scholarly journals Quasi-biennial and longer-term changes in clear sky UV-B solar irradiance

1998 ◽  
Vol 25 (23) ◽  
pp. 4345-4348 ◽  
Author(s):  
C. Zerefos ◽  
C. Meleti ◽  
D. Balis ◽  
K. Tourpali ◽  
A. F. Bais
Keyword(s):  
Solar Irradiance ◽  
Clear Sky

scholarly journals Albedo and estimates of net radiation for green beans under polyethylene cover and field conditions

1999 ◽  
Vol 34 (10) ◽  
pp. 1763-1774 ◽  
Author(s):  
José Leonaldo de Souza ◽  
João Francisco Escobedo ◽  
Maria Terezinha Trovareli Tornero
Keyword(s):  
Solar Irradiance ◽  
Field Conditions ◽  
Net Radiation ◽  
Phaseolus Vulgaris L ◽  
Green Beans ◽  
Phenological Stages ◽  
Independent Variables ◽  
Clear Sky ◽  
Solar Elevation ◽  
Global Irradiance

This paper describes the albedo (r) and estimates of net radiation and global solar irradiance for green beans crop (Phaseolus vulgaris L.), cultivated in greenhouse with cover of polyethylene and field conditions, in Botucatu, SP, Brazil (22º 54' S; 48º 27' W; 850 m). The solar global irradiance (Rg) and solar reflected radiation (Rr) were used to estimate the albedo through the ratio between Rr and Rg. The diurnal curves of albedo were obtained for days with clear sky and partially cloudy conditions, for different phenological stages of the crop. The albedo ranged with the solar elevation, the environment and the phenological stages. The cloudiness range have almost no influence on the albedo diurnal amount. The estimation of radiation were made by linear regression, using the global solar irradiance (Rg) and net short-waves radiation (Rc) as independent variables. All estimates of radiation showed better adjustment for specific phenological periods compared to the entire crop growing cycle. The net radiation in the greenhouse has been estimated by the global solar irradiance measured at field conditions.

Improvement of clear sky models for direct solar irradiance considering turbidity factor variable during the day

2020 ◽  
Vol 161 ◽  
pp. 559-569 ◽  
Author(s):  
Camelia Liliana Moldovan ◽  
Radu Păltănea ◽  
Ion Visa
Keyword(s):  
Solar Irradiance ◽  
Clear Sky ◽  
Factor Variable

scholarly journals Technical note: A low-cost albedometer for snow and ice measurements – Theoretical results and application on a tropical mountain in Bolivia

2018 ◽  
Author(s):  
Thomas Condom ◽  
Marie Dumont ◽  
Lise Mourre ◽  
Jean Emmanuel Sicart ◽  
Antoine Rabatel ◽  
...  
Keyword(s):  
Solar Irradiance ◽  
Low Cost ◽  
Spectral Response ◽  
Lateral Moraine ◽  
Clear Sky ◽  
Direct Observations ◽  
Right Hand ◽  
The Right ◽  
Theoretical Results ◽  
Daily Time

Abstract. This study presents a new instrument called a low-cost albedometer (LCA) composed of two illuminance sensors that are used to measure in-situ incident and reflected illuminance values on a daily timescale. The ratio between reflected vs. incident illuminances is called the albedo index and can be compared with actual albedo values. Due to the shape of the sensor, the direct radiation for zenith angles ranging from 55° to 90° is not measured. The spectral response of the LCA varies with the solar irradiance wavelengths within the range 0.26 to 1.195 µm, and the LCA detects 85 % of the total spectral solar irradiance for clear sky conditions. We first consider the theoretical results obtained for 10 different ice and snow surfaces with clear sky and cloudy sky incident solar irradiance that show that the LCA spectral response may be responsible for an overestimation of the theoretical albedo values by roughly 9 % at most. Then, the LCA values are compared with two classical albedometers over a one-year measurement period (2013) for two sites in a tropical mountainous catchment in Bolivia. One site is located on the Zongo Glacier (i.e. snow and ice surfaces) and the second one is found on the right-hand side lateral moraine (bare soil and snow surfaces). The results, at daily time steps (256 days), given by the LCA are in good agreement with the classic albedo measurements taken with pyranometers with R2 = 0.83 (RMSD = 0.10) and R2 = 0.92 (RMSD = 0.08) for the Zongo Glacier and the right-hand side lateral moraine, respectively. This demonstrates that our system performs well and thus provides relevant opportunities to document spatio-temporal changes in the surface albedo from direct observations at the scale of an entire catchment at a low cost. Finally, during the period from September 2015 to June 2016, direct observations were collected with 15 LCAs on the Zongo Glacier and successfully compared with LANDSAT images showing the surface state of the glacier (i.e. snow or ice). This comparison illustrates the efficiency of this system to monitor the daily time step changes in the snow/ice coverage distributed on the glacier.

scholarly journals Satellite-Based Estimation of Temporally Resolved Dust Radiative Forcing in Snow Cover

