Diploma Thesis

Auswertung von Turbulenzmessgerätevergleichen unter besonderer Berücksichtigung von EBEX-2000

Matthias Mauder (10/2001-03/2002)

Support: Thomas Foken

Objects of this investigation are five types of sonic anemometers that are widely used at pre-sent for turbulence measurements in the atmosphere. These are the CSAT3 (Campbell Scien-tific), Solent HS (Gill Instruments), the New UW-Probe (NCAR), USA-1 (Metek) and the Model 81000 (R.M. Young). The main focus of this work is on the processing of the EBEX-2000 field intercomparison. In order to complete the characterisation of the instruments re-sults of further intercomparison experiments are comparatively analysed. Additionally three types of sonic anemometers are examined in a wind tunnel study. Within the scope of the field intercomparison the parameters horizontal wind velocity, vari-ance of the vertical wind velocity, variance of the sonic temperature, friction velocity and buoyancy flux are calculated. In order to make the different instruments as comparable as possible the measurement data are Planar Fit transformed and Moore corrected for spectral losses because of averaging about different path lengths. The highest measurement quality was found for the CSAT3 and the New UW-Probe. Other types of anemometers show significant deviations from the reference especially for the meas-urement of fluctuations of the vertical wind component. This results in uncertainties in the determination of friction velocity and vertical exchange fluxes. The measured values of the USA-1 show a significant dependency on the wind direction that is probably caused by self correlation between the wind components. Though mean friction velocities of the Young 81000 are in good agreement with the reference because of a non documented internal correction, single measuring values show a bigger deviation.

last modified 2003-12-16