Eddy correlation flux measurements: The sediment surface area that contributes to the flux

• DOI: 10.4319/lo.2007.52.4.1672
• Publication Date: 2011-01-09T09:53:49Z
• Authors: Peter Berg; Hans Røy; Patricia L. Wiberg
• Keywords: TRACER

We investigated the size and shape of area on sediment surface, so‐called footprint, that contributes to flux in subaqueous eddy correlation measurements. Tracer tracking simulations were performed for a dissolved conservative tracer released from surface into current‐driven flow not affected by density stratifications waves. Simulations revealed footprint length ( l ) can be calculated as = −2.783 − 158.7 h + 159.2 2 120.8 log( z 0 (all units m) measurements heights between 0.05 0.3 m above roughness parameter values 7.04 × 10 −6 0.01 m. The upstream distance x max location strongest signal likewise estimated −0.09888 11.53 10.25 ‐ 6.650 log ). Because vertical turbulent mixing scales with mean current velocity, are independent velocity. width w 6.531 . These expressions developed water depths H > 27 In depth interval 6.7 , multiplying length, given above, factor 1 8.347exp(−0.2453 / ), whereas is For transfer rate over air‐water interface controls footprint. All valid isotropic turbulence, but first‐order estimate, also hold anisotropic conditions. contrast, √( E y /E where transverse diffusivity, respectively. Finally, we describe how site‐specific levels anisotropy near‐bottom extracted directly