Configuración y metodología para el uso de cámaras de todo cielo en la obtención de parámetros atmosféricos.

Atmospheric aerosols, solid or liquid particles floating in the atmosphere, play an important role in the Earth's climate, since they scatter and absorb part of the solar radiation reaching the Earth. The aerosol properties are usually obtained by measuring the diffuse solar radiation incoming in different directions (sky radiance), which is partially formed by the scattering of aerosols. The sky radiance is usually measured with photometers. A cheaper alternative to these photometers are the all-sky cameras, which capture images of the whole sky. In this doctoral thesis we propose the use of all-sky cameras to retrieve atmospheric parameters like the sky radiance and some aerosol properties, which can be obtained from these radiances. In this work, the ORION application has been developed to calibrate geometrically the all-sky cameras through the position of the stars. These calibrations are essential to locate the pixels of the camera pointing to a specific direction, such as the directions in which the sky radiance will be extracted. An all-sky camera has been geometrically calibrated with ORION, but it also has been configured to capture images in RAW format at different exposure times. The multi-exposure configuration, in addition with a exhaustive characterization of the camera (effective wavelengths, linearity, read noise, etc.), has allowed to obtain a linear high dynamic range image of the sky applying a proposed methodology. The sky radiance is proportional to the linear image obtained, so a relative sky radiance can be obtained with this proposed methodology. Once the relative sky radiances have been obtained with the all-sky camera, they have been used as input parameter in the GRASP (Generalized Retrieval of Atmosphere and Surface Properties) inversion algorithm to obtain some aerosol properties. It has been studied, using synthetic data, what aerosol properties can be derived from the relative sky radiance measured by all-sky cameras. The aerosol properties obtained with real measurements on GRASP have been compared with those independently derived by an AERONET (AErosol RObotic NETwork) photometer. This work concludes that, if the methodologies developed in this doctoral thesis are applied, a properly configured all-sky camera can be used to calculate the sky radiance, at least in a relative way, and these radiances can be also used to retrieve aerosol properties.Los aerosoles atmosféricos, partículas sólidas o líquidas en suspensión, juegan un papel muy relevante en el clima de la Tierra, ya que dispersan y absorben parte de la radiación solar que llega al planeta. Las propiedades de los aerosoles se suelen derivar midiendo la radiación solar difusa que llega en distintas direcciones (radiancia del cielo), la cual es causada en parte por la dispersión de los aerosoles. La radiancia del cielo se mide generalmente con fotómetros. Una alternativa económica a estos fotómetros son las cámaras de todo cielo, o simplemente cámaras de cielo, que capturan imágenes del cielo en toda la bóveda celeste. En esta tesis doctoral se propone el uso de las cámaras de cielo para obtener parámetros atmosféricos como la radiancia del cielo y algunas propiedades de los aerosoles, las cuales se pueden inferir a partir de esas radiancias. En este trabajo se ha desarrollado la aplicación ORION para calibrar geométricamente las cámaras de cielo a través de la posición de las estrellas. Estas calibraciones son fundamentales para poder localizar los píxeles de una cámara que apuntan a una dirección concreta, como las direcciones en las que se va a extraer la radiancia del cielo. Con ORION se ha calibrado geométricamente una cámara de cielo, la cual se ha configurado para capturar imágenes en formato RAW a varios tiempos de exposición. La configuración multi-exposición, en conjunto con una caracterización exhaustiva de la cámara (longitudes de onda efectivas, linealidad, ruido de lectura, etc.), ha permitido obtener una imagen lineal de alto rango dinámico del cielo gracias a una metodología propuesta. La radiancia del cielo es proporcional a la imagen lineal obtenida, por lo que con la metodología propuesta se puede obtener una radiancia del cielo relativa. Una vez obtenidas las radiancias relativas con la cámara de cielo, estas se han usado como parámetro de entrada en el algoritmo de inversión GRASP (Generalized Retrieval of Atmosphere and Surface Properties) para obtener propiedades de los aerosoles. A partir de datos sintéticos, se ha estudiado que propiedades de los aerosoles se pueden derivar de estas medidas. Las propiedades obtenidas con medidas reales en GRASP se han comparado con las derivadas independientemente por un fotómetro de AERONET (AErosol RObotic NETwork). Como resultado se ha concluido que, si se aplican las metodologías desarrolladas en esta tesis doctoral, una cámara de cielo configurada adecuadamente puede usarse para calcular la radiancia del cielo, al menos de manera relativa, y éstas radiancias para inferir propiedades de los aerosoles.Escuela de DoctoradoDoctorado en Físic

Integrated water vapor over the Arctic: Comparison between radiosondes and sun photometer observations

