## 3 The Monte Scarpino Landfill and the SRS Test-Bed
### Reference Rainfall Measurements  
If global satellite remote sensing rainfall products are becoming more reliable and accurate as research and development efforts in this field advance, on the other hand, the today state-of-the-art literature suggests the use of RG and WR measurements to perform evaluation analysis of microwave links performances in measuring rain (see, e.g., in [33; 34; 35]). The motivation is that the RGs are characterized by very low uncertainties [2], especially when compared to remote sensing products [36], and are preferable to perform comparison over small areas [37]. Ground-based WRs represent another valuable standard system for this sort of comparative analysis as their maps provide a representation of rainfall fields with a 1 km spatial resolution and at 10 min time intervals. Even if such features are not fine enough to depict the time-space distribution of highly convective rainfall over small hydrologic basins, like the one considered in the Monte Scarpino landfill use case (torrent Chiaravagna catchment), the radar products constitute a valuable term of comparison for other rainfall map retrieval techniques.  
The rainfall measurements considered for analyzing and comparing the SRS results are provided by the Monte Gazzo tipping-bucket RG (characterized by a 0.2 mm rainfall sensitivity) and the Selex-Gematronik GPM250C C-band polarimetric radar, located on Monte Settepani (44\({}^{\circ}\)14\({}^{\circ}\)45.4\({}^{\prime\prime}\) N 8\({}^{\circ}\)11\({}^{\prime}\)50.5\({}^{\prime\prime}\) E) in the province of Savona, at a distance of about 57 km from the landfill. The radar and the RG are operated by the Environmental Protection Agency of the Liguria Region (ARPAL), and also by the Italian Department of Civil Protection.  
A multiparameter, multirelationship algorithm based on a decision tree is implemented in the Monte Settepani radar system and used for the estimation of rainfall intensity from measurements of polarimetric variables. For interested readers, a detailed description and validation of the algorithm used by the Monte Settepani radar can be found in [38]. The produced precipitation maps have spatial and temporal resolutions of \(1\times 1\) km\({}^{2}\) and 10 min, respectively. An example of a precipitation map is shown in Figure 6.  
To quantitatively evaluate the proposed estimation method against the aforementioned reference approaches, the following error measures are considered:  
\[\epsilon^{in}_{\{r,g\}} =E(\mathcal{R}-\mathcal{R}_{\{r,g\}}|t\in W) \tag{9}\] \[\epsilon^{out}_{\{r,g\}} =E(\mathcal{R}-\mathcal{R}_{\{r,g\}}|t\
otin W) \tag{10}\]  
where \(\mathcal{R}_{r}\) and \(\mathcal{R}_{g}\) are the rain intensities returned by the radar and the RG, respectively; \(E\) is the expectation operator; and \(W\) is the time window that strictly contains the rainfall.  
Figure 6: Example of precipitation map (**a**) provided by the GPM250C weather radar on 4 July 2018, at 03:50 UTC. The radar position is indicated by the central white dot. The area containing the Monte Scarpino landfill and the RG at Monte Gazzo is delimited by the white square, whose side length is about 50 km. A zoomed view of this area is provided in subfigure (**b**), where the red cross is centered on the landfill and the green plus sign indicates the RG.