scholarly journals Long-term observations of supraglacial streams on an Arctic glacier

2019 ◽  
Vol 65 (254) ◽  
pp. 900-911 ◽  
Author(s):  
Sarah L. St Germain ◽  
Brian J. Moorman
Keyword(s):  
Solar Radiation ◽  
Unmanned Aerial Vehicles ◽  
Aerial Imagery ◽  
Digital Elevation ◽  
Small Streams ◽  
Hydrological System ◽  
Arctic Glacier ◽  
The Impact ◽  
Stream Formation

AbstractSupraglacial streams are a significant part of the glacial hydrological system and important for understanding glacial hydrology and dynamics. Here we infer factors that influence the long-term development of perennial supraglacial streams, particularly in reference to canyon, incised and surface stream formation. Orthophotos and digital elevation models generated from high-resolution aerial imagery taken with unmanned aerial vehicles or piloted helicopters between 2010 and 2017 were used to compare seven streams on Fountain Glacier, Bylot Island, Canada over time. Results show canyon formation occurs from a combination of fluvial processes and the impact of solar radiation. The greater the discharge or slope, the faster the incision and higher the sinuosity. With greater sinuosity, the distance between the top of the valley banks increases, and cutoffs cause trapezoidal canyon-like valleys to form. Solar radiation causes the backward migration of the valley walls, further enhancing canyon area. Canyons are less likely to occur in areas of low discharge and slope. Less incised channels are also more likely to have water flow jumping the channel banks, changing the channel path. The presence of medial moraines and crevasses also increases rerouting of small streams. Lastly, windblown created snow-plugs may lead to stream diversion.

scholarly journals Improving the reliability of cable lines operation in hot climates

2020 ◽  
Vol 216 ◽  
pp. 01151
Author(s):  
Daniyar Bakhtiyarovich Madrakhimov ◽  
Vera Pavlovna Ivanova ◽  
Victoria Vyacheslavovna Tsypkina
Keyword(s):  
Solar Radiation ◽  
Climatic Factors ◽  
Climate Conditions ◽  
Term Operation ◽  
Asian Region ◽  
Hot Climate ◽  
Central Asian ◽  
Cable Lines ◽  
The Impact

Reliability of cable lines in hot climate is determined by the climatic characteristics of cables and wires, which include: long-term and short-term heat resistance, cold resistance, moisture resistance, resistance to cyclic exposure to temperatures and solar radiation, ozone resistance, etc. This article considers the main impacts of environmental factors: high temperatures, solar radiation, which, as practice shows, lead to irreversible deterioration of the electrical and mechanical properties of cable products. The result of climatic impacts in the Central Asian region, in hot climate conditions, is the aging of both insulation and protective coverings, which leads to irreversible change in the mechanical and electrical properties of the used polymers due to the loss of elasticity of the extruded material and its subsequent cracking, turning into cracks. The assessment of the possibility of long-term operation of the used polymer was carried out according to the polyethylene oxidation period, which determines the time of natural preservation of various types of cables during the period of their operation. The research was carried out on samples of cables stored under a canopy in wooden boxes, protected from sunlight and precipitation, by measuring criterion parameters with strict compliance with the established norms. Thus, the proposed solution for increasing the reliability of cable lines consists of debugging the technological process of applying insulation and sheathing, in which the extrusion of the polymer mass is carried out by technique that minimizes the ingress of contamination. Review of the results showed that extrusion line improvement would provide possibility of increasing reliability in the operation of cable products under the impact of climatic factors of the Central Asian region due to the reduced aging of insulation.

scholarly journals Merging ground-based sunshine duration observations with satellite cloud and aerosol retrievals to produce high-resolution long-term surface solar radiation over China

2021 ◽  
Vol 13 (3) ◽  
pp. 907-922
Author(s):  
Fei Feng ◽  
Kaicun Wang
Keyword(s):  
Standard Deviation ◽  
High Resolution ◽  
Solar Radiation ◽  
Spatial Resolution ◽  
Sunshine Duration ◽  
Ordinary Least Squares ◽  
Cloud Fraction ◽  
Surface Solar Radiation ◽  
The Impact

