## 2 Materials and Methods  
### Study Area  
The study area is the Campania region, sited in Southern Italy, with an extension of about 14,000 km\({}^{2}\). Figure 1 shows the location of the region, bounded between the coastline of the Tyrrhenian Sea and the mountains of the Southern Apennines. The relief map, also displayed in Figure 1, reveals the topographic complexity of the study area, characterized by two main plains and by an irregular orography in proximity of the sea and in the inner part of the region, that highly influences the spatial variability of the weather [51]. The study area is characterized by Mediterranean climates with hot, dry summers, warm springs and mild, wet winters and autumns. Precipitations occur mostly in autumn and winter: the maximum monthly precipitations are recorded during November and December. Although the actual duration of the irrigation season is determined by the weather variability and specific agricultural practices, irrigation in open fields generally starts in April and it lasts until the end of September. Thus, hereinafter the period from April 1 st to September 30 th will be referred to as irrigation season. The region has been the focus area of several projects aiming at developing innovative technologies to support water resources management in agriculture, based on satellite remote sensing and numerical weather predictions [9; 12; 14; 52]. It is also the demonstrative area of the EU-Horizon2020 project, LANDSUPPORT ([[https://www.landsupport.eu/](https://www.landsupport.eu/)]([https://www.landsupport.eu/](https://www.landsupport.eu/))), aiming at identifying sustainable management practices in agriculture. A network of 18 automatic weather stations (AWSs) has been operating since 2008, recording hourly measurements of air temperature at 2 m, wind speed at 10 m, relative humidity at 2 m, global incoming solar radiation and barometric pressure. The locations of the stations are shown on the regional map in Figure 1, while details about their reference ID number, site name, elevation and coordinates are listed in Table 1. This network is managed by the Regional Hydrometeorological Service, as part of the larger hydrometeorological network, including additional 59 weather stations equipped with air temperature sensors at 2 m (Figure A1 in Appendix B). Figure 1: Study area and relief map of the region along with the ground weather station sites. Table 2 illustrates the mean and coefficient of variation of daily weather data recorded at the 18 AWSs during the irrigation seasons of years 2008-2018, assumed as focus period in this study. Mean air temperature, T, ranges between 17.85 \({}^{\circ}\)C and 23.50 \({}^{\circ}\)C with coefficients of variation (cv) from 0.19 to 0.30; wind speed, WS, ranges from 1.27 m s\({}^{-1}\) to 4.64 m s\({}^{-1}\) with cv from 0.23 to 0.47; solar radiation, RS, ranged from 224 W m\({}^{-2}\) to 269 W m\({}^{-2}\) with cv from 0.26 to 0.35. The daily vapor pressure deficit (VPD) was computed by using daily mean air relative humidity data and the daily maximum and minimum temperatures according to the FAO irrigation and drainage study No. 56 [15] (pp. 36-40). The VPD ranged from 0.63 kPa to 1.13 kPa with coefficients of variation from 0.43 to 0.83. \begin{table}
\begin{tabular}{c c c c c c c} \hline
**Station** & \multicolumn{2}{c}{**T (\({}^{\circ}\)C)**} & \multicolumn{2}{c}{**WS (m s\({}^{-1}\))**} & \multicolumn{2}{c}{**VPD (kPa)**} & \multicolumn{2}{c}{**RS (W m\({}^{-2}\))**} \\ \hline
**ID** & **Mean** & **cv** & **Mean** & **cv** & **Mean** & **cv** & **Mean** & **cv** \\ \hline  
\hline \end{tabular} T—air temperature; WS—wind speed; RS—solar radiation; VPD—vapor pressure deficit; cv—variation coefficient.  
\end{table} 
Table 2: Weather data statistics for the irrigation seasons (April–September) of years 2008–2018.