A simple and inexpensive fully automated all-sky imaging system based on a commercial digital camera with a fish-eye lens and a rotating polarizer is presented. The system is characterized and two examples of applications in atmospheric physics are given: polarization maps and cloud detection. All-sky polarization maps are obtained by acquiring images at different polarizer angles and computing Stokes vectors. The polarization in the principal plane, a vertical cut through the sky containing the Sun, is compared to measurements of a well-characterized spectroradiometer with polarized radiance optics to validate the method. The images are further used for automated cloud detection using a simple color-ratio algorithm. The resulting cloud cover is validated against synoptic cloud observations. A Sun coverage parameter is introduced that shows, in combination with the total cloud cover, useful correlation with UV irradiance.

Purpose -The purpose of this research paper is to prove the superiority of a two-stage data envelopment analysis compared to a one-stage approach in measuring a football club's efficiency. Moreover it provides best practice benchmarks for the research sample which supports football officials to orient themselves to the right clubs. Design/methodology/approach -A non-parametric two-stage data envelopment analysis for the seasons 2006/07 to 2008/09 is introduced to measure the efficiency of English Premier League football clubs from an off-field and an on-field perspective. The results are compared with those of the traditional one-stage data envelopment analysis approach to identify insufficiencies of the latter. Findings -The results show evidence that different conclusions derive from either the one-or the twostage approach with the threat of potential misinterpretations in the case of the former. Furthermore, this study provides football clubs with information to focus on specific efficiency-enhancing strategies at the individual stages of the production process and therefore acts as a supportive tool for the football club officials for setting corrective actions if inefficiencies are identified.Research limitations/implications -The present article provides a foundation for future studies in other football leagues as well as for an intertemporal analysis which evaluates the efficiency of a club on a yearly basis. Originality/value -This is the first paper that introduces a two-stage data envelopment analysis approach in football research. It has proven that it can identify sources of inefficiencies more accurately than a one-stage data envelopment analysis and provides football officials with valuable information about their club.

Presented here are the results of a short but intense measurement campaign at Lauder, New Zealand, in which spectral irradiance from instruments operated by the National Institute of Water and Atmospheric Research (NIWA) and Austria/Innsbruck (ATI) were traced to different irradiance standards and compared. The observed spectral differences for global irradiance were relatively small (Ͻ5%) and were consistent with those expected from observed differences in the radiation standards used by each group. Actinic fluxes measured by both groups were also intercompared and found to agree at the 10% level. The ATI instrument had the additional capability of measuring solar direct beam irradiance and sky radiances. These provided the first series of sky radiance measurements at this pristine Network for the Detection of Atmospheric Composition Change (NDACC) site. The polarization of sky radiance results were compared with estimates from a radiative transfer model without any aerosols and was found to be up to 25% smaller. Total ozone values derived from Total Ozone Mapping Spectrometer (TOMS), Dobson measurements by NIWA, spectral direct sun measurements by ATI, and spectral global irradiance measurements by NIWA agreed generally within 2%-3%.

The ultraviolet‐A (UVA) part of the solar spectrum at the Earth's surface is an essential environmental factor but continuous long‐time monitoring of UVA radiation is rarely done. In Austria, three existing stations of the UV monitoring network have been upgraded with UVA broadband instruments. At each station, one instrument measures global UVA irradiance and—in parallel—a second instrument measures diffuse irradiance. Recent and past measurements are available via a web page. This paper describes the used instruments, calibration and quality assurance and control procedures. Global and diffuse UVA measurements during a period of up to 5 years are presented. Data indicate clear annual courses and an increase of UVA with altitude by 8–9% per 1000 m. In the first half of the year, UVA radiation is higher than in the second half, due to less cloudiness. In Vienna (153 m asl), the mean daily global UVA radiant exposure in summer is almost as high as at Mt. Gerlitzen (1540 m asl), equalizing the altitude effect, due to less cloudiness. However, in winter, the UVA radiant exposure at Mt. Gerlitzen is double as high, as in Vienna.

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