## 2 Literature Review  
[PERSON] et al. [11] validated the [PERSON] model [20] by comparing it to 1-min average GHI clear sky irradiance data in Benguerir (Green Energy Park, Morocco). The validation results are summarised in Table 1. The validation results showed that the [PERSON] model can accurately estimate clear sky GHI in the context of Benguerir's unique environment, where skies are frequently clear. The validation results were used as a basis of forecasting the 1-min GHI one day ahead. The study's challenge was not being able to do data quality control on observed GHI, which hindered the investigators from critically analysing the reasons for GHI overestimation. [PERSON] et al. [46] conducted a comparison study of observed and estimated GHI in Moroccan sites (Missour, Erfoud, Zagora, and Tantan). A comparison of the measured and estimated GHI revealed good agreement between them, and the results and quantifications are summarised in Table 1. However, these disparities were attributed to the consequence of the ground albedo, which was frequently present below the station's altitude due to the regular presence of clouds. [PERSON] et al. [47] evaluated the accuracy of five GHI clear sky models using 5-min interval data in Bourareah, Algeria and 10-min interval data in Ghardaia, the capital city of the Ghardaia Province in the northern-central region of Algeria in the Sahara Desert. The authors established that the European Solar Radiation Atlas (ESRA) [48; 49] and Ineichen-Perez [31] models performed the best with results as summarised in Table 1. The authors recommended that the two models be used as a foundation for renewable energy applications in the study area. [PERSON] et al. [50] verified 75 GHI clear sky irradiance measurements, revealing that different clear sky models provided varying results in each climatic area. They also discovered that certain models performed inconsistently in various climates due to an overdependence on input, and that some model coefficients were created using datasets from climates that were completely different from the climates in other areas where the models were used. [PERSON] and [PERSON] [51] assessed the accuracy of the three clear sky models ESRA [48; 49], Simplified Solis [29; 30], and Kasten [52; 53] by using data from five sites located in Uruguay and neighbouring countries (southeastern South America). The models chosen for evaluation were chosen based on the availability of relevant input data in the area. Clear sky conditions were automatically detected using [PERSON] et al. [54]'s methodology. There was a negative MBE across all models and locations, indicating that GHI was underestimated and the rRMSE values were good, as shown in Table 1. [PERSON] et al. [55] tested the accuracy of five clear sky models using one clear-sky day in Singapore. The models differed in performance, and the results were applied to build a new local model. [PERSON] [7] validated 8 clear sky GHI measurements across 20 sites using 16 independent input databases. The author found that Linke turbidity had the biggest influence on model dependability, and therefore that, rather than site-specific observed meteorological inputs, resulted in the models underestimating solar radiation. [PERSON] et al. [56] and [PERSON] et al. [57] carried out tests to validate very simple clear sky and cloudy sky GHI models under the conditions of Romania's climate and geographical latitudes (Eastern Europe). In July, the MAE of the clear sky models ranged between 7 and 14%, and in January, it ranged between 12 and 19%. [PERSON] and [PERSON] [58] evaluated three distinct models that were tailored for the study area's geographical location and used to estimate clear sky GHI at three places in Namibia's subtropical desert climate (Kokerboom, Arandis, and Auas). The models were considered based on the availability of their input requirements.