Article

Boundary-Layer Meteorology

, Volume 112, Issue 3, pp 503-523

First online:

A Simple Parameterisation for Flux Footprint Predictions

  • N. KljunAffiliated withInstitute for Atmospheric and Climate Science ETH
  • , P. CalancaAffiliated withSwiss Federal Research Station for Agroecology and Agriculture
  • , M. W. RotachAffiliated withInstitute for Atmospheric and Climate Science ETH
  • , H. P. SchmidAffiliated withDepartment of Geography

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Abstract

Flux footprint functions estimate the location and relative importance of passive scalar sources influencing flux measurements at a given receptor height. These footprint estimates strongly vary in size, depending on receptor height, atmospheric stability, and surface roughness. Reliable footprint calculations from, e.g., Lagrangian stochastic models or large-eddy simulations are computationally expensive and cannot readily be computed for long-term observational programs. To facilitate more accessible footprint estimates, a scaling procedure is introduced for flux footprint functions over a range of stratifications from convective to stable, and receptor heights ranging from near the surface to the middle of the boundary layer. It is shown that, when applying this scaling procedure, footprint estimates collapse to an ensemble of similar curves. A simple parameterisation for the scaled footprint estimates is presented. This parameterisation accounts for the influence of the roughness length on the footprint and allows for a quick but precise algebraic footprint estimation.

Boundary-layer scaling Boundary-layer stability Fetch Flux footprint Lagrangian stochastic particle dispersion model Parameterisation