## 2 Materials and Methods  
The geographical coordinates of the stations involved in the sunshine duration (SD) measurements using different methods and their period of measurements are presented in Table 1, while the locations are also shown in Figure 1. As is indicated by Table 1, daily data from five stations are used. The availability of data varies between 2 and 4 years in each period of measurements. The stations cover the southern coastal and inland plain areas of the island. The comparison tests are applied for the three synoptic stations (Larnaca A/P, Pafos A/P and Athalassa) where different sunshine devices are installed (manual and automatic). The manual measurements of SD are carried out by the Campbell-Stokes sunshine recorders (CS), while the automatic measurements at the synoptic stations are based on the Kipp & Zonen pyranometers (CM6B) and CHP1 pyrheliometer. Additionally, parallel measurements are also carried out by the Kipp & Zonen CSD3 sunshine recorders obtained from two automatic weather stations (AWSs) which are close to the synoptic station of Larnaca A/P. Since the distance between the synoptic and the AWSs is lower than 35 km, it is possible to assess the CSD3 sensors against the manual devices. Essentially, the comparisons of daily SD are applied between four different types of instruments, namely the manual Campbell-Stokes sunshine recorders (CS), and the automatic measurements based on pyranometers (GI), pyrhiolimeter (Pr) and the CSD3 sunshine sensors. Simultaneous records of SD have been obtained between 2009 and 2012 at two locations (Pafos A/P and Larnaca A/P). The SD measurements are based on CS sunshine recorders and Kipp & Zonen CM6 B pyranometers, as well as on Kipp & Zonen CSD3 SD sensors obtained from nearby stations such as Memogia and Pentakomo which are located at a distance of about 15 km and 35 km from Larnaca A/P, respectively. The selected stations have the same climatic conditions. The second period of simultaneous SD measurements represents the period 2012-2015 with records obtained from CS sensors and a Kipp & Zonen CHP1 pyrhiolimeter which was installed on a solar tracker system at Athalassa. The SD values obtained from manual and automatic sunshine recorders are, in some cases, different as a result of the different principles and technology adopted by these instruments [11; 12; 15; 24]. The sensitivity threshold of burning the card in the Campbell-Stokes recorder (CS) ranges from 70 to 280 W/m\({}^{2}\)[12]. The pyranometric method is based on the mean, minimum and maximum values of measured global irradiance over 10 min intervals. For this purpose, different algorithms were developed [16]. The CHP1 pyrheliometer is mounted on a solar tracker system and is a high-precision instrument designed to measure direct normal irradiance from the solar disk within a solid angle of 5\({}^{\circ}\). It uses a thermopile as a detector to measure the irradiance in the range of 280-4000 nm [27]. The threshold for the determination of SD is 120 W/m\({}^{2}\), which is recommended by WMO [5]. The CSD3 SD sensor measures SD through a high-quality glass tube and uses these photodiodes with a spectral response range from 400 to 1100 nm. One photo-diode measures the total radiation, while the other one measures scattered radiation. The threshold for the determination of SD of CSD3 is 120 W/m\({}^{2}\). As is indicated in Table 1, comparison tests are applied between the four methods of measurements (CS, pyranometric (GI), pyrheliometric (Pr) and CSD3) in order to determine whether the differences of the mean or median daily values are significant.