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Dew and thermal lag: A model for cocoa pods
Author(s) -
Monteith J. L.,
Butler D. R.
Publication year - 1979
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.49710544313
Subject(s) - sunrise , dew , dew point , environmental science , atmospheric sciences , condensation , wind speed , point of delivery , canopy , thermal , microclimate , meteorology , horticulture , physics , ecology , biology
Dew forms on cocoa pods after sunrise when the dew‐point temperature of air in the canopy rises faster than the surface temperature of the pods. Exchanges of heat and water vapour are estimated by treating a pod as an isothermal body with homogeneous thermal properties. Two treatments of this simple model are discussed. First, the heat balance equation is simplified to a form which allows the environmental limits for condensation to be derived explicitly. Second, the equation is solved numerically to find the duration and mean depth of wetness as a function of environmental variables. Consistent with observation, the thermal lag of the pod is about 1 to 3K; condensation to a depth of 10 to μm occurs when air at sunrise is almost saturated and windspeed is light. Condensation on cocoa pods is likely to be significant in the spread of Black Pod, a serious fungal disease.