Estimation of Sky Thermal Irradiance in Arid Climate under Clear Sky Conditions

The sky thermal irradiance ( R sky ) is an important factor in meteorological, climatic, and energy balance studies. There are several empirical models for predicting R sky ; however, these are based on the meteorological parameters measured in non-arid climatic conditions and an empirical model for...

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Bibliographic Details
Published in:International journal of thermophysics 2020, Vol.41 (6), Article 76
Main Authors: Ahmed, H. A., Yu-xin, T., Qi-chang, Y., Al-Helal, I. M., Shady, M. R., Abdel-Ghany, A. M.
Format: Article
Language:English
Subjects:
Air temperature
Arid regions
Atmospheric models
Classical Mechanics
Condensed Matter Physics
Equivalence
Geophysics
Industrial Chemistry/Chemical Engineering
Irradiance
Mathematical models
Meteorological parameters
Model accuracy
Physical Chemistry
Physics
Physics and Astronomy
Relative humidity
Solar radiation
Thermodynamics
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Summary:The sky thermal irradiance ( R sky ) is an important factor in meteorological, climatic, and energy balance studies. There are several empirical models for predicting R sky ; however, these are based on the meteorological parameters measured in non-arid climatic conditions and an empirical model for predicting R sky in arid climates is unavailable. Therefore, this study presents two empirical models for predicting the R sky under clear sky conditions, common in arid regions such as the Arabian Peninsula. One is based on the sky equivalent emissivity (ε sky -model) and the other on the sky equivalent temperature ( T sky -model). Meteorological parameters (i.e., air temperature, relative humidity, solar radiation, and downward R sky ) were measured over 3 years and used to develop and validate the proposed models. The results showed that the proposed ε sky - and T sky -models had the highest predictive accuracy with a coefficient of determination of 0.86 compared with previously published models. In addition, the proposed ε sky - and T sky -models resulted in low values of root mean square and mean absolute percentage errors (7.2 and 7.8 W·m −2 and 1, 2 %, respectively); they were able to precisely predict R sky at any time in a clear arid climate compared with the prohibitive and time-consuming measurements.
ISSN:0195-928X
1572-9567
DOI:10.1007/s10765-020-02656-1