Home About us Contact
|
Home About us Contact | ||
|
|
||
Solar Irradiance (solar + irradiance)
Selected AbstractsPhysiological Responses of Acropora cervicornis to Increased Solar Irradiance,PHOTOCHEMISTRY & PHOTOBIOLOGY, Issue 4 2007Juan L. Torres ABSTRACT The effects of increased UV radiation (UV-B [280,320 nm] + UV-A [320,400 nm]; hereafter UVR) on the growth, production of photosynthetic pigments and photoprotective mycosporine-like amino acids (MAAs) were studied in the threatened Caribbean coral Acropora cervicornis transplanted from 20 to 1 m depth in La Parguera, Puerto Rico. The UVR exposure by the transplanted colonies was significantly higher than that at 20 m, while photosynthetically active radiation (PAR) only increased by 9%. Photosynthetic pigments, quantified with HPLC, as well as linear extension rates and skeletal densities, were significantly reduced 1 month after transplantation to 1 m depth, while MAAs increased significantly despite immediate paling experienced by transplanted colonies. While these colonies showed a significant reduction in photosynthetic pigments, there were no significant reductions in zooxanthellae densities suggesting photoacclimation of the coral's symbionts to the new radiation conditions. The results suggest that while corals might be able to survive sudden increases in UVR and PAR, their skeletal structure can be greatly debilitated due to a reduction in the photosynthetic capacity of their symbionts and a possible relocation of resources. [source] On the observation of traveling acoustic waves in the solar atmosphere using a magneto-optical filterASTRONOMISCHE NACHRICHTEN, Issue 3-4 2007M. Haberreiter Abstract In contrast to low-frequency waves that are trapped in the cavity of the Sun, high-frequency waves can travel freely in the solar atmosphere. By modelling the observed intensity signal in the red and blue wings of K I 7699 Å and Na I 5890 Å, we aim to better understand the measurements carried out with the Magneto-Optical Filter at Two Heights (MOTH) experiment. We model the observed intensity signal with radiative transfer calculations carried out with the COde for Solar Irradiance (COSI). Furthermore, we derive the formation height of the lines in order to analyze to what extent the contribution functions are modulated by the acoustic waves. We find a phase lag between the red and blue filter for acoustic waves with a frequency above ,7 mHz and conclude that a frequency dependent data analysis is required for higher frequencies. (© 2007 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Energy input and zooplankton species richnessECOGRAPHY, Issue 6 2007Dag O. Hessen What are the relative contribution of temperature and solar irradiance as types of energy deliveries for species richness at the ecosystem level? In order to reveal this question in lake ecosystems, we assessed zooplankton species richness in 1891 Norwegian lakes covering a wide range in latitude, altitude, and lake area. Geographical variables could largely be replaced by temperature-related variables, e.g. annual monthly maximum temperature or growth season. Multivariate analysis (PCA) revealed that not only maximum monthly temperature, but also energy input in terms of solar radiation were closely associated with species richness. This was confirmed by stepwise, linear regression analysis in which lake area was also found to be significant. We tested the predictive power of the "metabolic scaling laws" for species richness by regressing Ln of species richness over the inverse of the air temperature (in Kelvin), corrected for the activation energy (eV) as predicted by the Boltzmann constant. A significant, negative slope of 0.78 for ln richness over temperature, given as 1/kT, was found, thus slightly higher than the range of slopes predicted from the scaling law (0.60,0.70). Temperature basically constrained the upper bound of species number, but it was only a modest predictor of actual richness. Both PCA-analysis and linear regression models left a large unexplained variance probably due to lake-specific properties such as catchment influence, lake productivity, food-web structure, immigration constraints or more stochastic effects. [source] A geochronological approach to understanding the role of solar activity on Holocene glacier length variability in the Swiss AlpsGEOGRAFISKA ANNALER SERIES A: