## 6 Discussions  
According to Table 2, Table 6, and Figures 3-5, there was no significant variation in model performance between sites with different humidity content, number of clear-sky days per year, and annual water vapour content. However, there was a notable variation when considering Tantan, the station with the lowest latitude 28.437 (\({}^{\circ}\) N), and Tangier, the station with the highest latitude 35.733 (\({}^{\circ}\) N). The differences were as follows: from Figure 3, when comparing these two sites with extreme latitudes, all the clear sky models underestimated GHI at the Tangier station as shown by negative rMBE values, and it is also noted that small values of rMBE less than \(-\)10% were reported with the exception of the ABCG model (\(-\)11.9%). At the Tantan station, except for the ABCG model (3.4%), positive large rMBE values greater than +10% were observed. This means that the ABCG model, a simple clear sky model that only depends on the sun's zenith angle, performed well at low-latitude sites, while the other models considered in the study performed well at high-latitude sites. [PERSON] et al. [105] also discovered a substantial fluctuation in solar radiation with latitude in Saudi Arabia, and after dividing the study region [15-55 (\({}^{\circ}\)S)] into 5\({}^{\circ}\) intervals, they reported the best tilt angles to be 20 (\({}^{\circ}\) S), 25 (\({}^{\circ}\) S), and 30 (\({}^{\circ}\) S), depending on the location.  
When comparing rMAE and rRMSE at these two sites, the Tantan station performed poorly, with both rMAE and rRMSE values greater than 10% in all models except for ABCG, whereas the Tangier station performed well, with both rMAE and rRMSE values less than 10% in all models except for ABCG.  
When considering coefficient of determination (R\({}^{2}\)), all clear sky models at Tangier had R\({}^{2}\) greater than 0.988, whereas all clear sky models at Tantan had R\({}^{2}\) less than 0.977. This demonstrates that latitude affects the performance of clear sky models, with high latitude favouring the ABCG clear sky model and low latitude favouring complex models. It was also observed that, overall, complex models outperformed simple clear sky models.  
The SOLCAST satellite-based dataset had a comparable performance with complex clear sky models, and it performed better than simple clear sky models except in two locations with extreme altitudes, Tantan (45 m) and Ouarzazate (1140 m), where it showed poor performance, indicating that SOLCAST performs poorly at both very high and very low altitudes. Overall, SOLCAST and ERA5 cloud cover can be used together as an accurate clear sky model in areas where complex clear sky models do not have inputs.  
McClear is not a perfect model and may introduce some bias that affects validation results in some areas, even though its inputs are high resolution and it has demonstrated excellent performance in various studies around the world. Another study limitation was the lack of reference observation GHI data to validate the clear sky models. Using reference data, future studies will validate models, particularly McClear. Another limitation was the lack of hourly aerosol data, so 3-h aerosols from CAMS AOD had to be interpolated. AOD 380 nm, 700 nm, and 500 nm were unavailable, and the AOD at 1240 nm had to be derived and interpolated; this could have influenced the results.  
Even though [27,101] discovered that ozone does not vary much over time and has a low influence on GHI, using monthly averages may introduce some bias. High spatial and temporal resolution model inputs are necessary to fully assess the performance of the clear sky model. To solve this challenge, meteorological institutions collecting observations should also record these critical meteorological parameters (albedo, ozone, water vapour, Linke turbidity, cloud cover, and aerosols).