Comparative Study of Four Shadow Band Diffuse Irradiance Correction Algorithms for Almerı´a, Spain

López, Gabriel; Muneer, Tariq; Claywell, Randall

doi:10.1115/1.1666895

Cited by 10 publications

(5 citation statements)

References 16 publications

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“…Data from the CM3 under the shadowband were adjusted to represent all-sky diffuse radiation using the method of Muneer and Zhang (2002), reported as the most accurate of four commonly used algorithms when assessed using data from Spain (Lopez et al, 2004b), Israel and the UK (Lopez et al, 2004a). These data correlated well with the BF3 diffuse measurement (r = 0.99), but the BF3 overestimated by 10.7% and was therefore corrected by dividing by 1.107 before modelling.…”

Section: Appendix C Sensor Calibrationmentioning

confidence: 99%

Data-driven modelling of shortwave radiation transfer to snow through boreal birch and conifer canopies

et al. 2013

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Hydrological and land surface models require simple but accurate methods to predict the solar radiation transmitted through vegetation to snow, backed up by direct comparisons to data. Twenty shortwave pyranometers were deployed in forest plots of varying canopy structures and densities in sparse birch forest near Abisko, Sweden, in spring 2011 and mixed conifer forest near Sodankylä, Finland, in spring 2012. Above‐canopy global and diffuse shortwave irradiances were also measured. These data were used to test a model that uses hemispherical photographs to explicitly estimate both diffuse radiation and direct beam transmission, as well as two models that apply bulk canopy parameters and versions of Beers Law. All three models predict canopy shortwave transmission similarly well for leafless birch forest, but for conifers, the bulk methods perform poorly. In addition, an existing model of multiple reflections between canopy and snow was found to be suitable for birch, but not conifers. A new bulk approach based on empirical relationships with hemisphere‐averaged sky view fraction showed improved performance for both sites; this suggests benefits of avoiding the use of plant area index calculated from optical methods, which can introduce errors. Furthermore, tests using common empirical diffuse radiation models were shown to underestimate shortwave transmission by up to 7% relative to using the data, suggesting that new diffuse models are required for high latitudes. Copyright © 2013 John Wiley & Sons, Ltd.

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Section: Appendix C Sensor Calibrationmentioning

confidence: 99%

Data-driven modelling of shortwave radiation transfer to snow through boreal birch and conifer canopies

et al. 2013

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“…The shadow band for R S had a radius and width of 318 and 75 mm, respectively, and the shadow band for PAR had a radius and width of 80 and 13 mm, respectively. The shadow bands were adjusted each week for solar declination and corrected for diffuse irradiance obscured by the shadow band using the method of Muneer and Zhang (2002), which was found to have less error across a wide range of sky conditions than three other commonly used methods (López et al, 2004). Direct beam components were derived as the difference between the total and diffuse components, and the NIR wavelengths were derived as the difference between the global and PAR wavelengths.…”

Section: Appendixmentioning

confidence: 99%

Radiation Model for Row Crops: I. Geometric View Factors and Parameter Optimization

et al. 2012

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Row crops with partial cover result in different radiation partitioning to the soil and canopy compared with full cover; however, methods to account for partial cover have not been adequately investigated. The objectives of this study were to: (i) develop geometric view factors to account for the spatial distribution of row crop vegetation; (ii) combine view factors with a widely used vegetation radiation balance model; and (iii) optimize three parameters required by the model that describe leaf angle, visible leaf absorption, and near‐infrared leaf absorption. Measurements of transmitted and reflected shortwave irradiance for corn (Zea mays L.), grain sorghum [Sorghum bicolor (L.) Moench], and cotton (Gossypium hirsutum L.) were used to optimize parameters and evaluate the model. View factors were derived by modeling the crop rows as elliptical hedgerows. The optimized ellipsoid leaf angle parameter, visible leaf absorption, and near‐infrared leaf absorption were 1.0, 0.85, and 0.20 for corn; 1.5, 0.82, and 0.20 for grain sorghum; and 3.0, 0.83, and 0.14 for cotton, respectively. Visible leaf absorption was similar for all crops. Near‐infrared leaf absorption was the same for corn and grain sorghum but less for cotton. The only parameter that changed for each crop species was leaf angle. The optimized parameters for corn and grain sorghum were within the range of values recommended in previous studies, and the leaf angle parameter for cotton agreed with a previous study of cotton leaf angles. All parameters were distinctly identifiable, and no parameter correlation was observed.

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“…[7] For the particular case of total solar diffuse radiation measured by pyranometers, i.e., diffuse radiation spectrally integrated throughout the whole solar interval (0.285-2.800 mm), several authors have proposed different correction models [Drummond, 1956;Steven, 1984;LeBaron et al, 1990;Batlles et al, 1995;Muneer and Zhang, 2002]. These models have been validated by comparison with experimental measurements at different locations [López et al, 2004a[López et al, , 2004bKudish and Evseev, 2008;Sánchez et al, 2012] and are widely accepted to provide accurate and reliable total solar irradiance values.…”

Section: Introductionmentioning

confidence: 99%

Shadow‐band correction for diffuse ultraviolet radiation measurements

2013

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[1] Although the correction of shadow-band solar total diffuse measurements has been extensively studied, the case of diffuse ultraviolet measurements has not been properly addressed. This study analyzes the correction factor to be applied to experimental measurements performed adapting a shadow-band to a UV radiometer at a radiometric station in Badajoz (Spain). Three different models, based on approaches widely used for correcting total diffuse measurements, have been revised and adapted for the ultraviolet spectral range. Results reveal that some aspects of the correction proposed for total diffuse radiation are not suitable for ultraviolet diffuse radiation. The mathematical expressions are consequently modified to match the behavior in the ultraviolet range. Thus, three correction models particularized for ultraviolet diffuse measurements are proposed and validated against experimental data. The two models adapted from the original expressions proposed by Battles et al., and Steven show the best performance, with rRMSE of 2.74% and 2.20% and rMBE of 1.53% and 0.46%, respectively.Citation: Sa´nchez, G., A. Serrano, and M. L. Cancillo (2013), Shadow-band correction for diffuse ultraviolet radiation measurements,

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Comparative Study of Four Shadow Band Diffuse Irradiance Correction Algorithms for Almerı´a, Spain

Cited by 10 publications

References 16 publications

Data-driven modelling of shortwave radiation transfer to snow through boreal birch and conifer canopies

Data-driven modelling of shortwave radiation transfer to snow through boreal birch and conifer canopies

Radiation Model for Row Crops: I. Geometric View Factors and Parameter Optimization

Shadow‐band correction for diffuse ultraviolet radiation measurements

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