Boundary-Layer Meteorology

, Volume 99, Issue 1, pp 127–150

Sonic Anemometer Tilt Correction Algorithms

  • James M. Wilczak
  • Steven P. Oncley
  • Steven A. Stage
Article

Abstract

The sensitivity of sonic anemometer-derived stress estimates to the tilt of the anemometer is investigated. The largest stress errors are shown to occur for unstable stratification (z/L<0) and deep convective boundary layers. Three methods for determining the tilt angles relative to a mean streamline coordinate system and for computing the tilt-corrected stresses are then compared. The most commonly used method, involving a double rotation of the anemometers' axes, is shown to result in significant run-to-run stress errors due to the sampling uncertainty of the mean vertical velocity. An alternative method, requiring a triple rotation of the anemometer axes, is shown to result in even greater run-to-run stress errors due to the combined sampling errors of the mean vertical velocity and the cross-wind stress. For measurements over the sea where the cross-stream stress is important, the double rotation method is shown to overestimate the surface stress, due to the uncorrected lateral tilt component. A third method, using a planar fit technique, isshown to reduce the run-to-run stress errors due to sampling effects, and provides an unbiased estimate of the lateral stress.

Anemometers Coordinate systems Sloping terrain Surface layer Tilt corrections 

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Copyright information

© Kluwer Academic Publishers 2001

Authors and Affiliations

  • James M. Wilczak
    • 1
  • Steven P. Oncley
    • 2
  • Steven A. Stage
    • 3
  1. 1.Environmental Research Laboratories, Environmental Technology LaboratoryNational Oceanic and Atmospheric AdministrationBoulderUSA
  2. 2.National Center for Atmospheric ResearchBoulderUSA
  3. 3.nnovative Emergency ManagementBaton RougeUSA

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