From AMS Glossary
A modeling approach to determine the relative importance of upwind source areas on the value of an atmospheric variable at a given height.
The footprint is dependent on atmospheric stability and the surface type and is different for scalars than for higher-order turbulence statistics (such as turbulent fluxes). Footprint models use either Eulerian or Lagrangian dispersion theory. The former is usually based on idealized assumptions (e.g., horizontal homogeneity, restriction of the vertical range), whereas the latter (stochastic particle modeling) may take into account more realistic situations but is computationally much more expensive.