An inter-comparison between Gill and Campbell sonic anemometers

• We inter-compared fluxes observed by CSAT3 and WindMaster sonic anemometers.
• A certain version of WindMaster (Pro) proved to require high frequency correction.
• Fluxes were nearly equal after angle of attack errors on WindMaster were corrected.

Inter-comparison measurements of the Gill WindMaster and Campbell CSAT3 ultrasonic anemometers were conducted in a burned black spruce forest in interior Alaska, in order to clarify the effects of correction to Gill sonic anemometer angle of attack errors on flux data comparison. A certain version of WindMaster (Pro) proved to require the correction of high-frequency signal loss in cospectra, due to the rolling average feature, resulting in a 6.5–14.2% increase in fluxes. Before the correction of angle of attack errors was applied to the WindMaster data, eddy fluxes measured by the WindMaster were 14.3–24.0% smaller than those from CSAT3. Applying this correction to WindMaster data, we found that the scalar fluxes measured by WindMaster and CSAT3 were nearly the same, while momentum flux was somewhat underestimated by WindMaster compared to CSAT3, even after corrected. Though the underestimation of fluxes by non-orthogonal sonic anemometers compared with orthogonal anemometers has been pointed out, and both WindMaster and CSAT3 are non-orthogonal, the inter-relationships of various types of sonic anemometers are still unclear. At this stage, therefore, our results may support the most reliable data comparisons between sites where Gill and Campbell CSAT3 anemometers are adopted by applying the correction of angle of attack errors to the data of Gill anemometers.