## 2 Materials and Methods
\begin{table}
\begin{tabular}{c c c c c c c c} \hline \hline \multirow{2}{*}{**Station**} & **Long.** & **Lat.** & \multirow{2}{*}{**Elev. (m)**} & **SunRecorder\_1** & **SunRecorder\_2** & **Period** & **Comparisons/Tests** \\  & **(deg)** & **(deg)** & & & & & \\ \hline Pafos A/P & 32.4833 & 34.7167 & 10 & CS & CM6B (GI) & 2009–2012 & CS vs. Gl \\ \hline Larnaca A/P & 33.6333 & 34.8833 & 1 & CS & CM6B (GI) & 2009–2012 & CS vs. Gl \\ Menogia (15 km) \({}^{1}\) & 33.4333 & 34.8500 & 140 & CSD3 & & 2009–2012 & CS vs. CSD3\_Men. \\ Pentakomo (35 km) & 33.2617 & 34.7076 & 23 & CSD3 & & 2011–2012 & CS vs. CSD3\_Pent. \\ \hline Athalassa & 33.4000 & 35.1500 & 158 & CS & CHP1 (Pr) & 2012–2015 & CS vs. Pr \\ \hline \hline \end{tabular} \({}^{1}\) Distance of AWS from the synoptic station.  
\end{table} 
Table 1: Coordinates of meteorological stations involved in simultaneous measurements of different methods of daily SD (CS = Campbell-Stokes sunshine recorder, GI = SD from global radiation (CM6 B pyranometers), Pr = SD from Kipp & Zonen CHP1 Pyrhiolimeter and CSD3 = SD from Kipp & Zonen automatic sensors), during the periods: 2009–2012 and 2012–2015. Furthermore, the measurements differ in their temporal resolution and precision. The manual measurements have a daily resolution, while the automatic measurements have a temporal resolution of ten minutes with precision of one minute. Only concurrent daily sunshine data from manual and automatic instruments were used for analyses at each location. For the estimation of daily sunshine total, all hourly data must be available for the given day. The sunshine data were then aggregated into monthly totals and the percentage difference of sunshine hours between the two instruments was calculated using the following equation:  
\[\%\;\text{Difference}=(\text{Daily SD of AD})-(\text{Daily SD of CS})\times 100/(\text{Daily SD of CS}) \tag{1}\]  
A negative percentage difference indicates that the automatic SD is lower than the manual CS recorder, while a positive percentage difference indicates that the automatic sensor measures higher SD compared to the CS recorder. It is expected that the automatic sensors would record higher sunshine duration than the CS instrument, due to the higher sensitivity and sampling frequency of the automatic instrument. On the other hand, SD from CS is obtained with sun cards which are interpreted by observers. Therefore, a certain level of subjectivity is inherent regarding these data, which can result in dissimilar SD estimates from different observers. Furthermore, at times of frequently passing clouds the electronic sensor may be able to correctly assess the short SD, while in those periods, the CS continues to burn a trace on the sun card. Additionally, the daily SD total may be entered into the climate database incorrectly. On the other hand, the automatic sensors could be a source of error if there are issues with calibrations or shading the sensors. Figure 1: Map of Cyprus showing the synoptic stations (Larnaca A/P, Pafos A/P and Athalassa) with parallel manual and automatic measurements of SD obtained either locally or from other neighbor AWS (Mennogia, Pentakomo) equipped with CSD3 sensors. The sky conditions are classified according to the clearness index. The daily clearness index (\(K_{T}\)) is defined as the ratio of the daily global irradiation (\(G_{d}\)) to the respective extraterrestrial irradiation (\(G_{0d}\)), both measured on horizontal surfaces:  
\[K_{T}=G_{d}/G_{0d} \tag{2}\]  
[PERSON] et al. [28] have proposed four sky conditions which are based on the relation between hourly irradiances of global, direct and diffuse radiation and the clearness index. The method was also implemented successfully at Athalassa by [PERSON] et al. [29]. The \(K_{T}\) ratio must be lower than 1. The four sky categories based on clearness index and relative sunshine duration (\(\sigma=S_{d}/S_{0d}\)) are defined as follows:  
Class I: Cloudy sky when \(K_{T}\leq 0.35\) or \(\sigma\leq 0.3\).