Flux Footprint - Examples of Real-field Flux Footprint Distribution

Examples of Real-field Flux Footprint Distribution

Degree to which flux footprint is affected by these factors is illustrated for the all three respective cases below on the example of actual evapotranspiration flux (ET) measured over prairie in summer time (Figures 3-5). Relative contribution of the land surface area to the flux for two different measurement heights at near-neutral stability is shown in Figure 3. Please note that not only distance to the peak contributing was affected by a measurement height, but magnitude of the peak and overall distribution of the footprint was dramatically affected as well. Below is an example of relative contribution of the land surface area to the flux for two different surface roughnesses at near-neutral stability (Figure 4). Area under the curves on the plot above and on the two plots below sums up to nearly 100% of the flux contribution. The remaining few percent of flux are coming from an area beyond 500 m. Example of the relative contribution of the land surface area to the flux for two different cases of thermal stability is shown below (Figure 5). This example is adopted from Leclerc, M.Y., and G.W. Thurtell (1990).