Search results for "Radiació solar"
showing 10 items of 16 documents
Design of a sun tracker for the automatic measurement of spectral irradiance and construction of an irradiance database in the 330-1100 nm range
2007
Abstract An automatic global and direct solar spectral irradiance system has been designed based on two LICOR spectroradiometers equipped with fibre optics and remote cosine sensors. To measure direct irradiance a sun tracker based on step motors has been developed. The whole system is autonomous and works continuously. From the measurements provided by this system a spectral irradiance database in the 330–1100 nm range has been created. This database contains normal direct and global horizontal irradiances as well as diffuse irradiance on a horizontal plane, together with total atmospheric optical thickness and aerosol optical depth.
Column-integrated aerosol optical properties in Sodankylä (Finland) during the Solar Induced Fluorescence Experiment (SIFLEX-2002).
2006
[1] A study has been made of the column aerosols using solar irradiance extinction measurements at ground level in a boreal region (Sodankyla, Finland) during spring 2002. The aerosol properties have been related to air mass origin. In general, the aerosol levels were observed to be very low, independent of the air mass origin, with an aerosol optical depth (AOD) value at 500 nm of less than 0.09 ± 0.03. Two characteristic patterns were observed depending on whether the air masses originated in the north and west or from the south and east. In the first case (north and west origins) the aerosol load was very small, with very low optical depths in the range 0.03 ± 0.02 to 0.09 ± 0.03 for 500…
A new method for detemining the Angstrom turbidity coefficient from broad-band filter measurements.
2000
In this work, a new method for determining Ångström turbidity coefficients is presented. This method is based on broadband filter irradiance measurements. By combining measurements obtained with different filters it is possible to obtain a single value of the turbidity coefficient representative of the whole measurement range of the pyrheliometer. The results provided by this new method are compared with the original Ångström method and turbidity coefficient values derived by spectroradiometric measurements. The results reproduce the actual values, as measured by a spectroradiometer, better than the previous best correlation did, thus demonstrating the advantage of analyzing the optical thi…
Phenomenology of maximal and near-maximal lepton mixing
2000
We study the phenomenological consequences of maximal and near-maximal mixing of the electron neutrino with other ($x$=tau and/or muon) neutrinos. We describe the deviations from maximal mixing in terms of a parameter $\epsilon\equiv1-2\sin^2\theta_{ex}$ and quantify the present experimental status for $|\epsilon|<0.3$. We find that the global analysis of solar neutrino data allows maximal mixing with confidence level better than 99% for $10^{-8}$ eV$^2\lsim\Delta m^2\lsim2\times10^{-7}$ eV$^2$. In the mass ranges $\Delta m^2\gsim 1.5\times10^{-5}$ eV$^2$ and $4\times10^{-10}$ eV$^2\lsim\Delta m^2\lsim2\times10^{-7}$ eV$^2$ the full interval $|\epsilon|<0.3$ is allowed within 4$\sigma$(99.9…
Characterization of the atmosphere during SEN2FLEX 2005 field campaign
2008
The European Space Agency carried out the Sentinel-2 and Fluorescence Experiment (SEN2FLEX) campaign in Barrax (Spain) during the summer of 2005, with the main objective of observe solar induced fluorescence signal using the AirFLEX airborne instrument over different vegetation targets in order to verify signal suitability for observations from space as proposed in the FLEX mission. A highly precise atmospheric correction is mandatory for adequate measurements of the AirFLEX instrument; thus a complete characterization of the atmosphere was programmed in SEN2FLEX in order to document the presence of atmospheric aerosols above the experimental area, as their effects represent the major sourc…
Intercomparison of spectroradiometers for global and direct solar irradiance in the visible range.
2003
This paper presents the results of the analysis of the spectral, global, and direct solar irradiance measurements in the visible range (400–700 nm) that were made in the framework of the first Iberian UV–visible (VIS) instruments intercomparison. The instruments used in this spectral range were four spectroradiometers: three Licor 1800s equipped with different receiver optics and one Optronic 754. For the direct solar irradiance measurements the spectroradiometers were equipped with collimators with different fields of view. Parallel studies have been carried out with the data given by the spectroradiometers with their original calibration file and with the same data that is corrected, foll…
Algunas evidencias clínicas sobre la necesidad del calibrado de simuladores solares usados en dermatología
2001
Los simuladores solares emiten una radiación espectral que reproduce con bastante fidelidad el espectro de la radiación solar. Se emplean en dermatología, fundamentalmente en la realización del fototest para la determinación de dosis eritemáticas (MED). Su espectro de emisión puede variar con el tiempo en función del envejecimiento de las fuentes o por desajustes mecánicos u ópticos del sistema, lo que hace obligada una calibración periódica de los mismos. Esta calibración se realiza por medio de espectrorradiómetros de precisión, lo que permite comparar la respuesta espectral en mediciones sucesivas que deberían realizarse en función del tiempo de uso, al menos cada 6 meses. En este trabaj…
Influencia de la temperatura en las medidas de irradiancia espectral
2006
Las técnicas radiométricas se han empleado durante muchos años para obtener propiedades ópticas de los aerosoles en la columna atmosférica. Habitualmente los espectrorradiómetros y fotómetros permanecen en el exterior, sobre seguidores automáticos, que permiten la medida de la radiación solar directa a lo largo de todo el día. Estos instrumentos se ven afectados por la temperatura ambiente, por lo que es preciso determinar su efecto para corregir las medidas de irradiancia. For many years the radiometric techniques have been widely applied for retrieving several aerosol optical properties in the atmospheric column. Usually the spectroradiometers are deployed outdoors on automatic sun tracki…
A new approach for characterizing atmospheric aerosols from spectral values of their optical depth. A simulated case study.
2005
We are developing a new method to determine the spectral contribution to the aerosol optical depth due to each aerosol type. An aerosol type depends directly on the procedence of the particles (marine, continental, artic, etc) and it is formed by some different pure components (mineral, soot, soluble and insoluble particles, sulphate, etc). In order to separate these contributions it is necessary to have the spectral aerosol optical thickness and aerosol size distribution. We use this distribution function to identify the different components of aerosols allowing us to reconstruct the aerosol optical depth taking into account the contribution of each type of aerosol. The validation of the m…
Solar Neutrinos
2012
The study of solar neutrinos has given a fundamental contribution both to astroparticle and to elementary particle physics, offering an ideal test of solar models and offering at the same time relevant indications on the fundamental interactions among particles. After reviewing the striking results of the last two decades, which were determinant to solve the long standing solar neutrino puzzle and refine the Standard Solar Model, we focus our attention on the more recent results in this field and on the experiments presently running or planned for the near future. The main focus at the moment is to improve the knowledge of the mass and mixing pattern and especially to study in detail the lo…