Calibration and Tests of a Yaw Sphere-Thermometer System for Sensible Heat Flux Measurements

Abstract

A yaw sphere-thermometer assembly, to measure sensible heat flux density by the eddy correlation method, was built following the design of Tanner and Thurtell. Wind tunnel experiments indicate that the sphere constant should be 1.57, which is significantly less than the theoretical value of 2.25. The effects of tilt indicate that heat fluxes may be in error by 5% per degree of tilt In unstable conditions and up to 11% per degree in stable conditions. Field comparisons of the heat fluxes measured by the yaw sphere-thermometer system and a Bowen ratio apparatus produced satisfactory agreement.