Footprint for Surface Fluxes: Concept and Assessment Methods

The area of turbulent flux formation or the coverage zone when measuring from masts is subject to spatial and temporal variability. The need for accurately assessing the flux formation area or footprint has significantly increased with the establishment of long-term monitoring stations for turbulent exchange over forests and other heterogeneous landscapes and the creation of observation networks to assess the intensity of matter and energy exchange between ecosystems and the atmosphere (e.g., FLUXNET, AsiaFlux, RuFlux). The footprint plays a crucial role in optimizing instrument placement, interpreting time series of measured fluxes, analyzing the variability of fluxes in response to changes in the underlying surface, and evaluating the quality of the data collected. However, estimating the footprint is challenging due to the diversity of the studied substances’ fluxes and concentrations. This article provides an overview of the available modeling methods for footprints, discussing their advantages and disadvantages. It also identifies current challenges and suggests ways to improve existing approaches.