scholarly journals Experimental Evaluation of a Spectral Index to Characterize Temporal Variations in the Direct Normal Irradiance Spectrum

2021 ◽  
Vol 11 (3) ◽  
pp. 897
Author(s):  
Gustavo Nofuentes ◽  
Christian A. Gueymard ◽  
José A. Caballero ◽  
Guilherme Marques-Neves ◽  
Jorge Aguilera
Keyword(s):  
Solar Spectrum ◽  
Temporal Variations ◽  
Simple Index ◽  
Direct Normal Irradiance ◽  
Spectrum Distribution ◽  
Spectral Distributions ◽  
Single Number ◽  
The Relationship ◽  
Average Photon Energy ◽  
Irradiance Spectrum

A simple index is desirable to assess the effects on both flat-plate and concentrating photovoltaics of natural changes in the solar spectrum. Some studies have suggested that the relationship between the Average Photon Energy (APE) and the shape of individual global tilted irradiance, global horizontal irradiance, or direct normal irradiance (DNI) spectra is bijective and can therefore be used as a single number to unequivocally replace a complete spectral distribution. This paper reevaluates these studies with a modified methodology to assess whether a one-to-one relationship really exists between APE and spectral DNI. A 12-month dataset collected in Jaén (Spain) using a sun-tracking spectroradiometer provides the necessary spectral DNI data between 350 and 1050 nm. After quality control and filtering, 78,772 valid spectra were analyzed. The methodology is based on a statistical analysis of the spectral distributions binned in 0.02-eV APE intervals, from 1.74 to 1.90 eV. For each interval, both the standard deviation and coefficient of variation (CV) are determined across all 50-nm bands into which the 350–1050-nm waveband is divided. CV stays below 3.5% within the 450–900-nm interval but rises up to 13% outside of it. It is concluded that APE may be approximately assumed to uniquely characterize the DNI spectrum distribution for Jaén (and presumably for locations with similar climates) only over the limited 450–900-nm waveband.

scholarly journals Monitoring spatial and temporal variations of surface albedo on Saint Sorlin Glacier (French Alps) using terrestrial photography

2011 ◽  
Vol 5 (1) ◽  
pp. 271-305
Author(s):  
M. Dumont ◽  
P. Sirguey ◽  
Y. Arnaud ◽  
D. Six
Keyword(s):  
Mass Balance ◽  
Near Infrared ◽  
Solar Spectrum ◽  
Incident Radiation ◽  
Temporal Variations ◽  
Radiative Transfer Model ◽  
Transfer Model ◽  
Glacier Mass Balance ◽  
Infrared Wavelengths ◽  
The Relationship

Abstract. Accurate knowledge of temperate glacier mass balance is essential to understand the relationship between glacier and climate. Defined as the reflected fraction of incident radiation over the whole solar spectrum, the surface broadband albedo is one of the leading variable of their mass balance. This study presents a new method to retrieve the albedo of frozen surfaces from terrestrial photography at visible and near infrared wavelengths. This method accounts for the anisotropic reflectance of snow and ice surfaces and uses a radiative transfer model for narrow-to-broadband conversion. The accuracy of the method was assessed using concomitant measurements of albedo during the summers 2008 and 2009 on Saint Sorlin Glacier (Grandes Rousses, France). These albedo measurements are performed at two locations on the glacier, one in the ablation area and the other in the accumulation zone, with a net radiometer Kipp and Zonen CNR1. Main sources of uncertainty are associated with the presence of high clouds and the georeferencing of the photographs.

scholarly journals CO2 dynamics and heterogeneity in a cave atmosphere: role of ventilation patterns and airflow pathways

2021 ◽  
Author(s):  
Lovel Kukuljan ◽  
Franci Gabrovšek ◽  
Matthew D. Covington ◽  
Vanessa E. Johnston
Keyword(s):  
Temporal Variations ◽  
Observation Point ◽  
Spatially Distributed ◽  
Combined Action ◽  
Karst Systems ◽  
The Relationship ◽  
Co2 Dynamics ◽  
Global Carbon

AbstractUnderstanding the dynamics and distribution of CO2 in the subsurface atmosphere of carbonate karst massifs provides important insights into dissolution and precipitation processes, the role of karst systems in the global carbon cycle, and the use of speleothems for paleoclimate reconstructions. We discuss long-term microclimatic observations in a passage of Postojna Cave, Slovenia, focusing on high spatial and temporal variations of pCO2. We show (1) that the airflow through the massif is determined by the combined action of the chimney effect and external winds and (2) that the relationship between the direction of the airflow, the geometry of the airflow pathways, and the position of the observation point explains the observed variations of pCO2. Namely, in the terminal chamber of the passage, the pCO2 is low and uniform during updraft, when outside air flows to the site through a system of large open galleries. When the airflow reverses direction to downdraft, the chamber is fed by inlets with diverse flow rates and pCO2, which enter via small conduits and fractures embedded in a CO2-rich vadose zone. If the spatial distribution of inlets and outlets produces minimal mixing between low and high pCO2 inflows, high and persistent gradients in pCO2 are formed. Such is the case in the chamber, where vertical gradients of up to 1000 ppm/m are observed during downdraft. The results presented in this work provide new insights into the dynamics and composition of the subsurface atmosphere and demonstrate the importance of long-term and spatially distributed observations.