PHYSICAL GEOGRAPHY, Issue 4 2006Anne Hormes ABSTRACT. We present a radiocarbon data set of 71 samples of wood and peat material that melted out or sheared out from underneath eight presentday mid-latitude glaciers in the Central Swiss Alps. Results indicated that in the past several glaciers have been repeatedly less extensive than they were in the 1990s. The periods when glaciers had a smaller volume and shorter length persisted between 320 and 2500 years. This data set provides greater insight into glacier variability than previously possible, especially for the early and middle Holocene. The radiocarbon-dated periods defined with less extensive glaciers coincide with periods of reduced radio-production, pointing to a connection between solar activity and glacier melting processes. Measured long-term series of glacier length variations show significant correlation with the total solar irradiance. Incoming solar irradiance and changing albedo can account for a direct forcing of the glacier mass balances. Long-term investigations of atmospheric processes that are in interaction with changing solar activity are needed in order to understand the feedback mechanisms with glacier mass balances. [source] Photodegradation leads to increased carbon dioxide losses from terrestrial organic matterGLOBAL CHANGE BIOLOGY, Issue 11 2010SUSANNA RUTLEDGE Abstract CO2 production in terrestrial ecosystems is generally assumed to be solely biologically driven while the role of abiotic processes has been largely overlooked. In addition to microbial decomposition, photodegradation , the direct breakdown of organic matter (OM) by solar irradiance , has been found to contribute to litter mass loss in dry ecosystems. Previous small-scale studies have shown that litter degradation by irradiance is accompanied by emissions of CO2. However, the contribution of photodegradation to total CO2 losses at ecosystems scales is unknown. This study determined the proportion of the total CO2 losses caused by photodegradation in two ecosystems: a bare peatland in New Zealand and a seasonally dry grassland in California. The direct effect of solar irradiance on CO2 production was examined by comparing daytime CO2 fluxes measured using eddy covariance (EC) systems with simultaneous measurements made using an opaque chamber and the soil CO2 gradient technique, and with night-time EC measurements under the same soil temperature and moisture conditions. In addition, a transparent chamber was used to directly measure CO2 fluxes from OM caused by solar irradiance. Photodegradation contributed 19% of the annual CO2 flux from the peatland and almost 60% of the dry season CO2 flux from the grassland, and up to 62% and 92% of the summer mid-day CO2 fluxes, respectively. Our results suggest that photodegradation may be important in a wide range of ecosystems with exposed OM. Furthermore, the practice of partitioning daytime ecosystem CO2 exchange into its gross components by assuming that total daytime CO2 losses can be approximated using estimates of biological respiration alone may be in error. To obtain robust estimates of global ecosystem,atmosphere carbon transfers, the contribution of photodegradation to OM decomposition must be quantified for other ecosystems and the results incorporated into coupled carbon,climate models. [source] Alumina Optical Surface Heat Shield for Use in Near-Solar EnvironmentINTERNATIONAL JOURNAL OF APPLIED CERAMIC TECHNOLOGY, Issue 3 2009Don E. King Experiments indicate that coating a heat shield with alumina can significantly reduce spacecraft temperature during operation near the sun. A thin alumina (Al2O3) coating applied to carbon,carbon (C,C) reflects the majority of the visible solar irradiance while reemitting absorbed energy in the infrared. Testing on Al2O3 -coated C,C coupons using visible and NIR lasers (from ambient to 1773 K) show that the solar-absorptance-to-IR emittance ratio (,S/,IR) of the Al2O3 -coated heat shield was 0.6 or less. Compared with an uncoated carbon,carbon heat shield, the coated version is at least 12% cooler, enabling thermal insulation mass reductions, improved scientific measurements, and the use of less exotic thermal protection materials. [source] UV and global solar radiation in ,ód,, Central PolandINTERNATIONAL JOURNAL OF CLIMATOLOGY, Issue 1 2010Agnieszka Podstawczy Abstract With the overall aim of