Evaluation of a Bowen Ratio Measurement System over Forest and Clear-Cut Sites at Petawawa, Ontario

Abstract

This paper reports on the features of a reversing measurement system for the determination of the Bowen ratio. Ten-junction thermopiles are used to measure wet- and dry-bulb temperature differences, and a single thermocouple gives absolute wet-bulb temperature. The system is totally DC-powered and can be constructed to be portable. The performance of the system was evaluated in an experiment at the Petawawa National Forestry Institute, Chalk River, Ontario. The characteristics of the temperature gradients above a forest and a logged site are reported, along with the corresponding values of the Bowen ratio.