Producción CientíficaThe 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.Ministerio de Ciencia, Innovación y Universidades (grant RTI2018-097864-B-I00)Junta de Castilla y León (grant VA227P20)Junta de Extremadura - Fondo Europeo de Desarrollo Regional (grant GR21080 and project IB18092

Daytime and nighttime aerosol optical depth implementation in CÆLIS

The University of Valladolid (UVa, Spain) has managed a calibration center of the AErosol RObotic NETwork (AERONET) since 2006. The CÆLIS software tool, developed by UVa, was created to manage the data generated by AERONET photometers for calibration, quality control and data processing purposes. This paper exploits the potential of this tool in order to obtain products like the aerosol optical depth (AOD) and Ångström exponent (AE), which are of high interest for atmospheric and climate studies, as well as to enhance the quality control of the instruments and data managed by CÆLIS. The AOD and cloud screening algorithms implemented in CÆLIS, both based on AERONET version 3, are described in detail. The obtained products are compared with the AERONET database. In general, the differences in daytime AOD between CÆLIS and AERONET are far below the expected uncertainty of the instrument, ranging in mean differences between −1.3×10−4 at 870 nm and 6.2×10−4 at 380 nm. The standard deviations of the differences range from 2.8×10−4 at 675 nm to 8.1×10−4 at 340 nm. The AOD and AE at nighttime calculated by CÆLIS from Moon observations are also presented, showing good continuity between day and nighttime for different locations, aerosol loads and Moon phase angles. Regarding cloud screening, around 99.9 % of the observations classified as cloud-free by CÆLIS are also assumed cloud-free by AERONET; this percentage is similar for the cases considered cloud-contaminated by both databases. The obtained results point out the capability of CÆLIS as a processing system. The AOD algorithm provides the opportunity to use this tool with other instrument types and to retrieve other aerosol products in the future. This research has been supported by the Spanish Ministry of Science and Innovation (grant no. RTI2018-097864-B-I00) and the European Union's Horizon 2020 research and innovation program (grant no. 871115).The authors gratefully thank AERONET and PHOTONS teams for the collaboration and support. The authors thank the Spanish Ministry of Science, Innovation and Universities for the support through the ePOLAAR project (RTI2018-097864-B-I00). This research has been supported by the Spanish Ministry of Science and Innovation (grant no. RTI2018-097864-B-I00) and the European Union's Horizon 2020 research and innovation program (grant no. 871115)

Characterization of stratospheric smoke particles over the antarctica by remote sensing instruments

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.Fil: González, Ramiro. Universidad de Valladolid; EspañaFil: Toledano, Carlos. Universidad de Valladolid; EspañaFil: Román, Roberto. Universidad de Valladolid; EspañaFil: Mateos, David. Universidad de Valladolid; EspañaFil: Asmi, Eija Maria. Finnish Meteorological Institute; Finlandia. Ministerio de Defensa. Secretaria de Planeamiento. Servicio Meteorológico Nacional; ArgentinaFil: Rodríguez, Edith. Finnish Meteorological Institute; FinlandiaFil: Lau, Ian C.. Commonwealth Scientific And Industrial Research Organisation Astronomy And Space Science; AustraliaFil: Ferrara, Jonathan. Ministerio de Defensa. Secretaria de Planeamiento. Servicio Meteorológico Nacional; ArgentinaFil: D'elia, Raul Luis. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Unidad de Investigación y Desarrollo Estratégico para la Defensa. Ministerio de Defensa. Unidad de Investigación y Desarrollo Estratégico para la Defensa; ArgentinaFil: Antuña Sánchez, Juan Carlos. Universidad de Valladolid; EspañaFil: Cachorro Revilla, Victoria Eugenia. Universidad de Valladolid; EspañaFil: Calle, Abel. Universidad de Valladolid; EspañaFil: de Frutos Baraja, Ángel Máximo. Universidad de Valladolid; Españ

Evaluation of night-time aerosols measurements and lunar irradiance models in the frame of the first multi-instrument nocturnal intercomparison campaign

