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Evaporation from sparse crops‐an energy combination theory
Author(s) -
Shuttleworth W. James,
Wallace J. S.
Publication year - 1985
Publication title -
quarterly journal of the royal meteorological society
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.744
H-Index - 143
eISSN - 1477-870X
pISSN - 0035-9009
DOI - 10.1002/qj.49711146910
Subject(s) - evaporation , aerodynamics , environmental science , canopy , sensitivity (control systems) , crop , simple (philosophy) , partition (number theory) , soil science , mathematics , agronomy , meteorology , thermodynamics , physics , ecology , engineering , combinatorics , electronic engineering , biology , philosophy , epistemology
A one‐dimensional model is adopted to describe the energy partition of sparse crops. Theoretical development of this model yields a combination equation which describes evaporation in terms of controlling resistances associated with the plants, and with the soil or water in which they are growing. the equation provides a simple but physically plausible description of the transition between bare substrate and a closed canopy. Although the aerodynamic transfer resistances for incomplete canopies have, as yet, no experimental justification, typical values, appropriate to a specimen agricultural crop and soil, are shown to have limited sensitivity in the model. Processes which require further study if the equation is to be used to calculate evaporation throughout a crop season are also discussed.