quantifying urban atmospheric effects on different parts of the solar spectrum, a multi year analysis of data collected at ,ód, was undertaken. UV (290,400 nm) and global solar radiation measured by means of a Kipp and Zonen CUV3 radiometer and a Kipp and Zonen CM11 pyranometer in the center of ,ód, between 1997 and 2001 are analysed. The mean annual sum of global and UV solar radiation equaled 3710.8 MJ m,2 and 154.1 MJ m,2, respectively. The minimum monthly total of solar energy occurred in December (48.7 M Jm,2,global; 2.1 MJ m,2,UV); however, the maximum monthly total occurred atypically in May (620.9 MJ m,2,global; 25.3 MJ m,2,UV). UV clearness index (Kuv) is approximately half of the clearness index of the global solar radiation, indicating greater attenuation of that part of the spectrum (Kuv 0.14 in December to 0.26 in May). A linear regression model was fitted to the daily values of UV and global (g) solar irradiation (Duv = a + Dgb). The slope coefficient b and the coefficient of determination equal 0.039 and 0.98, respectively. Cloudiness exerts an important control on the solar radiation flux at the ground level and for the relation between UV and global solar radiation. The convective clouds caused an increase of global and UV solar irradiance by about 10,20% compared to clear days, the enhancement resulting from reflections. On clear days, UV comprises 3.3,4% of global solar irradiance (10-min values) on average, while during cloudy weather it increases to 8%. The results presented have implications for understanding the radiative transfer of UV and global solar radiation in the atmosphere over an urban area and the influence of clouds on transmission of solar radiation flux. Copyright © 2009 Royal Meteorological Society [source] Possible solar control on primary production along the Indian west coast on decadal to centennial timescale,JOURNAL OF QUATERNARY SCIENCE, Issue 2 2009Siby Kurian Abstract Using multiple geochemical proxies including specific biomarkers (dinosterol, phytol, stigmasterol and , -sitosterol) measured in a high-sedimentation rate core collected from the inner shelf (depth ,45,m) off Goa (India), we reconstruct surface productivity, which is mainly controlled by the monsoon upwelling in this region, during the last ca. 700 a. Surface productivity appears to have varied in tandem with the Konkan,Goa rainfall and sunspot activity during the instrumental period (last 250 a). The productivity proxies also covary with the total solar irradiance reconstructed for the period beyond the instrumental era, within the considerable uncertainty of the age model. This suggests that solar forcing may control coastal upwelling intensity and biological productivity in the eastern Arabian Sea on decadal to centennial timescales. During the late Anthropocene (last ca. 50 a), steep increases in all four biomarkers indicate greatly enhanced productivity in response to high solar irradiance as well as anthropogenic inputs of nutrients. Copyright © 2008 John Wiley & Sons, Ltd. [source] Solar disinfection of poliovirus and Acanthamoeba polyphaga cysts in water , a laboratory study using simulated sunlightLETTERS IN APPLIED MICROBIOLOGY, Issue 2 2006W. Heaselgrave Abstract Aims:, To determine the efficacy of solar disinfection (SODIS) in disinfecting water contaminated with poliovirus and Acanthamoeba polyphaga cysts. Methods and Results:, Organisms were subjected to a simulated global solar irradiance of 850 Wm,2 in water temperatures between 25 and 55°C. SODIS at 25°C totally inactivated poliovirus after 6-h exposure (reduction of 4·4 log units). No SODIS-induced reduction in A. polyphaga cyst viability was observed for sample temperatures below 45°C. Total cyst inactivation was only observed after 6-h SODIS exposure at 50°C (3·6 log unit reduction) and after 4 h at 55°C (3·3 log unit reduction). Conclusions:, SODIS is an effective means of disinfecting water contaminated with poliovirus and A. polyphaga cysts, provided water temperatures of 50,55°C are attained in the latter case. Significance and Impact of the Study:, This research presents the first SODIS inactivation curve for poliovirus and provides further evidence that batch SODIS provides effective protection against waterborne protozoan cysts. [source] Changes in convective properties over the solar cycle: effect on p-mode damping ratesMONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY, Issue 2 2001G. Houdek Measurements of both solar irradiance and p-mode oscillation frequencies indicate that the structure of the Sun changes with the solar cycle. Balmforth, Gough & Merryfield investigated the effect of symmetrical thermal disturbances on the solar structure and the resulting pulsation frequency changes. They concluded that thermal perturbations alone cannot account for the variations in both irradiance and p-mode frequencies, and that the presence of a magnetic field affecting acoustical propagation is the most likely explanation of the frequency change, in the manner suggested earlier by Gough & Thompson and by Goldreich et al. Numerical simulations of Boussinesq convection in a magnetic field have shown that at high Rayleigh number the magnetic field can modify the preferred horizontal length scale of the convective flow. Here, we investigate the effect of changing the horizontal length scale of convective eddies on the linewidths of the acoustic resonant mode peaks observed in helioseismic power spectra. The turbulent fluxes in these model computations are obtained from a time-dependent, non-local generalization of the mixing-length formalism. The modelled variations are compared with p-mode linewidth changes revealed by the analysis of helioseismic data collected by the Birmingham Solar-Oscillations Network (BiSON); these low-degree (low- l) observations cover the complete falling phase of solar activity cycle 22. The results are also discussed in the light of observations of solar-cycle variations of the horizontal size of granules and with results from 2D simulations by Steffen of convective granules. [source] Damage to DNA in Bacterioplankton: A Model of Damage by Ultraviolet Radiation and its Repair as Influenced by Vertical Mixing ,PHOTOCHEMISTRY & PHOTOBIOLOGY, Issue 1 2000Yannick Huot ABSTRACT A model of UV-induced DNA damage in oceanic bacterioplankton was developed and tested against previously published and novel measurements of cyclobutane pyrimidine dimers (CPD) in surface layers of the ocean. The model describes the effects of solar irradiance, wind-forced mixing of bacterioplankton and optical properties of the water on net DNA damage in the water column. The biological part includes the induction of CPD by UV radiation and repair of this damage through photoreactivation and excision. The modeled damage is compared with measured variability of CPD in the ocean: diel variation in natural bacterioplankton communities at the surface and in vertical profiles under different wind conditions (net damage as influenced by repair and mixing); in situ incubation of natural assemblages of bacterioplankton (damage and repair, no mixing); and in situ incubation of DNA solutions (no repair, no mixing). The model predictions are generally consistent with the measurements, showing similar patterns with depth, time and wind speed. A sensitivity analysis assesses the effect on net DNA damage of varying ozone thickness, colored dissolved organic matter concentration, chlorophyll concentration, wind speed and mixed layer depth. Ozone thickness and mixed layer depth are the most important factors affecting net DNA damage in the mixed layer. From the model, the total amplification factor (TAF; a relative measure of the increase of damage associated with a decrease in ozone thickness) for net DNA damage in the euphotic zone is 1.7, as compared with 2.1,2.2 for irradiance weighted for damage to DNA at the surface. [source] Engineering photosynthetic light capture: impacts on improved solar energy to biomass conversionPLANT BIOTECHNOLOGY JOURNAL, Issue 6 2007Jan H. Mussgnug Summary The main function of the photosynthetic process is to capture solar energy and to store it in the form of chemical ,fuels'. Increasingly, the photosynthetic machinery is being used for the production of biofuels such as bio-ethanol, biodiesel and bio-H2. Fuel production efficiency is directly dependent on the solar photon capture and conversion efficiency of the system. Green algae (e.g. Chlamydomonas reinhardtii) have evolved genetic strategies to assemble large light-harvesting antenna complexes (LHC) to maximize light capture under low-light conditions, with the downside that under high solar irradiance, most of the absorbed photons are wasted as fluorescence and heat to protect against photodamage. This