The first multi-instrument nocturnal aerosol optical depth (AOD) intercomparison campaign was held at the high-mountain Izaña Observatory (Tenerife, Spain) in June 2017, involving 2-min synchronous measurements from two different types of lunar photometers (Cimel CE318-T and Moon Precision Filter Radiometer, LunarPFR) and one stellar photometer. The Robotic Lunar Observatory (ROLO) model developed by the U.S. Geological Survey (USGS) was compared with the open-access ROLO Implementation for Moon photometry Observation (RIMO) model. Results showed rather small differences at Izaña over a 2-month time period covering June and July, 2017 (±0.01 in terms of AOD calculated by means of a day/night/day coherence test analysis and ± 2% in terms of lunar irradiance). The RIMO model has been used in this field campaign to retrieve AOD from lunar photometric measurements. No evidence of significant differences with the Moon's phase angle was found when comparing raw signals of the six Cimel photometers involved in this field campaign. The raw signal comparison of the participating lunar photometers (Cimel and LunarPFR) performed at coincident wavelengths showed consistent measurements and AOD differences within their combined uncertainties at 870 nm and 675 nm. Slightly larger AOD deviations were observed at 500 nm, pointing to some unexpected instrumental variations during the measurement period. Lunar irradiances retrieved using RIMO for phase angles varying between 0° and 75° (full Moon to near quarter Moon) were compared to the irradiance variations retrieved by Cimel and LunarPFR photometers. Our results showed a relative agreement within ± 3.5% between the RIMO model and the photometer-based lunar irradiances. The AOD retrieved by performing a Langley-plot calibration each night showed a remarkable agreement (better than 0.01) between the lunar photometers. However, when applying the Lunar-Langley calibration using RIMO, AOD differences of up to 0.015 (0.040 for 500 nm) were found, with differences increasing with the Moon's phase angle. These differences are thought to be partly due to the uncertainties in the irradiance models, as well as instrumental deficiencies yet to be fully understood. High AOD variability in stellar measurements was detected during the campaign. Nevertheless, the observed AOD differences in the Cimel/stellar comparison were within the expected combined uncertainties of these two photometric techniques. Our results indicate that lunar photometry is a more reliable technique, especially for low aerosol loading conditions. The uncertainty analysis performed in this paper shows that the combined standard AOD uncertainty in lunar photometry is dependent on the calibration technique (up to 0.014 for Langley-plot with illumination-based correction, 0.012–0.022 for Lunar-Langley calibration, and up to 0.1 for the Sun-Moon Gain Factor method). This analysis also corroborates that the uncertainty of the lunar irradiance model used for AOD calculation is within the 5–10% expected range. This campaign has allowed us to quantify the important technical difficulties that still exist when routinely monitoring aerosol optical properties at night-time. The small AOD differences observed between the three types of photometers involved in the campaign are only detectable under pristine sky conditions such as those found in this field campaign. Longer campaigns are necessary to understand the observed discrepancies between instruments as well as to provide more conclusive results about the uncertainty involved in the lunar irradiance models.This work has been developed within the framework of the activities of the World Meteorological Organization (WMO) Commission for Instruments and Methods of Observations (CIMO) Izaña Testbed for Aerosols and Water Vapour Remote Sensing Instruments. AERONET sun photometers at Izaña have been calibrated within the AERONET Europe TNA, supported by the European Union’s Horizon 2020 research and innovation program under grant agreement no. 654109 (ACTRIS‒2). CE318-T linearity check has been performed as part of the ESA-funded project “Lunar spectral irradiance measurement and modelling for absolute calibration of EO optical sensors” under ESA contract number: 4000121576/17/NL/AF/hh. LunarPFR has been performing measurements since 2014 in Norway thanks to Svalbard Science Forum funded project, 2014–2016. The authors would like to thank AERONET team for their support and also to NASA’s Navigation and Ancillary Information Facility (NAIF) at the Jet Propulsion Laboratory to help the implementation of the “SPICE” ancillary information system used in this study. We also thank Izaña's ITs for their work to implement the RIMO model in the free-access server. Special thanks should be given to Tom Stone, who has kindly provided us with the USGS/ROLO irradiance values used in the model comparison analysis. This work has also received funding from the European Union’s Horizon 2020 research and innovation programme and from Marie Skłodowska-Curie Individual Fellowships (IF) ACE-GFAT (grant agreement no. 659398). The authors are grateful to Spanish MINECO (CTM2015-66742-R) and Junta de Castilla y León (VA100P17)

Solar Radiation Climatology in Camagüey, Cuba (1981–2016)

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

Retrieval of aerosol properties using relative radiance measurements from an all-sky camera

International audienceThis 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

ALINE/LALINET Network Status

The Latin American Lidar Network, ALINE a.k.a LALINET is a federation lidar network established in 2008 which became a member of GALION/GAW program in 2013. Currently the network consists of 9 operational stations with the perspective of two more stations to be included. The network today covers more than 18 million Km2 and spans in latitude from -52° to 21° and in longitude from -78° to -47°. It should cover a larger area in the future as planned with the inclusion of more active stations

ALINE/LALINET Network Status

The Latin American Lidar Network, ALINE a.k.a LALINET is a federation lidar network established in 2008 which became a member of GALION/GAW program in 2013. Currently the network consists of 9 operational stations with the perspective of two more stations to be included. The network today covers more than 18 million Km2 and spans in latitude from -52° to 21° and in longitude from -78° to -47°. It should cover a larger area in the future as planned with the inclusion of more active stations

Latin American Lidar Network (LALINET): a diagnostic on networking instrumentation

