Estimates of Horizontal Advection Using Field Measurements in a Crop Canopy

An intensive field experiment was performed on the UC Davis agricultural fields in which we estimated the effects of horizontal advection as a function of distance from the edge of a plant canopy. Turbulence data including water vapor, wind speeds, and temperature were measured above the canopy at three different distances downwind from the edge and at one location over the bare soil upwind of the canopy. Fast response wind speed and temperature were also measured within the canopy at the same three locations within the crop. An array of twenty carefully cross-calibrated temperature and relative humidity sensors were placed at four heights at five different locations outside and within the canopy. From this data vertical fluxes of sensible heat were calculated within and above the canopy at the different distances from the edge and vertical fluxes of water vapor were calculated at the different locations above the canopy. Horizontal advection of heat and water vapor was also calculated at different distances into the canopy. The effects of horizontal advection and its magnitude with respect to vertical fluxes were quantified at varying distances from the edge. This data is used to validate the UC Davis K-theory and higher-order closure models of horizontal advection inside canopies. In addition energy budget closure was examined as a function of distance from the edge.