limits the production process efficiency of mass culture. We applied RNAi technology to down-regulate the entire LHC gene family simultaneously to reduce energy losses by fluorescence and heat. The mutant Stm3LR3 had significantly reduced levels of LHCI and LHCII mRNAs and proteins while chlorophyll and pigment synthesis was functional. The grana were markedly less tightly stacked, consistent with the role of LHCII. Stm3LR3 also exhibited reduced levels of fluorescence, a higher photosynthetic quantum yield and a reduced sensitivity to photoinhibition, resulting in an increased efficiency of cell cultivation under elevated light conditions. Collectively, these properties offer three advantages in terms of algal bioreactor efficiency under natural high-light levels: (i) reduced fluorescence and LHC-dependent heat losses and thus increased photosynthetic efficiencies under high-light conditions; (ii) improved light penetration properties; and (iii) potentially reduced risk of oxidative photodamage of PSII. [source] Investigation to estimate the short circuit current by applying the solar spectrumPROGRESS IN PHOTOVOLTAICS: RESEARCH & APPLICATIONS, Issue 3 2008Jun Tsutsui Abstract The influence of the solar spectrum is investigated to estimate the outdoor short circuit current (Isc) of various photovoltaic (PV) modules. It is well known that the solar spectrum always changes. Hence, it is rare to fit the standard solar spectrum AM1·5G defined in standard IEC 60904-3. In addition, the spectral response (SR) of PV module is different depending on the material. For example, crystal silicon (c-Si) has broad sensitivity that the wavelength range is between 350 and 1150,nm; meanwhile, amorphous silicon (a-Si) has relatively narrow sensitivity comparing to c-Si. Since Isc of the PV module decides by multiplying the solar spectrum and SR together, it is necessary to investigate the solar spectrum to estimate the outdoor Isc in addition to the solar irradiance and module temperature. In this study, the spectral mismatch is calculated and the outdoor Isc is estimated in the whole year. Copyright © 2007 John Wiley & Sons, Ltd. [source] Strong signature of the active Sun in 100 years of terrestrial insolation dataANNALEN DER PHYSIK, Issue 6 2010W. Weber Abstract Terrestrial solar irradiance data of the Smithsonian Astrophysical Observatory from 1905 to 1954 and of Mauna Loa Observatory from 1958 to 2008 are analyzed. The analysis shows that, with changing solar activity, the atmosphere modifies the solar irradiance on the percentage level, in all likelihood via cosmic ray intensity variations produced by the active sun. The analysis strongly suggests that cosmic rays cause a large part of the atmospheric aerosols. These aerosols show specific absorption and scattering properties due to an inner structure of hydrated ionic centers, most probably of O2 - and O2+ produced by the cosmic rays. [source] Comparison between seasons of the ultraviolet environment in the shade of trees in AustraliaPHOTODERMATOLOGY, PHOTOIMMUNOLOGY & PHOTOMEDICINE, Issue 2 2001A. V. Parisi Background/Purpose: This paper has considered the erythemal UV (UVery), UVA and visible irradiances in the shade of Australian trees for each season at a sub-tropical southern hemisphere site. Methods: The irradiances in tree shade have been measured with radiometers as a percentage of the irradiances in the sun for each season of the year. Results: Although the solar irradiances are lower in winter, the percentages of the UV in tree shade compared to the UV in full sun are marginally higher (by up to 7%) in the winter compared to summer. The range of percentages for UVery was up to double that of the percentages of the visible waveband. The percentages for UVery were also higher than for the UVA waveband. The percentages of the irradiances in the tree shade compared to full sun are 8,14% lower at noon compared to the morning and afternoon for the UVery waveband. The ratio of UVA to UVery is lower in the tree shade compared to the full sun. Conclusions: The UVA to UVery ratio is expected to be even lower in the tree shade as a result of ozone depletion. This, combined with the visible irradiances in the tree shade not being a reliable indication of the biologically damaging UV irradiances, has consequences for public health and skin cancer prevention. [source] | ||||||||||||||||