## 4 Conclusions
The lower R\({}^{2}\) was obtained for the cases of comparisons of the sunshine recorders with the CSD3 sensors which are installed in the AWS close to the synoptic ones. A higher dispersion is observed in the middle of the graphs rather than towards the tops and bottoms of the regression lines. This can be attributed to the fact that on'mostly cloudy' (low daily sunshine duration) or'mostly clear' sunny (high daily SD) days, the instruments tend to measure similarsunshine durations. In contrast, under intermediate cloud conditions (middling daily sunshine durations), the SD measured by each instrument tends to be more dissimilar, due to the different sensitivity of each instrument. As is expected, the length of the prediction intervals for the cases of comparisons between CS sunshine recorders and CSD3 sensors is higher, due to the fact that the cloud appearance at the neighboring stations will probably be slightly different than those at the synoptic stations. The coefficients of determination for the regression equations under'mostly cloudy' and'mostly clear' conditions range between 0.53 and 0.86. The largest frequencies of negative differences between the electronic and manual devices were recorded under 'partly cloudy' sky conditions, and it can be attributed to the fact of the influence of the clouds which cover the solar disk in quick succession. Comparing statistically the different pairs using the Mann-Whitney nonparametric test which is the alternative parametric test to the Two-Sample T test, it was found that the medians are not statistically different. However, significant differences were only detected in the case of the pair of CS and Pr at Athalassa (2012-2015) using both tests. In the rest of the cases the differences are not statistically significant at the 5% significant level. The empirical coefficients of the Angstrom-Prescott (A-P) formulation for different pairs are very close. The parameter \(\alpha\) ranges from 0.227 to 0.298, while b varies from 0.468 to 0.533. The dispersion of the empirical values is small, since all the stations have almost the same climatic conditions. The coefficients of determination are very high, ranging from 0.728 to 0.907. The lowest values are obtained in the cases when the relative sunshine was measured by automatic stations equipped with CSD3 recorders. Otherwise, R\({}^{2}\) is around 0.90. It has to be noted that the empirical coefficients for the same location but in different time periods are almost similar. The daily direct horizontal irradiation is closely related to the daily sunshine duration through quadratic equations. The linear relationships between CS and the automatic sensors can be used to extend the time series of CS measurements. The slope of the trend line of the annual totals of SD for the whole period of measurements, in the case of Larnaca, it is positive, and it is statistically significantly different from zero at the 5% significant level. In contrast, the slopes at Pafos and Athalassa are negative, but they are not statistically significant from zero at the 5% significant level. The study could also be extended to compare the automatic sensors between themselves. Furthermore, satellite data can be compared with ground-based data. Conceptualization, S.P. ; Methodology, S.P. ; Investigation, S.P. ; Resources, A.P. ; Writing--original draft, S.P. ; Supervision, S.A.K. All authors have read and agreed to the published version of the manuscript. This research received no external funding. Not applicable. Restrictions apply to the availability of these data. Data was obtained from Meteorological Department of Cyprus and are available from [[http://www.moa.gov.cy/dom](http://www.moa.gov.cy/dom)]([http://www.moa.gov.cy/dom](http://www.moa.gov.cy/dom)) with the permission of Meteorological Department of Cyprus. The authors would like to thank the Meteorological Department of Cyprus for providing the meteorological data. The authors declare no conflict of interest.