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.
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- de Haan, P. and Rotach, M. W.: 1998, ‘A Novel Approach to Atmospheric Dispersion Modelling: The Puff-Particle Model (PPM)’, Quart. J. Roy. Meteorol. Soc. 124, 2771–2792.Google Scholar
- Hanna, S. R., Chang, J. C., and Strimaitis, D. G.: 1993, ‘Hazardous Gas Model Evaluation with Field Observations’, Atmos. Environ. 27A, 2265–2281.Google Scholar
- Horst, T. W. and Weil, J. C.: 1994, ‘How Far is Far Enough?: The Fetch Requirements for Micrometeorological Measurement of Surface Fluxes’, J. Atmos. Ocean. Tech. 11, 1018–1025.Google Scholar
- Miyake, M.: 1965, Transformation of the Atmospheric Boundary Layer over Inhomogeneous Surfaces, Sci. Rep. 5R-6, University of Washington, Seattle, U.S.A.Google Scholar
- Raupach, M. R., Antonia, R. A., and Rajagopalan, S.: 1991, ‘Rough-Wall Turbulent Boundary Layers’, Appl. Mech. Rev. 44, 1–25.Google Scholar
- Rotach, M. W.: 2001b, ‘Urban-Scale Dispersion Modeling Taking into Account the Turbulence and Flow Characteristics of the Roughness Sublayer’, in 3rd International Symposium on Environmental Hydraulics, Tempe, AZ.Google Scholar
- Stull, R. B.: 1988, An Introduction to Boundary Layer Meteorology, Kluwer Academic Publishers, Dordrecht, 666 pp.Google Scholar
- Van Ulden, A. P.: 1978, ‘Simple Estimates for Vertical Diffusion from Sources near the Ground’, Atmos. Environ. 12, 2125–2129.Google Scholar
- Weil, J. C. and Horst, T. W.: 1992, ‘Footprint Estimates for Atmospheric Flux Measurements in the Convective Boundary Layer’, in S. Schartz and W. Slinn (eds.), Precipitation Scavening and Atmosphere-Surface Exchange, Vol. 2, pp. 717–728.Google Scholar