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Solar Elevation (solar + elevation)

Distribution by Scientific Domains

Life Sciences	85%

Selected Abstracts

A ,polarisation sun-dial' dictates the optimal time of day for dispersal by flying aquatic insects

FRESHWATER BIOLOGY, Issue 7 2006
ZOLTÁN CSABAI
Summary 1. Daily changes in the flight activity of aquatic insects have been investigated in only a few water beetles and bugs. The diel flight periodicity of aquatic insects and the environmental factors governing it are poorly understood. 2. We found that primary aquatic insects belonging to 99 taxa (78 Coleoptera, 21 Heteroptera) fly predominantly in mid-morning, and/or around noon and/or at nightfall. There appears to be at least four different types of diurnal flight activity rhythm in aquatic insects, characterised by peak(s): (i) in mid-morning; (ii) in the evening; (iii) both in mid-morning and the evening; (iv) around noon and again in the evening. These activity maxima are quite general and cannot be explained exclusively by daily fluctuations of air temperature, humidity, wind speed and risks of predation, which are all somewhat stochastic. 3. We found experimental evidence that the proportion (%) P(,) of reflecting surfaces detectable polarotactically as ,water' is always maximal at the lowest (dawn and dusk) and highest (noon) angles of solar elevation (,) for dark reflectors while P(,) is maximal at dawn and dusk (low solar elevations) for bright reflectors under clear or partly cloudy skies. 4. From the temporal coincidence between peaks in the diel flight activity of primary aquatic insects and the polarotactic detectability P(,) of water surfaces we conclude that the optimal times of day for aquatic insects to disperse are the periods of low and high solar elevations ,. The , -dependent reflection,polarisation patterns, combined with an appropriate air temperature, clearly explain why polarotactic aquatic insects disperse to new habitats in mid-morning, and/or around noon and/or at dusk. We call this phenomenon the ,polarisation sun-dial' of dispersing aquatic insects. [source]

UV Exposition During Typical Lifestyle Behavior in an Urban Environment

PHOTOCHEMISTRY & PHOTOBIOLOGY, Issue 3 2010
Alois W. Schmalwieser
In this study the personal exposure to solar UV radiation in an urban environment was measured. Lifestyle in an urban environment is characterized by staying indoors during most of the day. Furthermore, the ambient UV radiation is mitigated by shadowing by buildings. The aim of the study was to find out activities which may contribute to UV-induced health risk in a low exposure environment. Exposure was measured during typical outdoor activities: shopping, walking, sitting in a sidewalk café, cycling, sightseeing and at an open-air pool (solar elevation: 10°,70°). Measurements were taken with an optoelectronic device which was fixed on the chest. Besides the UV Index we used the sun burn time (SBT) for risk assessments. Generalization of our results was made by calculating ratios of personal exposure to the ambient UV radiation. UV exposure was by far the highest when our study subject stayed at the swimming pool. The SBT was around 30 min for melano-compromised skin type. For all other activities, except shopping, the SBT range up to 1 h. With respect to photodamage we found that at high solar elevation (>45°) photoprotective measures should be applied for certain activities even within a city. [source]

Standard Ultraviolet Daylight for Nonextreme Exposure Conditions,

PHOTOCHEMISTRY & PHOTOBIOLOGY, Issue 4 2005
François J. Christiaens
ABSTRACT The skin is exposed to ultraviolet radiation (UVR) from natural or artificial sources on a daily basis. The effects of chronic low dose exposure merit investigation, even when these effects are neither conspicuous nor clinically assessable. The purpose of the present study was to define a relative spectral UV irradiance that is representative of frequent nonextreme sun exposure conditions and therefore more appropriate for studies of the long-term and daily effects of solar UV on the skin. Solar spectral UV irradiance values were calculated for different dates and locations by using a radiative transfer model. The spectral irradiance values obtained when the solar elevation is lower than 45° were averaged. An important feature is the dUVA (320,400 nm) to dUVB (290,320 nm) irradiance values ratio, which was found to be 27.3 for the overall average. When the months corresponding to extreme irradiance values (low or high) were excluded from the calculations, the dUVA to dUVB ratio ranged from 27.2 to 27.5. The mean spectral irradiance of the model presented here represents environmental UV exposure conditions and can be used both as a standard to investigate the biological effects of a nonextreme UVR and to assess the effectiveness of products for daily skin protection. [source]

European Solar Telescope: Progress status

ASTRONOMISCHE NACHRICHTEN, Issue 6 2010
M. Collados
Abstract In this paper, the present status of the development of the design of the European Solar Telescope is described. The telescope is devised to have the best possible angular resolution and polarimetric performance, maximizing the throughput of the whole system. To that aim, adaptive optics and multi-conjugate adaptive optics are integrated in the optical path. The system will have the possibility to correct for the diurnal variation of the distance to the turbulence layers, by using several deformable mirrors, conjugated at different heights. The present optical design of the telescope distributes the optical elements along the optical path in such a way that the instrumental polarization induced by the telescope is minimized and independent of the solar elevation and azimuth. This property represents a large advantage for polarimetric measurements. The ensemble of instruments that are planned is also presented (© 2010 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source]