2016 ◽  
Vol 17 (7) ◽  
pp. 1999-2011 ◽  
Author(s):  
Steven D. Miller ◽  
Fang Wang ◽  
Ann B. Burgess ◽  
S. McKenzie Skiles ◽  
Matthew Rogers ◽  
...  
Keyword(s):  
Solar Irradiance ◽  
Radiative Forcing ◽  
Hydrological Cycle ◽  
Clear Sky ◽  
Operational Management ◽  
Moderate Resolution ◽  
Resolution Imaging ◽  
Moderate Resolution Imaging Spectroradiometer ◽  
Sky Conditions

Abstract Runoff from mountain snowpack is an important freshwater supply for many parts of the world. The deposition of aeolian dust on snow decreases snow albedo and increases the absorption of solar irradiance. This absorption accelerates melting, impacting the regional hydrological cycle in terms of timing and magnitude of runoff. The Moderate Resolution Imaging Spectroradiometer (MODIS) Dust Radiative Forcing in Snow (MODDRFS) satellite product allows estimation of the instantaneous (at time of satellite overpass) surface radiative forcing caused by dust. While such snapshots are useful, energy balance modeling requires temporally resolved radiative forcing to represent energy fluxes to the snowpack, as modulated primarily by varying cloud cover. Here, the instantaneous MODDRFS estimate is used as a tie point to calculate temporally resolved surface radiative forcing. Dust radiative forcing scenarios were considered for 1) clear-sky conditions and 2) all-sky conditions using satellite-based cloud observations. Comparisons against in situ stations in the Rocky Mountains show that accounting for the temporally resolved all-sky solar irradiance via satellite retrievals yields a more representative time series of dust radiative effects compared to the clear-sky assumption. The modeled impact of dust on enhanced snowmelt was found to be significant, accounting for nearly 50% of the total melt at the more contaminated station sites. The algorithm is applicable to regional basins worldwide, bearing relevance to both climate process research and the operational management of water resources.

A posteriori clear-sky identification methods in solar irradiance time series: Review and preliminary validation using sky imagers

2019 ◽  
Vol 109 ◽  
pp. 412-427 ◽  
Author(s):  
Christian A. Gueymard ◽  
Jamie M. Bright ◽  
David Lingfors ◽  
Aron Habte ◽  
Manajit Sengupta
Keyword(s):  
Time Series ◽  
Solar Irradiance ◽  
A Posteriori ◽  
Identification Methods ◽  
Clear Sky ◽  
Preliminary Validation

scholarly journals Performance of a Pebble Bed Thermal Storage Integrated with Concentrating Parabolic Solar Collector for Cooking

2019 ◽  
Vol 2019 ◽  
pp. 1-12
Author(s):  
Dejene Kebede Kedida ◽  
Demiss Alemu Amibe ◽  
Yilma Tadesse Birhane
Keyword(s):  
Forced Convection ◽  
Solar Irradiance ◽  
Storage Capacity ◽  
Addis Ababa ◽  
Thermal Storage ◽  
Storage Efficiency ◽  
Pebble Bed ◽  
Clear Sky ◽  
Tropical Areas ◽  
Green Solution

Cooking using biomass, which is commonly practiced in developing countries, causes rampant deforestation and exposure to emission. Hence, utilization of solar energy for cooking is a green solution. As solar radiation is not available at every hour of the day, thermal storage is essential for availing thermal energy at required time of use. Therefore, this work investigates the efficiency of solar cooker with parabolic concentrating collector integrated with thermal storage using 1D finite difference computational model. A cook stove on packed pebble bed thermal storage having 0.3 m diameter and 0.9 m height and a storage capacity of 40.1 MJ of energy during a clear day and 12.85 MJ energy was simulated for charging and discharging (cooking), under Addis Ababa climatic condition for days, with highest and lowest solar irradiance and thermal storage efficiency of 66.7%, cooker thermal efficiency of 45% during discharging of heat by forced convection, and 41% during discharging of heat by conduction, were obtained for the day with the highest solar irradiance. The overall efficiency of the cook stove with thermal storage was 30% and 22% for discharging by forced convection and conduction, respectively. For the day with lowest beam solar irradiance, the storage, thermal and overall efficiencies were 70.9%, 31.1% and 22.0%, respectively. Hence, it can be concluded that solar concentrating cookers with thermal storage can have an overall cooking efficiency between 22% and 30% on a clear sky day when the Sun is overhead in tropical areas.

Field measurement of clear-sky solar irradiance in Badain Jaran Desert of Northwestern China

2013 ◽  
Vol 122 ◽  
pp. 194-207 ◽  
Author(s):  
Jianrong Bi ◽  
Jianping Huang ◽  
Qiang Fu ◽  
Jinming Ge ◽  
Jinsen Shi ◽  
...  
Keyword(s):  
Field Measurement ◽  
Solar Irradiance ◽  
Northwestern China ◽  
Badain Jaran Desert ◽  
Clear Sky
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