scholarly journals On the Relationship between Teleconnections and Taiwan's Streamflow: Evidence of Climate Regime Shift and Implications for Seasonal Forecasting

2016 ◽  
Author(s):  
Chia-Jeng Chen ◽  
Tsung-Yu Lee
Keyword(s):  
Large Scale ◽  
Critical Role ◽  
Phase Relationship ◽  
Temporal Variations ◽  
Pacific Basin ◽  
Climate Regime ◽  
Quasi Biennial Oscillation ◽  
Teleconnection Patterns ◽  
Integrated Response ◽  
The Relationship

Abstract. Interannual variations of catchment streamflow represent an integrated response to anomalies in regional moisture transport and atmospheric circulations, ultimately linked to large-scale climate oscillations. This study investigates the relationship between Taiwan's long-term summertime (July to September, JAS) streamflow and manifold teleconnection patterns. Lagged correlation analysis is conducted to calculate how JAS streamflow data derived at 28 upstream and 13 downstream gauges in Taiwan correlate with 14 teleconnection indices in the concurrent or preceding seasons. Out of the many indices, the West-Pacific and Pacific-Japan (PJ) patterns, both of which play a critical role in determining cyclonic activity in the western North Pacific basin, exhibit the highest concurrent correlations (most significant r = 0.48) with the JAS flows in Taiwan. At a one-month lead time, on the other hand, the Quasi-Biennial Oscillation significantly correlate with the JAS flows (most significant r = −0.66), indicating some forecasting utility. By further examining the correlation results using a 20-year moving window, peculiar temporal variations and possible climate regime shifts (CRS) can be revealed. To identify suspicious, abrupt changes in the correlation, a CRS test is employed. The late 1970s and 1990s are identified as two significant change points, and during the intermediate period, a marked in-phase relationship (r ~ 0.9) between Taiwan's streamflow and the PJ index is observed. It is verified that the two shifts are in concordance with the alteration of large-scale circulations in the Pacific basin. Discussion about the changes in pattern correlation and composite maps before and after the change point is carried out, and our results suggest that empirical forecasting techniques should take into account the effect of CRS on predictor screening.

scholarly journals Analysing Tuberculosis Trends in South Asia

2018 ◽  
Vol 8 (6) ◽  
pp. 5245
Author(s):  
Kumar Abhishek ◽  
M. P Singh ◽  
Md. Sadik Hussain
Keyword(s):  
Sri Lanka ◽  
World Health Organization ◽  
South Asia ◽  
Causes Of Death ◽  
Temporal Variations ◽  
World Health ◽  
Spatial And Temporal Variations ◽  
The World ◽  
Health Organization ◽  
The Relationship

<p>Tuberculosis (TB) has been one of the top ten causes of death in the world. As per the World Health Organization (WHO) around 1.8 million people have died due to tuberculosis in 2015. This paper aims to investigate the spatial and temporal variations in TB incident in South Asia (India, Bangladesh, Pakistan, Maldives, Nepal, and Sri-Lanka). Asia had been counted for the largest number of new TB cases in 2015. The paper underlines and relates the relationship between various features like gender, age, location, occurrence, and mortality due to TB in these countries for the period 1993-2012.</p>

scholarly journals Temperature regime studies and mathematical calculations for dry snow covers in the western Tien Shan mountains, China

1992 ◽  
Vol 16 ◽  
pp. 185-189
Author(s):  
Ma Hong ◽  
Liu Zongchao ◽  
Yang Zhian
Keyword(s):  
Internal Heat ◽  
Internal Heat Source ◽  
Temporal Variations ◽  
Tien Shan ◽  
Atmospheric Conditions ◽  
One Dimensional ◽  
Mass Transfer Processes ◽  
The Relationship ◽  
Tien Shan Mountains ◽  
Snow Temperature

A mathematical model is proposed to simulate the spatial and temporal variations in snow temperature. The model is based on the non-steady, one-dimensional, heat-conduction equation with internal heat source. It gives the change in time of the internal temperature field of the snow as it responds to varying surface temperature and periodic solar radiation. Verification of the model is accomplished by comparing the calculated results with observed data. The model may serve as a basis for quantitative investigations of snow temperature and temperature gradient, and relevent problems such as energy-mass transfer processes. Moreover, it allows better understanding of the relationship between external atmospheric conditions and the internal thermal regime of dry snow covers in the western Tien Shan mountains.

scholarly journals Spatially cascading effect of perturbations in experimental meta-ecosystems

2016 ◽  
Vol 283 (1838) ◽  
pp. 20161496 ◽  
Author(s):  
Eric Harvey ◽  
Isabelle Gounand ◽  
Pravin Ganesanandamoorthy ◽  
Florian Altermatt
Keyword(s):  
Population Dynamics ◽  
Community Dynamics ◽  
Local Community ◽  
Local Population ◽  
Temporal Variations ◽  
Landscape Scale ◽  
Cascading Effect ◽  
Regional Dynamics ◽  
The Relationship ◽  
Over Time

