitive to aerosols, which is increasing the interest in these instruments to retrieve aerosol optical and microphysical properties. In this paper, a new methodology is proposed to retrieve aerosol vertical extinction and backscatter profiles from a Vaisala ceilometer CL51 model. This methodology is based in two parts: first, a signal pre-processing with a suppression of the dark current and background noises, and a correction of the water vapor absorption using near-real-time temperature and absolute humidity (AH) profiles from a co-located Microwave radiometer (MWR). The measured dark current shows a height-dependence from 11?km agl to the end of the profile. From the water vapor correction, it was seen that the raw ceilometer signal overestimates the water vapor corrected one, mainly below 1?km agl. Second part is based on an iterative Klett-based algorithm making use of AERONET (AErosol RObotic NETwork) AOD (Aerosol Optical Depth) and ceilometer profiles as inputs to retrieve the extinction and backscatter profiles. The sensitivity of the aerosol retrievals to the use of modelled temperature and absolute humidity from HYSPLIT to correct water vapor absorption, instead of MWR measurements, is studied. The absolute errors found in temperature and AH profiles leads to errors in the pre-processed range corrected signals up to 9%, and then in particle backscatter (?p) and particle extinction (?p) coefficients up to 2.2 % and 25 %, respectively.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{rs13020169,

title = {Solar Radiation Climatology in Camagüey, Cuba (1981–2016)},

author = {Juan Carlos Antuña-Sánchez and René Estevan and Roberto Román and Juan Carlos Antuña-Marrero and Victoria E Cachorro and Albeth Rodríguez Vega and Ángel M de Frutos},

url = {https://www.mdpi.com/2072-4292/13/2/169},

doi = {10.3390/rs13020169},

issn = {2072-4292},

year  = {2021},

date = {2021-01-01},

journal = {Remote Sensing},

volume = {13},

number = {2},

abstract = {The transition to renewable energies is an unavoidable step to guarantee a peaceful and sustainable future for humankind. Although solar radiation is one of the main sources of renewable energy, there are broad regions of the planet where it has not been characterized appropriately to provide the necessary information for regional and local planning and design of the different solar powered systems. The Caribbean, and Cuba in particular, lacked until very recently at least one long-term series of surface solar radiation measurements. Here we present the first long-term records of solar radiation for this region. Solar radiation measurements manually conducted and recorded on paper were rescued, reprocessed and quality controlled to develop the solar radiation climatology at the Actinometrical Station of Camagüey, in Cuba (21.422°N; 77.850°W; 122 m a.s.l.) for the period 1981-2016. The diurnal cycle based on the average hourly values of the global, direct and diffuse horizontal variables for the entire period have been determined and analyzed showing the dependence on solar zenith angle (SZA) and clouds. The annual cycle of global solar component given by the mean monthly daily values presents two maxima, one in April and another one in July with values of 5.06 and 4.91 kWh m−2, respectively (18.23 and 17.67 MJ m−2 per day for insolation), and the minimum in December (3.15 kWh m−2 or 11.33 MJ m−2). The maxima are governed by the direct solar components and are modulated by cloudiness. Both, diurnal and annual cycles of the diffuse solar component show a smoothed bell shaped behavior. In general solar radiation at this station presents a strong influence of clouds, with little seasonal variation but with higher values during the rainy season. Daily global radiation annual averages showed its maximum value in the year 1983, with 17.45 MJ m−2 explained by very low cloudiness this year, and the minimum value was reported in 2009 with a value of 12.43 MJ m−2 that could not explained by the cloud coverage or the aerosols optical depths registered that year. The effects of the 1982 El Chichón and 1991 Mount Pinatubo volcanic eruptions on the solar radiation variables at Camagüey are also shown and discussed. The results achieved in this study shown the characteristics of solar radiation in this area and their potential for solar power applications.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{gonzalez2020daytime,

title = {Daytime and nighttime aerosol optical depth implementation in CÆLIS},

author = {Ramiro González and Carlos Toledano and Roberto Román and David Fuertes and Alberto Berjón and David Mateos and Carmen Guirado-Fuentes and Cristian Velasco-Merino and Juan Carlos Antuña-Sánchez and Abel Calle and Victoria E. Cachorro and Angel M. de Frutos},

doi = {10.5194/gi-9-417-2020},

year  = {2020},

date = {2020-01-01},

urldate = {2020-01-01},

journal = {Geoscientific Instrumentation, Methods and Data Systems},

volume = {9},

number = {2},

pages = {417--433},

publisher = {Copernicus GmbH},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{rs12223769,

title = {Characterization of Stratospheric Smoke Particles over the Antarctica by Remote Sensing Instruments},

author = {Ramiro González and Carlos Toledano and Roberto Román and David Mateos and Eija Asmi and Edith Rodríguez and Ian C Lau and Jonathan Ferrara and Raúl D’Elia and Juan Carlos Antuña-Sánchez and Victoria E Cachorro and Abel Calle and Ángel M de Frutos},

url = {https://www.mdpi.com/2072-4292/12/22/3769},

doi = {10.3390/rs12223769},

issn = {2072-4292},

year  = {2020},

date = {2020-01-01},

journal = {Remote Sensing},

volume = {12},

number = {22},

abstract = {Australian smoke from the extraordinary biomass burning in December 2019 was observed over Marambio, Antarctica from the 7th to the 10th January, 2020. The smoke plume was transported thousands of kilometers over the Pacific Ocean, and reached the Antarctic Peninsula at a hight of 13 km, as determined by satellite lidar observations. The proposed origin and trajectory of the aerosol are supported by back-trajectory model analyses. Ground-based Sun-Sky-Moon photometer belonging to the Aerosol Robotic Network (AERONET) measured aerosol optical depth (500 nm wavelength) above 0.3, which is unprecedented for the site. Inversion of sky radiances provide the optical and microphysical properties of the smoke over Marambio. The AERONET data near the fire origin in Tumbarumba, Australia, was used to investigate the changes in the measured aerosol properties after transport and ageing. The analysis shows an increase in the fine mode particle radius and a reduction in absorption (increase in the single scattering albedo). The available long-term AOD data series at Marambio suggests that smoke particles could have remained over Antarctica for several weeks after the analyzed event.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{acp-20-14253-2020,

title = {New particle formation at urban and high-altitude remote sites in the south-eastern Iberian Peninsula},

author = {J A Casquero-Vera and H Lyamani and L Dada and S Hakala and P Paasonen and R Román and R Fraile and T Petäjä and F J Olmo-Reyes and L Alados-Arboledas},

url = {https://acp.copernicus.org/articles/20/14253/2020/},

doi = {10.5194/acp-20-14253-2020},

year  = {2020},

date = {2020-01-01},

journal = {Atmospheric Chemistry and Physics},

volume = {20},

number = {22},

pages = {14253--14271},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{vaquero2020water,

title = {Water vapor satellite products in the European Arctic: An inter-comparison against GNSS data},

author = {Javier Vaquero-Martínez and Manuel Antón and Roberto Román and Victoria E Cachorro and Huiqun Wang and Gonzalo González Abad and Christoph Ritter},

url = {https://www.sciencedirect.com/science/article/pii/S0048969720338572},

doi = {10.1016/j.scitotenv.2020.140335},

year  = {2020},

date = {2020-01-01},

journal = {Science of The Total Environment},

volume = {741},

pages = {140335},

publisher = {Elsevier},

keywords = {},

pubstate = {published},

tppubtype = {article}

}