## 4 Conclusions  
Comparisons between manual and automatic instruments for SD measurements were applied to the three synoptic stations (Larnaca A/P, Pafos A/P and Athalassa) where different sunshine devices are installed. The comparisons of daily SD are applied between four different types of instruments, namely the manual Campbell-Stokes sunshine recorders (CS), and automatic measurements based on pyranometers (Gl), pyrhilometer (Pr) and the CSD3 sunshine sensors. All sites show negative skewness of the daily SD values, and their monthly average daily sunshine durations range between 5 h/d (January) and 13.5 h/d (June or July). The average annual actual SD sum for all the sites is 3300 h, ranging from 3100 to 3500 h irrespective of the measuring device. Differences have been determined between the daily values measured with automatic sensors and the daily value of Campbell-Stokes sunshine recorder. The daily differences of the pairs of the sunshine recorders installed at the same location are mostly within the range of \(-\)1.0 to +1.0 h. However, in cases where the comparisons take place between the synoptic and the automatic weather stations, these differences are slightly higher. At Larnaca in the period 2009-2012, positive differences between the pyranometric method (Gl) and CS are observed during the summer months, while negative differences are observed during the winter months. Negative differences between Gl and CS are also observed almost throughout the year at Pafos during the period 2009-2012. The maximum positive difference for the period 2009-2012, for the Gl and CS pair is 2.5 h for Larnaca and 3 h for Pafos, whereas the lowest differences reached the values of \(-\)3.4 and \(-\)4.3 h, respectively. Comparing Pr with CS for the period 2012-2015 at Athalassa, the differences are mostly negative, and the maximum difference reached the value of 1.5 h, while the lowest difference was \(-\)4.4 h. The comparisons between CS recording devices and CSD3 sensors showed slightly higher ranges. For example, for the comparison of CS at Larnaca and CSD3 at Mennogia, the maximum difference is 4.5 h, and the lowest difference is \(-\)4.7 h. This is expected, since CSD3 measures the SD at AWSs which are located a short distance from the synoptic station, whereas the sky conditions are probably slightly different. Generally, the annual average daily differences between the different pairs range between 0.3 and 0.5 h, which are approximately 18 and 30 min. The main reason for larger values of manual sunshine duration is the 'overburning effect'. The burnt area on the card of the CS sunshine recorder does not cease immediately at the moment when a cloud disturbs the sunshine. This 'overburning' leads to an overestimation of sunny conditions, while the automatic instruments change faster in the direct solar radiation than the CS device. Generally, in all cases, the histograms of the differences resemble a normal distribution. The analysis of the differences showed that the pairs have approximately the same values in about 9% to 23% of all the measurements (Class C1). With the exception of the pair CSD3_Pent and CS, the percentage daily differences between the automatic sensors and CS recorders fluctuate between 48% and 59% within the range of \(-\)0.5 to 0.5 h i.e., between the \(-\)C2 and C2 classes. Generally, the frequencies of negative differences between the automatic and manual instruments are higher than the frequencies of positive differences for the pairs at Pafos and Athalassa. The highest negative percentage was 68% and it occurred at Pafos. In the case of Larnaca, the negative percentages of daily differences between the automatic instruments and the CS recorder range between 38% and 50%. The correlation between individual daily SD records is strong, as is indicated by the coefficient of determination (R\({}^{2}\)) which ranges between 0.84 and 0.96. The lowest correlation was recorded between the daily CS at Larnaca and CSD3 at Pentakomo.