LALINET (Latin American Lidar Network), previously known as ALINE, is the first fully operative lidar network for aerosol research in South America, probing the atmosphere on regular basis since September 2013. The general purpose of this network is to attempt to fill the gap in the knowledge on aerosol vertical distribution over South America and its direct and indirect impact on weather and climate by the establishment of a vertically-resolved dataset of aerosol properties. Similarly to other lidar research networks, most of the LALINET instruments are not commercially produced and, consequently, configurations, capabilities and derived-products can be remarkably different among stations. It is a fact that such un-biased 4D dataset calls for a strict standardization from the instrumental and data processing point of view. This study has been envisaged to investigate the ongoing network configurations with the aim of highlighting the instrumental strengths and weaknesses of LALINET.Fil: Guerrero Rascado, Juan Luis. Instituto de Pesquisas Energéticas e Nucleares; Brasil. Instituto Interuniversitario de Investigación del Sistema Tierra en Andalucía; España. Universidad de Granada; EspañaFil: Landulfo, Eduardo. Instituto de Pesquisas Energéticas e Nucleares; BrasilFil: Antuña, Juan Carlos. Instituto de Meteorología de Cuba; CubaFil: Barbosa, Henrique de Melo Jorge. Universidade de Sao Paulo; BrasilFil: Barja, Boris. Instituto de Meteorología de Cuba; Cuba. Universidade de Sao Paulo; BrasilFil: Bastidas, Álvaro Efrain. Universidad Nacional de Colombia; ColombiaFil: Bedoya, Andrés Esteban. Universidad Nacional de Colombia; ColombiaFil: da Costa, Renata Facundes. Instituto de Pesquisas Energéticas e Nucleares; BrasilFil: Estevan, René. Instituto de Meteorología de Cuba; CubaFil: Forno, Ricardo. Universidad Mayor de San Andrés; BoliviaFil: Gouveia, Diego Alvés. Universidade de Sao Paulo; BrasilFil: Jiménez, Cristofer. Universidad de Concepción; ChileFil: Larroza, Eliane Gonçalves. Instituto de Pesquisas Energéticas e Nucleares; BrasilFil: da Silva Lopes, Fábio Juliano. Instituto de Pesquisas Energéticas e Nucleares; Brasil. Universidade de Sao Paulo; BrasilFil: Montilla Rosero, Elena. Universidad de Concepción; ChileFil: de Arruda Moreira, Gregori. Instituto de Pesquisas Energéticas e Nucleares; BrasilFil: Nakaema, Walker Morinobu. Instituto de Pesquisas Energéticas e Nucleares; BrasilFil: Nisperuza, Daniel. Universidad Nacional de Colombia; ColombiaFil: Alegria, Dairo. Universidad Nacional de Colombia; ColombiaFil: Múnera, Mauricio. Universidad Nacional de Colombia; ColombiaFil: Otero, Lidia Ana. k División Lidar, CEILAP (UNIDEF-CONICET); ArgentinaFil: Papandrea, Sebastián Daniel. Consejo Nacional de Investigaciones Científicas y Técnicas. Instituto de Investigaciones Científicas y Técnicas para la Defensa. Centro de Investigación en Láseres y Aplicaciones; ArgentinaFil: Pallota, Juan Vicente. Consejo Nacional de Investigaciones Científicas y Técnicas. Instituto de Investigaciones Científicas y Técnicas para la Defensa. Centro de Investigación en Láseres y Aplicaciones; ArgentinaFil: Pawelko, Ezequiel Eduardo. Consejo Nacional de Investigaciones Científicas y Técnicas. Instituto de Investigaciones Científicas y Técnicas para la Defensa. Centro de Investigación en Láseres y Aplicaciones; ArgentinaFil: Quel, Eduardo Jaime. Consejo Nacional de Investigaciones Científicas y Técnicas. Instituto de Investigaciones Científicas y Técnicas para la Defensa. Centro de Investigación en Láseres y Aplicaciones; ArgentinaFil: Ristori, Pablo Roberto. Consejo Nacional de Investigaciones Científicas y Técnicas. Instituto de Investigaciones Científicas y Técnicas para la Defensa. Centro de Investigación en Láseres y Aplicaciones; ArgentinaFil: Rodrigues, Patricia Ferrini. Instituto de Pesquisas Energéticas e Nucleares; BrasilFil: Salvador, Jacobo Omar. Consejo Nacional de Investigaciones Científicas y Técnicas. Instituto de Investigaciones Científicas y Técnicas para la Defensa. Centro de Investigación en Láseres y Aplicaciones; ArgentinaFil: Sánchez, Maria Fernanda. Universidad Mayor de San Andrés; BoliviaFil: Silva, Antonieta. Universidad de Concepción; Chile. Universidad de La Frontera; Chil