Search results for "IRRADIANCE"
showing 10 items of 152 documents
Analysis of the irradiance along different paths in the image space using the Wigner distribution function
1997
Abstract The intensity distribution along different paths in the image space of an optical system is described in a two-dimensional phase-space domain in terms of the Wigner distribution function. This approach is useful for an efficient analysis of the performance of optical imaging systems suffering from spherical aberration. The good performance of the method is shown in some numerical simulations.
Impact of Crystal Habit on Cirrus Radiative Properties
2007
The impact of assumed ice crystal morphology of subtropical cirrus on the solar and thermal infrared (IR) radiative field above, within, and below the cirrus is quantified. For this purpose airborne measurements of ice crystal size distribution from the CRYSTAL-FACE campaign and a library of optical properties of nonspherical ice crystal habits are implemented into radiative transfer simulations.Two cirrus cases are studied in detail: a high (cold) cirrus cloud with small visible optical thickness (τ≈1), and a lower (warmer) cirrus cloud of relatively large visible optical thickness (τ≈7). For t+he solar wavelength range the impact of shape characteristics of the crystals was important for …
A comparative study of SPCTRAL2 and SMARTS2 parameterised models based on spectral irradiance measurements at Valencia, Spain
1998
Abstract Results obtained using the parametric models SPCTRAL2 and SMARTS2 for the urban area of Valencia, Spain, have been analysed and compared with experimental measurements at ground level obtained with two Li-cor 1800 spectroradiometers with a 6 nm resolution. The study used two different input parameters in both models for the aerosol characterisation: the aerosol optical thickness at 0.5 μ m, τ a λ (0.5) , and the Angstrom turbidity coefficient β . The results obtained show that both algorithms reproduce quite correctly the spectral irradiance experimental values when an urban aerosol model parameterised by the τ a λ (0.5) value is considered. In all the cases the deviations are low…
Measurements of integrated direct, diffuse and global ultraviolet-B radiation
2015
Abstract We present the first multiyear set of simultaneous measurements of the global ultraviolet-B radiation and its two components: direct and diffuse. The measurements have been taken with four YES-UVB-1 radiometers: two radiometers to measure the diffuse radiation, one provided with a shadow band and the other with a shadow disk on a Sun tracker; a radiometer to measure the global horizontal radiation; and a Sun-tracking radiometer to measure the direct radiation with an especially designed radiance collimator. The diffuse minute-values measured with both instruments agree within a coefficient correlation of 1.00. The diffuse component represents at least 50% of the global UVB (ultravi…
A study of extreme overirradiance events for solar energy applications using NASA’s I3RC Monte Carlo radiative transfer model
2015
Abstract Near the Equator, some cloud types can boost the terrestrial solar irradiance to above 1.8 kW/m2. Even at high latitude close to 60°N, we have measured bursts up to 1.6 kW/m2, almost at sea level. For comparison, the extraterrestrial irradiance peaks at about 1.4 kW/m2 in early January. The global upper limit for extreme overirradiance is still unknown. The enhancement is strongest within about 3° from the unobstructed solar disk. We use the NASA’s I3RC Monte Carlo model to simulate the radiative transfer of solar photons in a cloudy atmosphere. The geometry includes an overhead sun and an infinite plane parallel water cloud with a ‘circular’ gap of the same angular diameter as tha…
Talbot array illuminators with binary phase gratings
2009
We establish that, in six different cases, binary phase gratings can be applied to implement Talbot array illuminators. Three of the six cases are reported for what is to our knowledge the first time.
Uniqueness verification of blue fraction as a parameter of spectral irradiance quantification
2021
The spectral distribution of global irradiance is measured in the optimal tilt (45° south) plane of array for the calender year 2020 in Grimstad, Norway. In this work the spectral distribution is quantified in terms of the Blue Fraction (BF). The uniqueness of BF has been tested and reported using the same methodology used for uniqueness verification of average photon energy (APE). The results show that the coefficient of correlation between the APE and BF was 0.98, meaning a possible bijective relation between these two parameters whereby both indicate a similar spectrum. The percentage contribution of integrated irradiance (Rc) was calculated for 25 nm wavelength bins for the BF region 35…
Relative efficiency revealed: Equations for k<inf>1</inf>&#x2013;k<inf>6</inf> of the PVGIS model
2014
The European PV Geographical Information System (PVGIS) describes module performance in terms of the relative efficiency with respect to Standard Testing Conditions (STC). The efficiency's dependence on irradiance and operating temperature is modeled with a bi-quadratic polynomial with respect to the relative temperature and the logarithm of relative irradiance. In earlier works, the present author derived relations between two model coefficients describing the irradiance dependence at 25°C, k 1 and k 2 , and I–V curve model parameters such as the series resistance RS and the ideality factor n. There was good agreement between the theoretical and fitted values of k 1 , but the fitted values…
UV Index Experimental Values During the Years 2000 and 2001 from the Spanish Broadband UV-B Radiometric Network¶
2007
An analysis is made of experimental ultraviolet erythemal solar radiation data measured during the years 2000 and 2001 by the Spanish UV-B radiation evaluation and prediction network. This network consists of 16 Robertson-Berger type pyranometers for evaluating solar erythemal radiation and five Brewer spectroradiometers for evaluating the stratospheric ozone. On the basis of these data the Ultraviolet Index (UVI) was evaluated for the measuring stations that are located either in coastal regions or in the more densely populated regions inland on the Iberian Peninsula. It has been checked that in most cases the maximum irradiance values corresponded to solar noon, although there were except…
Measurement and analysis of broadband UVB solar radiation in Spain.
2012
Measurements of broadband UVB irradiance (290-315 nm) at 14 locations in Spain for the period 2000-2009 have been used to generate instantaneous, hourly and daily values of irradiance (W m(-2)) and radiant exposure (kJ m(-2)). These measurements, and its statistical indices, have been analyzed. For the UVB irradiance, the values corresponding to July (maximum) and December (minimum) have been analyzed as representative of the year during the whole period for all locations. For the UVB radiant exposure, the temporal evolution of daily values has been evaluated for all locations to estimate an average yearly behavior. The accumulated radiant exposure for an average year has also been studied …