Determining Reference Evapotranspiration in Greenhouses from External Climate
Abstract
Introduction
Materials and Methods
Sites
AUB Site
AREC Site
Equipment
Evapotranspiration Modeling
Penman-Monteith Evapotranspiration
Hargreaves-Samani Reference Evapotranspiration Calculations
Greenhouse Hargreaves Evapotranspiration Calculations
Calibration, Verification, and Validation
Calibration
Verification
Validation under Different Experimental Conditions
Statistical Analysis
Results and Discussion
Summary of Relationships between Greenhouse and Outdoor and Weather Variables
Parameter | AUB | AREC | ||||||
---|---|---|---|---|---|---|---|---|
Greenhouse (G) | Outdoor (O) | Mean % difference | O/G | Greenhouse (G) | Outdoor (O) | Mean % difference | O/G | |
Ventilated | ||||||||
(°C) | 34 | 30 | 13 | 1.13 | 33 | 33 | 0 | 0.99 |
(°C) | 24 | 22 | 9 | 1.08 | 14 | 15 | 0.92 | |
(°C) | 28 | 26 | 9 | 1.08 | 22 | 24 | 0.93 | |
(°C) | 10 | 8 | 29 | 1.26 | 19 | 18 | 6 | 1.05 |
(%) | 59 | 68 | 0.87 | 55 | 37 | 62 | 1.50 | |
() | 9.1 | 19.8 | 0.46 | 18.8 | 24 | 0.77 | ||
() | 2.4 | 3.9 | 0.61 | 3.6 | 5.8 | 0.62 | ||
() | 2.3 | 4.9 | 0.48 | 4.2 | 5.6 | 0.74 | ||
() | 2.6 | 4.5 | 0.58 | 5.6 | 6.4 | 0.86 | ||
Unventilated | ||||||||
(°C) | 36 | 21 | 76 | 1.72 | 32 | 25 | 29 | 1.29 |
(°C) | 16 | 12 | 28 | 1.26 | 10 | 10 | 0.99 | |
(°C) | 23 | 16 | 42 | 1.41 | 19 | 18 | 10 | 1.10 |
(°C) | 20 | 8 | 155 | 2.41 | 22 | 15 | 52 | 1.49 |
(%) | 56 | 70 | 0.80 | 49 | 51 | 0.96 | ||
() | 6.8 | 12.8 | 0.53 | 12.2 | 18.7 | 0.66 | ||
() | 1.5 | 2.0 | 0.72 | 2.0 | 3.7 | 0.54 | ||
() | 1.6 | 2.5 | 0.64 | 2.5 | 3.6 | 0.69 | ||
() | 2.6 | 2.9 | 0.90 | 4.4 | 3.9 | 14 | 1.13 |
Note: Mean % variable.
Greenhouse versus Outdoor and Other Variables
Ventilated Conditions
Process | Outdoor variable | RMSE | MAE | RE | |
---|---|---|---|---|---|
Ventilated case | |||||
Calibration (at AUB) () | Penman-Monteith () | 0.80 | 0.26 | 0.21 | 10.4 |
Hargreaves-Samani () | 0.82 | 0.25 | 0.20 | 9.7 | |
Hargreaves-Samani () | 0.61 | 0.37 | 0.30 | 14.4 | |
Measured solar radiation () | 0.91 | 0.18 | 0.15 | 7.1 | |
Computed solar radiation () | 0.69 | 0.33 | 0.27 | 12.9 | |
Verification (at AUB) () | Penman-Monteith () | 0.96 | 0.17 | 0.13 | 8.1 |
Hargreaves-Samani () | 0.97 | 0.22 | 0.18 | 10.4 | |
Hargreaves-Samani () | 0.90 | 0.20 | 0.16 | 9.8 | |
Measured solar radiation () | 0.97 | 0.13 | 0.10 | 6.4 | |
Computed solar radiation () | 0.88 | 0.22 | 0.17 | 10.4 | |
Validation (at AREC) () | Penman-Monteith () | 0.71 | 0.55 | 0.47 | 15.4 |
Hargreaves-Samani () | 0.92 | 0.93 | 0.86 | 26.1 | |
Hargreaves-Samani () | 0.60 | 0.53 | 0.44 | 15.0 | |
Measured solar radiation () | 0.88 | 0.80 | 0.73 | 22.3 | |
Computed solar radiation () | 0.62 | 0.37 | 0.30 | 10.4 | |
Unventilated case | |||||
Calibration (at AUB) () | Penman-Monteith () | 0.94 | 0.15 | 0.11 | 9.6 |
Hargreaves-Samani () | 0.93 | 0.15 | 0.11 | 9.8 | |
Hargreaves-Samani () | 0.78 | 0.27 | 0.20 | 18.0 | |
Measured solar radiation () | 0.92 | 0.16 | 0.12 | 10.5 | |
Computed solar radiation () | 0.75 | 0.29 | 0.22 | 19.1 | |
Verification (at AUB) () | Penman-Monteith () | 0.98 | 0.13 | 0.09 | 9.3 |
Hargreaves-Samani () | 0.99 | 0.10 | 0.07 | 7.1 | |
Hargreaves-Samani () | 0.88 | 0.29 | 0.18 | 21.1 | |
Measured solar radiation () | 0.98 | 0.10 | 0.07 | 7.7 | |
Computed solar radiation () | 0.89 | 0.27 | 0.18 | 19.8 | |
Validation (at AREC) () | Penman-Monteith () | 0.66 | 0.36 | 0.33 | 17.8 |
Hargreaves-Samani () | 0.92 | 0.11 | 0.10 | 5.7 | |
Hargreaves-Samani () | 0.63 | 0.14 | 0.11 | 7.3 | |
Measured solar radiation () | 0.85 | 0.10 | 0.09 | 5.1 | |
Computed solar radiation () | 0.57 | 0.16 | 0.13 | 8.1 |
Note: RMSE = root mean square error (); MAE = mean absolute error (); RE = relative error (%); and = number of observations.
Unventilated Conditions
Verification of the Modeling of Greenhouse from Outdoor
Validation and Generalization of Greenhouse Relationships with Outdoor Climate
Discussion
Penman-Monteith Results
Hargreaves-Samani Equation Results
Greenhouse Transmissivity
Site | Condition | Equation | RMSE | MAE | RE | ||
---|---|---|---|---|---|---|---|
AUB | Ventilated | Greenhouse | 249 | 0.86 | 0.218 | 0.169 | 8.6 |
AREC | Ventilated | Greenhouse | 47 | 0.81 | 0.253 | 0.193 | 7.1 |
AUB | Unventilated | Greenhouse | 144 | 0.81 | 0.249 | 0.214 | 16.5 |
AREC | Unventilated | Greenhouse | 19 | 0.80 | 0.082 | 0.053 | 4.1 |
Note: RMSE = root mean square error (); MAE = mean absolute error (); RE = relative error (%); and = number of observations.