Abstract. Although great progress has been made in estimating surface solar radiation (Rs) from meteorological observations, satellite retrieval, and reanalysis, getting best-estimated long-term variations in Rs are sorely needed for climate studies. It has been shown that Rs data derived from sunshine duration (SunDu) can provide reliable long-term variability, but such data are available at sparsely distributed weather stations. Here, we merge SunDu-derived Rs with satellite-derived cloud fraction and aerosol optical depth (AOD) to generate high-spatial-resolution (0.1∘) Rs over China from 2000 to 2017. The geographically weighted regression (GWR) and ordinary least-squares regression (OLS) merging methods are compared, and GWR is found to perform better. Based on the SunDu-derived Rs from 97 meteorological observation stations, which are co-located with those that direct Rs measurement sites, the GWR incorporated with satellite cloud fraction and AOD data produces monthly Rs with R2=0.97 and standard deviation =11.14 W m−2, while GWR driven by only cloud fraction produces similar results with R2=0.97 and standard deviation =11.41 W m−2. This similarity is because SunDu-derived Rs has included the impact of aerosols. This finding can help to build long-term Rs variations based on cloud data, such as Advanced Very High Resolution Radiometer (AVHRR) cloud retrievals, especially before 2000, when satellite AOD retrievals are not unavailable. The merged Rs product at a spatial resolution of 0.1∘ in this study can be downloaded at https://doi.org/10.1594/PANGAEA.921847 (Feng and Wang, 2020).

Terrestrial Solar Radiation

2017 ◽  
pp. 191-293
Keyword(s):  
Solar Radiation ◽  
Horizontal Plane ◽  
Cloud Cover ◽  
Weather Conditions ◽  
Clear Sky ◽  
Solar Tracking ◽  
Sky Conditions ◽  
The Impact ◽  
Estimation Models

After shading a light on the extraterrestrial solar radiation in the chapter 3 it is important to evaluate the global terrestrial solar radiation and its components. The information on terrestrial solar radiation is required in several different forms depending on the kinds of calculations and kind of application that are to be done. Of course, terrestrial solar radiation on the horizontal plane depends on the different weather conditions such as cloud cover, relative humidity, and ambient temperature. Therefore, the impact of the atmosphere on solar radiation should be considered. One of the most important points of terrestrial solar radiation evaluation is its determination during clear sky conditions. Therefore, in this chapter, the equations that determine the air mass basing on available theories are given and the clear sky conditions are introduced with shading a light on the previous work in identifying clear sky conditions. Taking into consideration that, clear sky solar radiation estimation is of great importance for solar tracking, a detailed review of main available models is given in this chapter. As daily, monthly, seasonally, biannually and yearly mean daily solar radiations are required information for designing and installing long term tracking systems, different available methods are commented regarding their applicability for the estimation of solar radiation information in the desired format from the data that are available. An important accent is paid also on the assessment and comparison of monthly mean daily solar radiation estimation models.

Estimation of solar radiation from digital elevation model in area of rough topography

2016 ◽  
Vol 13 (5) ◽  
pp. 453-460 ◽  
Author(s):  
Lurwan Mahmoud Sabo ◽  
Norman Mariun ◽  
Hashim Hizam ◽  
Mohd Amran Mohd Radzi ◽  
Azmi Zakaria
Keyword(s):  
Solar Radiation ◽  
Digital Elevation Model ◽  
Spatial Data ◽  
Energy Planning ◽  
Solar Photovoltaic ◽  
Content Type ◽  
Digital Elevation ◽  
Elevation Model ◽  
The Impact ◽  
Topographic Parameters

