## 3 Results and Discussions
### Displacements  
#### 3.3.1 PS-InSAR Displacements  
Interferograms, filtered with a Goldstein filter with a fixed window size (15 \(\times\) 15), were connected using the full-graph MBC method; thus, all possible connections between image pairs were considered (Figure 7). The full-graph MBC method produced both low and moderate-high coherence levels. Regarding the latter, six connections were characterised by coherences higher than 0.45, while 16 connections were characterised by coherences higher than 0.35. In order to obtain the maximum possible precision in interferometric processing, orbit parameterisation was based exclusively on the Precise Orbit Ephemerides (AUX_POEORB) provided by the Copernicus Sentinels POD Data Hub (2016). Among connections with high coherence \(\sim\)0.45, the pair 7-19 December 2015 shows the smallest normal baseline (\(\sim\)10 m), while the pair 22 June-16 July 2015 shows the highest normal baseline (\(\sim\)135 m), much smaller than the relevant critical baseline value, \(\sim\)1300-1600 m, depending on descending or ascending acquisitions, respectively. However, according to [PERSON] et al. (2017), baseline parameters were set smaller than 25% of the  
Figure 5: The temporal behaviour of the water surface temperature, \(T_{\text{W}}\) (K), retrieved by Landsat 8 data, using both 189-034 and 190-034 scenes. A sinusoidal interpolation curve (continuous dashed line) and a confidence band of \(\pm\)2 \(\times\)\(\sigma_{XY}\) between measured and interpolated values (dark grey lines) are reported to facilitate the interpretation of the phenomenon. Figure 6: The temporal behaviour of air temperature, \(T_{\text{A}}\) (K), measured in situ. A sinusoidal interpolation curve (continuous dashed line) and a confidence band of \(\pm\)2 \(\times\)\(\sigma_{XY}\) between measured and interpolated values (dark grey lines) are reported to facilitate the interpretation of the phenomenon. critical baselines. Since the acquisition of the 1 December 2016 is out of the study period, derived displacements were not compared to GNSS ones. The interferograms of the two InSAR pairs having coherence higher than \(\sim\)0.45 after applying the full-graph MBC method are shown (Figure 8, panel a). The water body pixels are characterised by low coherence, resulting in random phase differences. The \(x\)-axis represents the azimuth direction (in pixels), and the \(y\)-axis shows the range direction (in pixels). Figure 8: Panel (**a**): interferogram generated (in slant geometry) using the full-graph MBC method: pair 22 June–16 July 2015, normal baseline \(\sim\)135 m. The phase difference is represented between \(-\pi\) and \(+\pi\) using a rainbow colour ramp. Panel (**b**): High–quality Persistant Scatter (PS) obtained by processing the ascending dataset over-imposed an airborne orthophoto [80] (EPSG 6708) (red dots, selected PS on the dam to interpret the forcing–displacements phenomenon; white dots, remaining PS). Figure 7: Full-graph Multi-Baseline Construction (MBC) method: ascending dataset. Temporal-normal baselines are coloured using a rainbow scale according to the InSAR pair coherence. Many PS points are distributed over the dam and on the left bank with a high backscatter signal and a coherence higher than 0.7 (Figure 8, panel b). The full-graph MBC allowed them to be detected \(\approx\) 540 PSs (displayed in red). The objective of this research is to determine the dam displacements, not deformation, of the whole structure. PSs located over the DAM crest were then used for comparison with other data to interpret the forcing-displacements phenomenon. To this aim, displacements of selected PS over the dam have been spatially averaged to estimate a reference displacement of the dam. A one-month moving average was applied to highlight the trend of the displacement time series. The orthogonal displacements related to the water levels confirm a hysteresis-like loop during the emptying and filling periods of the dam (ibid.).