44 Correction of Gill ultrasonic anemometer angle of attack errors under turbulent conditions and comparison with Campbell CSAT3

Wednesday, 30 May 2012
Rooftop Ballroom (Omni Parker House)
Taro Nakai, University of Alaska Fairbanks, Fairbanks, AK; and K. Shimoyama, H. Iwata, and Y. Harazono

When conducting field experiments using five Gill WindMaster ultrasonic anemometers, angle of attack errors of the Gill ultrasonic anemometers were confirmed to occur even under natural turbulent conditions. Based on this calibration, correction functions were newly obtained for these errors under turbulent conditions, functions which were somewhat different from those previously obtained from wind-tunnel data. Applying the new correction, eddy fluxes increased significantly even over meadow.

From the inter-comparison measurements of Gill WindMaster and Campbell CSAT3 ultrasonic anemometers, eddy fluxes measured by the WindMaster were significantly smaller than those by CSAT3, but these fluxes became almost equal when the new correction of angle of attack errors was applied to the WindMaster data. Though this result does not necessarily assure the accuracy of CSAT3, it is worth noting that reliable data comparisons can be made between sites where Gill anemometers and Campbel CSAT3 anemometers are adopted, by applying the new correction of angle of attack errors to the Gill anemometer.

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