## 2 Materials and Methods
### Field Data Collection
#### 2.5.1 Surface Heat Fluxes  
At the IIC site, a two-way NR-Lite and two four-way CNR1 net radiometers (Kipp and Zonen, Delft, The Netherlands) measured \(\mathrm{R_{n}}\) at the height of 3.3 m AGS. At the LIRF site, each of the three net radiometers was a two-way NR-Lite in 2020 and 2021. The CNR1 radiometer was installed on Field F (west station). NR-Lite radiometers measure net shortwave and longwave radiation within a spectral range from 0.2 to 100 \(\mathrm{\SIUnitSymbolMicro m}\), temperature dependency of 0.12%/\({}^{\circ}\)C, and a directional error of less than 30 W/m\({}^{2}\) at, at least, 1000 W/m\({}^{2}\)[46]. The CNR1 radiometer provides data regarding all four terms of the net radiation budget, and it has a measurement uncertainty that is within 10 to 35 \(\mathrm{\SIUnitSymbolMicro V}\)/W/m\({}^{2}\) and a directional error of 25 W/m\({}^{2}\) at 1000 W/m\({}^{2}\)[47]. Surface G data were determined using the soil heat flux plate method. At LIRF, two HFT3-L soil heat flux plates (Radiation and Energy Balance Inc., Bellevue, WA, USA) were buried at 0.08 m between and below maize rows at each measurement station. At the IIC site, the HFT3-L plates were placed between two consecutive maize rows due to the flooded furrow during irrigation events. One 5 TE soil water content sensor (Decagon Devices Inc., Pullman, WA, USA) was buried at 0.04 m. Two T107 temperature probes (Campbell Scientific Inc., Logan, UT, USA) were installed at 0.02 and 0.06 m below ground surface (BGS) to determine average soil temperature and for the calculation of soil heat storage above the 0.08 m soil layer from the HFT3-L plates. The HFT3-L sensors have thicknesses and diameters equal to 3.91 and 38.2 mm, respectively. The measurement uncertainty of soil heat flux from the plates is 5% [48]. Measured LE and H data were produced from acquired high-frequency wind speed, air temperature, and water vapor measurements using an eddy covariance (EC) system installed at each research site. At the IIC (Figure 5a), the EC system consisted of an LI-7500A open-path \(\mathrm{CO_{2}}\)/\(\mathrm{H_{2}O}\) gas analyzer (LI-COR Biosciences, Lincoln, NE, USA) and a CSAT three-dimensional (3D) sonic anemometer (Campbell Scientific Inc., Logan, UT, USA). At \begin{table}
\begin{tabular}{c c c} \hline \hline  & **USD—ARS** & **CSU Drone Center** \\ \hline UAS Unit & DJI S900 & DJI M600 \\ \hline Flight Altitude (m) & 120 & 100 \\ \hline UAS Speed (m/s) & 5 & 5 \\ \hline Temporal Resolution & Weekly & Weekly \\ \hline Imagery Pixel Size (m) & 0.03 & 0.08 \\ \hline Overlap/Sidelap Percentage (\%) & 88/70 & 80/70 \\ \hline Calibrated Reflectance Panel & Yes & Yes \\ \hline Orthorectified Coordinate System & WGS84 UTM & WGS84 UTM \\ \hline Post-processing Imagery Software & Agisoft Metashape & Pix4D v4.5.6 \\ \hline \hline \end{tabular}
\end{table} 
Table 7: The UAS mission summary for the USDA-ARS and CSU Drone Center at all sites. LIRF (Figure 5b), an LI-7500 DS open-path gas analyzer (LI-COR Biosciences, Lincoln, NE, USA) and a Gill WindMaster three-dimensional (3D) sonic anemometer (Gill Instruments, Lymington, Hampshire, UK) provided measurements of LE and H, respectively. Both EC systems at LIRF and IIC were installed at 3.5 m AGS, positioned facing the prevailing wind direction at each site (135\({}^{\circ}\) azimuth angle), and set to a sampling frequency equal to 10 Hz. The EC turbulent fluxes and respective ancillary data were recorded as 15-min and half-hour averages at the IIC and LIRF sites, respectively. The EC system often provides imbalanced turbulent fluxes regarding SEB closure [49; 50; 51], with the closure SEB ratio \"(H + LE)/(R\({}_{\rm n}\) - G)\" ranging from 70 to 90% [52; 53]. To improve the representativeness of H, LE, and ET\({}_{\rm a}\) measurements from the EC system, the residual-LE closure approach was chosen in this study to ensure the closure of the surface heat fluxes.