Modeling and Prediction of Clear-Sky Solar Irradiance Losses Using Meteorological and Radiative Parameters: A Case Study in Ouarzazate, Morocco
Abdelali ABDESSADAK, Hicham GHENNIOUI, Nadège THIRION-MOREAU, Mounir ABRAIM, Safae MERZOUK, Brahim ELBHIRI
Abstract. Understanding how to quantify loss potential due to clear-sky solar irradiance is essential for the development of enhanced Photovoltaic and Solar Energy Forecasting systems in Semi-Arid climates. In Ouarzazate, Morocco, four years (2021 – 2024) of daily weather and solar radiation observations collected by satellite and from the ground were analysed in this research through the analysis of clear-sky losses. Clear-sky conditions were isolated from all others by applying a Clearness Index threshold of ≥0.65 (KT), and Clear-sky Losses were derived from the relative differentials between All-Sky Shortwave Solar Irradiance (SSI) and Clear-Sky Shortwave Solar Irradiance (SSI). Correlation analysis between the Clear-Sky Loss and four key weather variables produced strong correlations. Three models were created to predict clear-sky losses: Linear Regression (LR), Second Order Polynomial Regression (2PR), and a Random Forest (RF) algorithm. The results indicated that the 2PR model provided the best fit (R² = 0.9965, RMSE = 0.0079) allowing for accurate comparisons of the 2PR model to the two better-known methods of predicting Solar Resource & Energy Potential.
Keywords
Clear-Sky Irradiance, Irradiance Losses, Solar Radiation, Solar Energy Forecasting, Clearness Index
Published online 4/25/2026, 8 pages
Copyright © 2026 by the author(s)
Published under license by Materials Research Forum LLC., Millersville PA, USA
Citation: Abdelali ABDESSADAK, Hicham GHENNIOUI, Nadège THIRION-MOREAU, Mounir ABRAIM, Safae MERZOUK, Brahim ELBHIRI, Modeling and Prediction of Clear-Sky Solar Irradiance Losses Using Meteorological and Radiative Parameters: A Case Study in Ouarzazate, Morocco, Materials Research Proceedings, Vol. 64, pp 148-155, 2026
DOI: https://doi.org/10.21741/9781644904091-18
The article was published as article 18 of the book Energy Futures
Content from this work may be used under the terms of the Creative Commons Attribution 3.0 license. Any further distribution of this work must maintain attribution to the author(s) and the title of the work, journal citation and DOI.
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