Ecosystems are linked to neighbouring ecosystems not only by dispersal, but also by the movement of subsidy. Such subsidy couplings between ecosystems have important landscape-scale implications because perturbations in one ecosystem may affect community structure and functioning in neighbouring ecosystems via increased/decreased subsidies. Here, we combine a general theoretical approach based on harvesting theory and a two-patch protist meta-ecosystem experiment to test the effect of regional perturbations on local community dynamics. We first characterized the relationship between the perturbation regime and local population demography on detritus production using a mathematical model. We then experimentally simulated a perturbation gradient affecting connected ecosystems simultaneously, thus altering cross-ecosystem subsidy exchanges. We demonstrate that the perturbation regime can interact with local population dynamics to trigger unexpected temporal variations in subsidy pulses from one ecosystem to another. High perturbation intensity initially led to the highest level of subsidy flows; however, the level of perturbation interacted with population dynamics to generate a crash in subsidy exchange over time. Both theoretical and experimental results show that a perturbation regime interacting with local community dynamics can induce a collapse in population levels for recipient ecosystems. These results call for integrative management of human-altered landscapes that takes into account regional dynamics of both species and resource flows.

The Noise Characteristics Research in Subway Cars

2014 ◽  
Vol 1051 ◽  
pp. 431-434
Author(s):  
Jian Hui Tian ◽  
Lian Jian ◽  
Bing Li
Keyword(s):  
Real Time ◽  
High Frequency ◽  
Noise Spectrum ◽  
Frequency Range ◽  
Noise Characteristics ◽  
Spectrum Distribution ◽  
Spectrum Characteristics ◽  
Relationship Of ◽  
The Relationship

The noise of different points in four sections of Shenzhen subway was tested by this paper. Real-time SPL and noise spectrum distribution curves at bogie were given, while the equivalent SPL curve was also shown. The relationship of subway speed and noise SPL was investigated. The regular of noise spectrum characteristics and SPL was obtained. The results show that the noise SPL increases with the increase of the speed. Looking from the frequency range, the frequency corresponding to larger noise SPL amplitude mainly concentrates in the lower frequency while the subway stopping, the frequency corresponding to larger noise SPL amplitude mainly concentrates in high frequency while the subway running.

Impact of average photon-energy coefficient of solar spectrum on the short circuit current of photovoltaic modules

2017 ◽  
Vol 17 (10) ◽  
pp. 1341-1346 ◽  
Author(s):  
Yuhei Horio ◽  
Md. Mijanur Rahman ◽  
Yurei Imai ◽  
Yoshihiro Hishikawa ◽  
Takashi Minemoto
Keyword(s):  
Photon Energy ◽  
Short Circuit ◽  
Solar Spectrum ◽  
Short Circuit Current ◽  
Photovoltaic Modules ◽  
Energy Coefficient ◽  
Average Photon Energy

scholarly journals DISTRIBUCIÓN Y DENSIDAD DE ICTIOPLANCTON EN EL ESTUARIO DE BAHÍA MÁLAGA, PACÍFICO COLOMBIANO (SEPTIEMBRE DE 2009-FEBRERO DE 2010)

2016 ◽  
Vol 43 (1) ◽  
Author(s):  
Diana Medina Contreras ◽  
Jaime Cantera ◽  
Eugenia Escarria ◽  
Luz M Mejía Ladino
Keyword(s):  
Fish Assemblages ◽  
Larval Fish ◽  
Fish Larvae ◽  
Larval Density ◽  
Temporal Distribution ◽  
Mesh Size ◽  
Temporal Variations ◽  
Taxonomic Composition ◽  
Total Density ◽  
The Relationship

The density, taxonomic composition, and spatial and temporal distribution of the estuarine ichthyoplankton of Bahía Málaga (Pacific coast of Colombia) are described, as well as the relationship between biological parameters and some physicochemical variables. Samples were collected at 12 stations along the principal navigation canal; these samples were taken in four areas following the design of Barletta-Bergan. Surface sweeps were carried out with a conical-cylindrical net (mesh size 500 µm, mouth diameter 0.6 m, length 3.5 m). Salinity and temperature were measured before each sweep. A total of 69019 larvae/1000 m³, representing 23 families, 36 genera and 40 species were collected during monthly sampling from September, 2009 to February, 2010. Carangidae (39.0%) was the most abundant family, followed by Sciaenidae (27.1%) and Engraulidae (20.1%). The most frequent families were Sciaenidae (26.6%), followed by Carangidae (22.8%) and Engraulidae (14.7%) which are important families in larval fish assemblages in tropical estuaries. Eighty percent of total density was provided by six species, of which Seriola morphotype 1 (Carangidae) and Cetengraulis mysticetus (Engraulidae) were the most abundant and dominant. No correlation was found between density and salinity (Spearman, R = 0.23) or temperature (Spearman, R = 0.51). Analysis of spatial and temporal variations of larval density shows significant differences among the months sampled (Anova, p = 0.0029; p < 0.05), but not among areas (Anova, p = 0.078), suggesting that Bahía Málaga offers adequate conditions for the presence of fish larvae.

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