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Photosynthetically active radiation (PAR) is a critical component driving the photosynthetic processes of plants. The content of global solar radiation (Rs) in PAR wavelengths, expressed as the PAR/Rs ratio, is an important attribute in meteorological and biological studies. Especially in the urban environment, which is affected by pollutants, urban materials, and elements, the solar radiation fluxes and their relations are highly influenced. In the present study, PAR/Rs is investigated in the Mediterranean urban environment of Attica, Greece. The temporal variation of the hourly ratio values is assessed in conjunction with several meteorological factors. The results indicate an annual PAR/Rs average value of 0.385 (SD = 0.039), with rather constant seasonal and monthly values and small variability, possibly attributed to the urban microclimate with small variability. Atmospheric clearness index and optical thickness were the most influential factors for the formation of the radiation ratio, which is also affected, to a lesser degree, by temperature, humidity, and related attributes. Aerosols, especially O3, NO2, and CO, also have impacts on the radiation ratio due to their preferred radiation absorbance at specific wavelengths. The results suggest important differences with similar studies in forest areas, underscoring the need for expanding the study in urban green areas, especially in Mediterranean cities. [ABSTRACT FROM AUTHOR]

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The directional variation in upwelling thermal radiance (referred to as “thermal anisotropy”) is one of the important issues in retrieving representative urban land surface temperature (LST) from remote sensing data. Yet, there is a gap between urban thermal anisotropy assessed from different observational and modeling approaches at different time scales. Thermal anisotropy at the satellite observing scale (~1 km) is usually derived from multiangular thermal observations that are a result of temporal aggregation over long time series. How well this type of anisotropy estimate represents the instantaneous thermal anisotropy (e.g., from airborne and some modeling techniques) at the satellite scale remains unclear. To close this knowledge gap, we comprehensively compare Moderate-Resolution Imaging Spectroradiometer (MODIS)-derived anisotropy and quasi-simultaneous airborne observations in urban areas and assess the factors that control anisotropic features of LST at seasonal and diurnal scales. Furthermore, we use model simulations to separately assess the impacts of 1) weather variability on anisotropy and 2) solar angle variation on zenithal variation in anisotropy, both of which have been largely simplified in the MODIS-derived approach. The instantaneous model-derived or airborne-measured anisotropy in early morning (~10:00) and late afternoon (~14:00) is closer to the seasonally aggregated MODIS-derived anisotropy from Terra-Day (with a median overpass time of 11:00) and Aqua-Day (13:00), respectively, whereas it has a good representation during winter. The investigation of the diurnal and seasonal characteristic of MODIS-derived anisotropy is a critical step needed to understand its performance for global urban thermal anisotropy profiles. [ABSTRACT FROM AUTHOR]

Copyright of Studia Mythologica Slavica is the property of Scientific Research Centre of Slovenian Academy of Sciences & Arts and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

The purpose of designing a spacecraft Altitude and dynamic control models play an important role in an interplanetary space mission. Particular emphasis is controlling spacecraft Altitude by sail tilting and shifting. In addition, investigate an uncertain balance amongst the centre of pressure and centre of mass on a single axis gimbaled control. Implies a method of Monte Carlo is with standing a significant of solar pressure disturbance torque in deep space mission. A flight test experiment drives in a Low Earth Orbit (LEO), hence, authenticate the source of solar sailing is also suggested. Parameters are incorporating to study and demonstrate the various principals and methods involved in altitude control design and dynamic modeling at LEO. Mitigation of disturbance torques was also examined. [ABSTRACT FROM AUTHOR]

The Moon, Earth's only natural satellite, is a potential new platform for Earth observation. Moreover, with the wide applicability of the angular information from remote sensing data, it has been attracting increasingly more attention. Accordingly, this study focuses on the angular characteristics of Moon-based Earth observations. Using ephemeris DE430 and Earth orientation parameters, the position and attitude of the Sun, Earth, and Moon were obtained and their coordinates normalized to a single framework using coordinate transformations between the related reference systems. Then, an angular geometric model of Moon-based Earth observations was constructed, and the corresponding angular algorithms were presented. The results revealed the angular range and distribution characteristics of Moon-based Earth observations. For every point on the surface of the Earth, the view and solar zenith angles all vary widely, which decreases with increasing latitude. The view and solar zenith angles all vary widely with the largest range of values in the equatorial and polar regions and a smaller range of values in mid-latitudes. Furthermore, the range of solar angles of Moon-based Earth observations is the same as that of all-time solar angles, indicating the potential for monitoring and understanding large-scale geoscientific phenomena using Moon-based Earth observations. [ABSTRACT FROM AUTHOR]

A number of interconnected scholarly publications discussing the phenomenon of the so-called sacred triangles have appeared lately. The authors who believe in the existence of this phenomenon argue that such triangles are based on a precisely determined value of the obliquity of the ecliptic. However, a detailed analysis of some of the key tenets discussed in their publications has revealed the gratuitous nature of this hypothesis, as well as its fundamentally unscientifc character and the methodological faws inherent in its overall development. Especially worrying is the falling into the pitfall of circular argumentation (circulus vitiosus) by the authors adhering to this hypothesis, their avoidance of any dialogue with relevant scholarly literature and their questionable understanding of fundamental phenomena upon which their hypothesis is built. A glaring example of the lattermost is the misunderstanding of the obliquity of the ecliptic on the part of the adherents of the so-called sacred triangles hypothesis. [ABSTRACT FROM AUTHOR]

Photosynthetically active radiation use efficiency (PARUE) of orchardgrass ( Dactylis glomerata L.) and tall fescue ( Schedonorus phoenix (Scop.) Holub) was determined. Leaf mass was harvested for canopies at different shade levels when each reached 20 cm height with 5 cm residue for regrowth to simulate grazing. Total incident PAR at each site was summed for the growth period (S-PAR). Values for PARUE were calculated from dried leaf mass divided by S-PAR. The more highly shaded plants reached 20 cm at lower S-PAR. While overall leaf mass decreased linearly with shade induced decreases in S-PAR, PARUE increased exponentially. The coefficients for the equations representing this exponential increase vary for forage species and may represent a useful index for characterizing forage response to silvopastoral systems. [ABSTRACT FROM AUTHOR]