Purpose The purpose of this study is to evaluate the reliability of the technique for estimating solar radiation in areas of rough topography and to detect the source of error and means for improvement. Design/methodology/approach Spatial data of the study area in the form of digital elevation model (DEM) coupled with geographic information system (GIS) were used to estimate the monthly solar radiation at locations with rough topography. The generated data were compared with measured data collected from all the selected locations using NASA data. Findings The results show that the variation in topographic parameters has a strong influence on the amount of solar radiation received by two close locations. However, the method performed well for solar radiation estimated in the areas of rough topography. Research limitations/implications The proposed approach overestimates the monthly solar radiation as compared with NASA data due to the impact of topographic parameters accounted for by the model which are not accounted by conventional methods of measurements. This approach can be improved by incorporating the reflected component of radiation in the model used to estimate the solar radiation implemented in the GIS. Originality/value The approach of using GIS with DEM to estimate solar radiation enables to identify the spatial variability in solar radiation between two closest locations due to the influence of topographic parameters, and this will assist in proper energy planning and decision making for optimal areas of solar photovoltaic installation.

scholarly journals Merging ground-based sunshine duration with satellite cloud and aerosol data to produce high resolution long-term surface solar radiation over China

2020 ◽  
Author(s):  
Fei Feng ◽  
Kaicun Wang
Keyword(s):  
Standard Deviation ◽  
High Resolution ◽  
Solar Radiation ◽  
Spatial Resolution ◽  
Sunshine Duration ◽  
Ordinary Least Squares ◽  
Cloud Fraction ◽  
Surface Solar Radiation ◽  
The Impact

Abstract. Although great progress has been made in estimating surface solar radiation (Rs) from meteorological observations, satellite retrieval and reanalysis, getting best estimated of long-term variations in Rs are sorely needed for climate studies. It has been shown that sunshine duration (SunDu)-derived Rs data can provide reliable long-term Rs variation. Here, we merge SunDu-derived Rs data with satellite-derived cloud fraction and aerosol optical depth (AOD) data to generate high spatial resolution (0.1°) Rs over China from 2000 to 2017. The geographically weighted regression (GWR) and ordinary least squares regression (OLS) merging methods are compared, and GWR is found to perform better. Whether or not AOD is taken as input data makes little difference for the GWR merging results. Based on the SunDu-derived Rs from 97 meteorological observation stations, the GWR incorporated with satellite cloud fraction and AOD data produces monthly Rs with R2 = 0.97 and standard deviation = 11.14 W/m2, while GWR driven by only cloud fraction produces similar results with R2 = 0.97 and standard deviation = 11.41 w/m2. This similarity is because SunDu-derived Rs has included the impact of aerosols. This finding can help to build long-term Rs variations based on cloud data, such as Advanced Very High Resolution Radiometer (AVHRR) cloud retrievals, especially before 2000, when satellite AOD retrievals are not unavailable. The merged Rs product at a spatial resolution of 0.1° in this study can be downloaded at https://doi.pangaea.de/10.1594/PANGAEA.921847 (Feng and Wang, 2020).

scholarly journals Effects of digital elevation model spatial resolution on distributed calculations of solar radiation loading on a High Arctic glacier

2009 ◽  
Vol 55 (194) ◽  
pp. 973-984 ◽  
Author(s):  
Neil Arnold ◽  
Gareth Rees
Keyword(s):  
High Resolution ◽  
Solar Radiation ◽  
High Arctic ◽  
Airborne Lidar ◽  
Distributed Model ◽  
Height Measurement ◽  
Glacier Surface ◽  
Direct Beam ◽  
Digital Elevation ◽  
The Impact

