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- Are SQM-L measurements polarization dependent?Publication . Bará, Salvador; C. Lima, RaúlSeveral observers informed that slightly different SQM-L zenithal brightness readings can be obtained depending on the azimuthal orientation of the device. Since the light scattered by the atmosphere generally has some degree of polarization, depending on the relative position of the source, the observation direction, the light spectrum, and the atmospheric molecular and aerosol constituents, we wanted to check whether the measurements made with these devices show any intrinsic dependence on the polarization of the incoming light. Although the SQM detectors do not purposely include any polarizing optical element, some polarization dependent effects could potentially arise from the presence of anisotropic materials (e.g. some kinds of plastics) producing differential Fresnel losses in the orthogonal vibration components of the incoming field.
- The Alqueva hydro-meteorologic experimentPublication . Salgado, R.; Potes, M.; Albino, A.; Apolinário, J.; Barbosa, S.; Bárias, S.; Beliche, P.; Bortoli, D.; Canhoto, P.; Costa, M. J.; Fernandes, R.M.; Harrison, G. G.; Ilhéu, A.; Le Moigne, P.; Lima, Raúl; Lopes, F.; Lopes, T.; Marques, J.; Melgão, M.; Miranda, P. M.; Morais, M.; Murteira, M.; Nicoll, K.; Novais, M. H.; Nunes, S.; Parrondo, M. C.; Penha, A.; Pereira, S.; Policarpo, C.; Prior, V.; Rodrigues, C. M.; Rosado, J.; Sá, A.; Serafim, A.; Silva, H.; Soares, P. M. M.; Tlemçani, M.; Zavattieri, A.The ALqueva hydro-meteorological experiment, ALEX 2014 (http://www.alex2014.cge.uevora.pt) was an integrated field campaign with measurements of chemical, physical and biological parameters at different experimental sites in the Alqueva reservoir and in its surrounding region. With the main purpose of studing the lake-atmosphere interactions, the ALEX 2014 took place form June to September and comprised a three days Intensive Observation Period (IOP) from 22 to 24 July.
- A call for scientists to halt the spoiling of the night sky with artificial light and satellitesPublication . Falchi, Fabio; Bará, Salvador; Cinzano, Pierantonio; Lima, Raúl C.; Pawley, MartinUnfettered access to dark night skies is rapidly diminishing, due to light pollution and satellite constellation tracks. Scientists should do more to stand up to ‘big light’ and ‘big space’ and preserve this natural resource.
- Can we illuminate our cities and (still) see the stars?Publication . Bará, Salvador; Falchi, Fábio; C Lima, Raúl; Pawley, MartinCould we enjoy starry skies in our cities again? Arguably yes. The actual number of visible stars will depend, among other factors, on the spatial density of the overall city light emissions. In this paper it is shown that reasonably dark skies could be achieved in urban settings, even at the center of large metropolitan areas, if the light emissions are kept within admissible levels and direct glare from the light sources is avoided. These results may support the adoption of science-informed, democratic public decisions on the use of light in our municipalities, with the goal of recovering the possibility of contemplating the night sky everywhere in our planet.
- Ilumina o teu relógio - De que forma o teu corpo sabe as horasPublication . Weinzaepflen, Coline; Spitschan, Manuel; Pinto, Joana; Lima, Raul Cerveira
- Interobserver variability of hand-held SQM-L measurements.Publication . Bará, Salvador; C. Lima, Raúl; Arós, Ángel R.; Giráldez, LucíaUnder stable luminance conditions the uncertainty of the brightness measurements obtained with hand-held SQM-L detectors arises from the combination of their intrinsic precision and the random pointing errors incurred by the observers. Based on the observations performed by 13 independent observers without previous training in SQM-L use, we got an estimate of 0.074 mag/arcsec 2 for the observer-induced uncertainty (standard deviation of the sample) under 20.83 mag/arcsec 2 skies.
