Assessment for aerodynamic and canopy resistances in simulating latent heat flux of Venlo-type greenhouse tomato

An accurate and dynamic evaluation of the latent heat flux (LE) of greenhouse crops is imperative for advancing precision irrigation. Previous studies used the Penman-Monteith model to evaluate LE and treated the canopy as a holistic leaf, overlooking the discrepancies in structure and microclimate across canopy vertical sections. This study divided the canopy into a shaded and a sunlit layer in line with the structural characteristics of the tomato canopy and the shift in solar elevation angle β. A full-layer model (PMI) and a semi-layer model (PMT) were established based on the layering difference in the evaluation of canopy resistance (rc) and aerodynamic resistance (ra). Eight models: PMI1, PMI2, PMI3, PMI4, PMT1, PMT2, PMT3, and PMT4, were obtained using meteorological data from 2 m above the ground and 2/3 of the canopy height in 2022 and 2023. The performance was compared with the big leaf model (PMB) and verified based on the LE measured by the lysimeter (LEm). The results indicated that LE had the highest sensitivity to canopy absorbed net radiation during the flowering stage (1≤LAI≤3), while PMI2 and PMI4 overestimated LE with the fitting slopes (LE-LEm) of 1.72 and 1.67 in 2022 and 1.70 and 1.55 in 2023, respectively. PMT3 and PMB underestimated LE; the fitting slopes in two years were both 0.83 and 0.80, respectively; PMI3 with the fitting slopes were 0.99 and 0.96 in two years, respectively. In the picking period (LAI≥5), LE was the most sensitive to vapor pressure deficit (VPD);PMI3 and PMB accurately simulated LE with the fitting slops, both over 0.9 in two years. Therefore, the canopy was layered when evaluating rc while treating it as a unit in evaluating ra, PMI3 showed the best comprehensive performance when simulating LE in different seasons and growth periods using meteorological data at 2 m above the ground.