AbstractHigh-resolution airborne lidar data are used to produce digital elevation models (DEMs) of an arctic valley glacier (midre Lovénbreen, Svalbard) at resolutions of 2.5–2000 m, using three different interpolation schemes. These data are used in a distributed model of solar radiation loading for glaciers. When the mean of all lidar measurements within a DEM cell is used to calculate cell height, the differences between the finest- (2.5 m) and coarsest-resolution (2000 m) DEMs for the calculated annual whole-glacier spatial means of total potential direct-beam solar radiation, potential duration of direct-beam solar radiation, and intensity of potential direct-beam solar radiation are 20%, 56% and −23% of the 2.5 m DEM values respectively. A resolution change from 2.5 m to 200 m affects the whole-glacier spatial mean summer net solar radiative flux by an average of 5%, and the summer melt production from the glacier by an average of 3% compared with the 2.5 m DEM values, for the years 2001–03. These changes are largely driven by underestimation of shading by surrounding topography at coarser DEM resolutions. This dependency is reduced in the second and third interpolation schemes, especially at resolutions finer than 50 m, which use the maximum lidar height measurement in some or all DEM cells. These results suggest that resolutions of ∼50 m are the coarsest that should be adopted in high-resolution glacier surface energy-balance models for glaciers of similar size and in similar topographic situations to midre Lovénbreen, and that the impact of DEM resolution on calculated solar radiation receipts can be reduced by an appropriate choice of DEM interpolation scheme.

Environmental trends in the variation of biologically active phenolic compounds in Labrador tea, Rhododendron groenlandicum, from northern Quebec, Canada

Botany ◽  
2014 ◽  
Vol 92 (11) ◽  
pp. 783-794 ◽  
Author(s):  
Michel Rapinski ◽  
Rui Liu ◽  
Ammar Saleem ◽  
John Thor Arnason ◽  
Alain Cuerrier
Keyword(s):  
Phenolic Compounds ◽  
Solar Radiation ◽  
Latitudinal Gradient ◽  
Biologically Active ◽  
Short Term ◽  
Marker Compounds ◽  
Labrador Tea ◽  
Quercetin Glycoside ◽  
The Impact

The impact of several environmental factors on the production of phenolic compounds in a North American medicinal plant, Labrador tea (Rhododendron groenlandicum (Oeder) Kron & Judd), was studied. Leaves were harvested in 2006 and 2010 over a latitudinal gradient in northern Quebec, and known phenolic markers were quantified by HPLC-DAD. The concentration of selected compounds varied geographically where they were higher between the 51st and 53rd parallel of northern Quebec and lower in the peripheral northern and southern region. Major variations were observed in the following marker compounds: (+)-catechin, (–)-epicatechin, quercetin-3-galactoside, and an undetermined quercetin-glycoside. The variation in phenolic compounds was best explained by short-term changes in annual temperature range and long-term estimates of insolation parameters such as solar radiation and photoperiod in the month of June.

Suppressed, but Not Forgotten

2011 ◽  
Vol 70 (1) ◽  
pp. 5-11 ◽  
Author(s):  
Beat Meier ◽  
Anja König ◽  
Samuel Parak ◽  
Katharina Henke
Keyword(s):  
Memory Trace ◽  
Thought Suppression ◽  
Test Phase ◽  
Indirect Test ◽  
Final Test ◽  
Test Experiment ◽  
And Control ◽  
Cue Words ◽  
The Impact

This study investigates the impact of thought suppression over a 1-week interval. In two experiments with 80 university students each, we used the think/no-think paradigm in which participants initially learn a list of word pairs (cue-target associations). Then they were presented with some of the cue words again and should either respond with the target word or avoid thinking about it. In the final test phase, their memory for the initially learned cue-target pairs was tested. In Experiment 1, type of memory test was manipulated (i.e., direct vs. indirect). In Experiment 2, type of no-think instructions was manipulated (i.e., suppress vs. substitute). Overall, our results showed poorer memory for no-think and control items compared to think items across all experiments and conditions. Critically, however, more no-think than control items were remembered after the 1-week interval in the direct, but not in the indirect test (Experiment 1) and with thought suppression, but not thought substitution instructions (Experiment 2). We suggest that during thought suppression a brief reactivation of the learned association may lead to reconsolidation of the memory trace and hence to better retrieval of suppressed than control items in the long term.

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