Identifying sources and sinks of scalars in a corn canopy with inverse Lagrangian dispersion analysis I. Heat

Sources and sinks of heat in the canopy of a dense corn crop (LAI similar t o 5) were inferred through an inverse Lagrangian dispersion analysis. Input data were the profiles of air temperature and turbulence above and within the canopy. The analysis was verified in part by comparing its predictions of the net exchanges of sensible heat between canopy and air with direct me asurements of the sensible heat flux above the crop made by eddy correlatio n. Almost all the heat exchange occurred in the top half of the canopy, which was a strong heat source. The bottom half was a weak sink, virtually neutra l in the overall heat exchange. The net exchanges of heat predicted by the analysis were, on average, 21% higher than the eddy correlation heat fluxes , but exhibited identical time trends. It is concluded that the inverse Lag rangian technique leads to robust and qualitatively correct predictions of the heat flux and that the analysis scheme employed offers a relatively sim ple means for calculating scalar fluxes in plant canopies. (C) 2000 Elsevie r Science B.V. All rights reserved.