Performance Evaluation of an Innovative Sampling System for Closed Path Eddy Covariance Measurements

A well-designed closed-path eddy covariance system has good frequency response, low maintenance and performs well in a wide variety of environmental conditions. Traditional closed path sampling systems include a rain cap to prevent water ingress, an in-line filter to keep the analyzer windows clean, and tubing. Each component can influence the overall system frequency response, accuracy, maintenance requirements, and reliability. This work evaluates the performance of a new sample system design. This design replaces the inline-filter with a novel vortex air cleaner (U.S. Pat. No. 9,217,692), greatly reducing required maintenance, and increasing reliability. The system has excellent frequency response for both carbon dioxide and water vapor. Sample air temperature fluctuations are very effectively damped and the sample air temperature is well equilibrated with the cell block providing accuracy without the need for fine-wire thermocouples in the sample air path.