- Relatório preliminar da iluminação da aldeia da Cumeada, Reguengos de Monsaraz e sugestões de melhoramento Parte II - Medição de iluminânciasPublication . Lima, Raul CerveiraApós uma primeira análise qualitativa da iluminação pública na aldeia da Cumeada (Reguengos de Monsaraz, Évora), efectuou-se uma análise das iluminâncias horizontais máximas a 1.5 m de altura em relação ao solo, simulando a iluminação que recebe um observador ao observar por um telescópio. A análise identificou iluminâncias excessivas para uma zona residencial e com fluxo rodoviário ou pedonal baixo ou muito baixo. Propõem-se nesta adenda ao relatório preliminar medidas de correcção no que respeita aos fluxos luminosos e ao tipo de fonte de luz por forma a melhorar a qualidade do céu nocturno, a qualidade ambiental e a qualidade de vida dos residentes.
- Interactions lake-atmosphere: the ALEX 2014 field campaign and numerical simulationsPublication . Salgado, R.; Potes, M.; Albino, A.; Apolinário, J.; Barbosa, S.; Bárias, S.; Beliche, P.; Bortoli, D.; Canhoto, P.; Costa, M. J.; Fernandes, R.M.; Harrison, G.; Ilhéu, A.; Le Moigne, P.; Lima, Raúl; Lopes, F.; Lopes, T.; Marques, J.; Melgão, M.; Miranda, P. M.; Morais, M.; Murteira, M.; Nicoll, K.; Novais, M. H.; Nunes, S.; Parrondo, M. C.; Penha, A.; Pereira, S.; Policarpo, C.; Prior, V.; Rodrigues, C. M.; Rosado, J.; Sá, A.; Serafim, A.; Silva, H.; Soares, P. M. M.; Tlemçani, M.; Zavattieri, A.The ALqueva hydro-meteorological EXperiment, ALEX 2014, was an integrated field campaign with measurements of chemical, physical and biological parameters in water and air at different experimental sites in the region of the Alqueva reservoir, a 250 km2 man made lake, in the southeast of Portugal. The Field campaign took place from June 1 to September 30, 2014 and comprises an Intensive Observation Period (IOP) of three days (22 to 24 July). During the four months, the over water fluxes of momentum, heat and mass (H2O and CO2) were obtained with an integrated Open-Path CO2 /H2O Gas Analyser and 3D Sonic Anemometer, mounted on a floating platform, where radiative fluxes were also measured, as well as the water temperature profile. Eight near surface weather stations were operating in the area and air quality, atmospheric electrical field (Potential Gradient) and radon (222Rn) concentration were continuous monitored. Along this period, in situ measurements, water samples and biological elements were monthly collected from three fixed platforms placed in the lacustrine zone and from selected sites in the margins. During the IOP, radiosondes were launched every tree hours, allowing a characterization of the atmospheric boundary layer and its evolution. In 10 occasions Geigersondes were coupled to the radiosondes in order to obtain the atmospheric ionization profile. The boundary layer was characterized with a Ceilometer and the vertical distribution of O3 and NO2 were obtained from a Spectrometer. A GPS network of 15 GNSS stations was installed in order to map the water vapour. The sky brightnesson the nights of July 24 and 25, was measured using a Sky Quality Meter. The lake-atmosphere interactions and its impact in the boundary layer structure and in the local circulations are studied using data collected during the ALEX 2014 POI together with results from numerical simulations performed with the non-hydrostatic Meso-NH french model.
- Quantifying the visual impact of wind farm lights on the nocturnal landscapePublication . Bará, Salvador; C. Lima, RaúlWind farm lights are a conspicuous feature in the nocturnal landscape. Their presence is a source of light pollution for residents and the environment, severely disrupting in some places the aesthetic, cultural, and scientific values of the pristine starry skies. In this work we present a simple model for quantifying the visual impact of individual wind turbine lights, based on the comparison of their brightness with the brightness of well- known night sky objects. The model includes atmospheric and visual variables, and for typical parameters it shows that medium-intensity turbine lights can be brighter than Venus up to ~4 km from the turbine, brighter than CMa (the brightest star on the nighttime sky) until about ~10 km, and reach the standard stellar visibility limit for the unaided eye (m v =+6.00) at ~38 km. These results suggest that the visual range of wind farms at nighttime may be significantly larger than at daytime, a factor that should be taken into account in environmental impact assessments.