2.2 Eddy Covariance Tower Instrument Details
The eddy flux tower shown in Figure 1 stands at six meters high and supports multiple sensors. The sensor suite for the eddy covariance (EC)/energy balance system are provided in Table 1 and include air temperature and humidity sensors, a snow depth sensor, an air pressure transducer, a three-dimensional sonic anemometer with integrated CO2 and H2O open-path gas analyzer, two levels of soil moisture, soil temperature and soil electrical conductivity (5 cm and 25 cm), and ground heat flux plates located at a 5cm depth. The measurement height for the eddy covariance/infra-red gas analyzer and 4-way radiometer was set at just below 6 m (5.9 m) which is approximately 3-4 meters above the willow shrub gallery that covers much of the valley floor. The data recorded by these sensors are then processed using the EasyFlux-DL software following AmeriFlux guidelines (Aubinet, Vesala, & Papale, 2012, see Table 2 for description of EC processing options). Final data is output in 30-minute time increments. Data was then checked for reasonableness and missing time stamps are added, but no data was averaged to fill in the missing time gaps. This allows for the closest representation of tower measurements at the site. In this study, we have analyzed the data from April 15, 2017 to September 27, 2019. Energy balance closure was also assessed as a means of filtering out periods of incorrect or otherwise unreliable data. Details on closure analysis are provided below in Sections 2.3 and 3.1.