Articles
MODELING RADIATION TRANSMISSION, INTERCEPTION AND REFLECTION IN A HEDGEROW APPLE ORCHARD IN THE NORTHEASTERN PORTUGAL
Article number
584_7
Pages
73 – 80
Language
English
Abstract
Interception and absorption of radiation by discontinuous canopies of a well-watered and well-fertilized orchard determine the production of photo-assimilates.
Simple modeling approaches used for the simulation of extinction of radiation in homogeneous canopies, with leaves randomly distributed in space, are not applicable for discontinuous canopies.
The ideal descriptive model, from the standpoint of the radiative transfer processes, would have as inputs, detailed leaf and other element positions within the canopy and the leaf azimuth and angle from horizontal.
A practical model was constructed that minimizes the inputs on canopy structure and relies mostly on the geometry of the outer envelope of the canopy and assumes exponential extinction within it.
Inside this envelope the phytoelements can be considered as uniformly distributed or clumped.
The model simulates transmission, absorption and reflection of global radiation and photosynthetically active radiation in a hedgerow apple orchard.
Internally, it separates diffuse from direct radiation sources, and integrates instantaneous contributions to give the irradiance at any number of points across the rows, on the ground or at any point in the canopy envelope.
Scattering is accounted for, and the optical properties of the phytoelements and the soil can be changed.
Validation data were collected in an apple orchard in Northeastern Portugal.
Weather data were recorded continuously by an automated weather station.
Five tube solarimeters were laid out in different positions below the canopy to measure transmitted total radiation.
One pyranometer and two pyradiometers allowed continuous measurement of the downwelling and upwelling short and long wave radiative fluxes.
Ninety days of 10-minute data were used in the validation process.
The predicted and observed values were compared using both a daily and 10-minute time steps.
The model performance was good, making it suitable to be incorporated in more complex models, e. g., growth and production models.
Simple modeling approaches used for the simulation of extinction of radiation in homogeneous canopies, with leaves randomly distributed in space, are not applicable for discontinuous canopies.
The ideal descriptive model, from the standpoint of the radiative transfer processes, would have as inputs, detailed leaf and other element positions within the canopy and the leaf azimuth and angle from horizontal.
A practical model was constructed that minimizes the inputs on canopy structure and relies mostly on the geometry of the outer envelope of the canopy and assumes exponential extinction within it.
Inside this envelope the phytoelements can be considered as uniformly distributed or clumped.
The model simulates transmission, absorption and reflection of global radiation and photosynthetically active radiation in a hedgerow apple orchard.
Internally, it separates diffuse from direct radiation sources, and integrates instantaneous contributions to give the irradiance at any number of points across the rows, on the ground or at any point in the canopy envelope.
Scattering is accounted for, and the optical properties of the phytoelements and the soil can be changed.
Validation data were collected in an apple orchard in Northeastern Portugal.
Weather data were recorded continuously by an automated weather station.
Five tube solarimeters were laid out in different positions below the canopy to measure transmitted total radiation.
One pyranometer and two pyradiometers allowed continuous measurement of the downwelling and upwelling short and long wave radiative fluxes.
Ninety days of 10-minute data were used in the validation process.
The predicted and observed values were compared using both a daily and 10-minute time steps.
The model performance was good, making it suitable to be incorporated in more complex models, e. g., growth and production models.
Publication
Authors
P. De Melo-Abreu, R.L. Snyder, A.C. Ribeiro
Keywords
absorption of radiation, albedo, row orientation, model, Malus domestica.
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