EasyFlux DL Eddy-Covariance Datalogger Program

Provides fully corrected outputs of CO2 flux, latent heat flux, and sensible heat flux at a user-defined interval (e.g., 30 minutes). Also provides many other variables of atmospheric properties, instrument diagnostics, intermediate corrections, and other energy balance or biomet sensors. Comparisons of flux outputs have shown good agreement with other common post-processing software packages when applying the same set of corrections. 

Benefits and Features 

• • Accesses final fluxes quickly without the burden of post-processing 
  • Produces flux output tables that are smaller than time series tables, which allows flux data to be frequently collected using cellular, radio, or other lower-bandwidth telemetry options 
  • Available at no charge; see Downloads section on web page 
  • Matches the fluxes provided by PC post-processing software packages (assuming same filtering of raw data and same selection of correction procedures) 
  • Saves high frequency time series to removable media in case reprocessing is later needed 
  • Includes data quality and footprint characteristics 
  • Reports uncorrected and intermediate values in an auxiliary output table for more detailed data inspection Provides for CR6 program fully processed data output in AmeriFlux format 

Main correction and processing procedures: 

• • Despike and filter high frequency time series data using sonic anemometer and gas analyzer diagnostic codes, signal strengths, and measurement output range thresholds. 
  • Apply coordinate rotations with an option to use the double rotation method (Tanner and Thurtell, 1969) or planar fit method (Wilczak et al., 2001). 
  • Lag CO2 and H2O measurements against sonic wind measurements for maximization of CO2 and H2O fluxes (Horst and Lenschow, 2009; Foken et al., 2012), with additional constraints to ensure lags are physically possible. 
  • Apply frequency corrections using commonly used cospectra (Moore, 1986; van Dijk, 2002; Moncrieff et al., 1997) and transfer functions for block averaging (Kaimal et al., 1989), line/volume averaging (Moore, 1986; Moncrieff et al., 1997; Foken et al., 2012; van Dijk, 2002), low-pass filter (Ibrom et al. 2007; FOR CPEC ONLY), time constants (Montgomery, 1947; Shapland et al., 2014; Geankoplis, 1993, Burgon et al. 2016), and sensor separation (Horst and Lenschow, 2009; Foken et al., 2012). 
  • Apply a modified SND correction (Schotanus et al., 1983) to derive sensible heat flux from sonic sensible heat flux following the implementation as outlined in van Dijk (2002). Additionally, fully corrected sensible heat flux computed from a fine-wire thermocouple is provided if our FW05, FW1, or FW3 is used. 
  • Apply correction for air density fluctuations using Webb et al., 1980. 
  • Assign data quality classifications (QC) based on steady state conditions and surface layer turbulence characteristics following Foken et al., 2002 to conform to AmeriFlux format. In addition, Foken et al., (2012) is also followed to include wind direction. An additional set of QC is provided. 
  • Calculate footprint characteristics using Kljun et al., 2004 or Kormann and Meixner, 2001. 
  • If energy balance sensors are used, calculate energy closure based on energy balance measurements and corrected sensible and latent heat fluxes. 
  • Sonic shadow correction is optional. 
  • CO2 spectroscopic correction using air temperature at high frequency nature as default and at convention as an option. CO2 values corrected using different air temperature are all stored at the measured frequency.