Eddy Flux Measurements, Tussock Station, Imnavait Creek, Alaska - 2014


The Biocomplexity Station was established in 2005 to measure landscape-level carbon, water and energy balances at Imnavait Creek, Alaska. The station is now contributing valuable data to the Arctic Observing Network project that was established at two nearby stations. These will form part of a network of observatories with Abisko (Sweden), Zackenburg (Greenland) and a location in the Canadian High Arctic which will provide further data points as part of the International Polar Year. This particular part of the project focuses on simultaneous measurements of carbon, water and energy fluxes of the terrestrial landscape at hourly, daily, seasonal and multi-year time scales. These are the major regulatory drivers of the Arctic climate system and form key linkages and feedbacks between the land surface, the atmosphere and the oceans. We will provide a comprehensive description of the state of the regional Arctic system with respect to these variables, its overall regulation and controlling features and its interaction with the global system.

Project Keywords: 

Data set ID: 


EML revision ID: 

Published on EDI/LTER Data Portal


Bret-harte, M., Euskirchen, E., Griffin, K., Shaver, G. 2014. Eddy Flux Measurements, Tussock Station, Imnavait Creek, Alaska - 2014 Environmental Data Initiative. http://dx.doi.org/10.6073/pasta/65c267593c2cc3f16653c4536b9d956f

Date Range: 

Wednesday, January 1, 2014 to Thursday, December 31, 2015

Publication Date: 



There are two types of data that are collected from each flux station involved in the AON project: high frequency eddy covariance (EC) data and low frequency means of meteorological and subsurface data.  On a daily basis, approximately 75Mb of high frequency binary data and 16Kb of low frequency ASCII data is collected.

This station uses a CR3000 datalogger and a laptop to collect and store data.  The CR3000 is used to measure the open-path EC equipment which is sampled at 10Hz.  Mircrometeorlogical data is scanned at 0.33Hz and all datapoints are averaged every half hour.  The CRBASIC program that controls the datalogger has been written in such a way that only the most basic corrections and filtering are applied to the raw data.  These would include shifting the CSAT3 and LI7500 data arrays by 2 and 3 scans respectively to account for the inherent processing delays of these sensors. 

About Data Processing

Time is expessed as local time, AST (UTC-9hrs) for Imnavait and MAGST (UTC+12hrs) for Pleistocene Park

Gas and energy fluxes are calculated from the high frequency time series using EdiRe or EddyPro software with these basic corrections:  despiking, coordinate rotation, spectral correction, the 'WPL' correction, and the 'Burba' correction (where appropriate, to account for instrument heating effects).

Some data have been filtered (_f) and gap-filled (_gf).

The generation of mass and energy fluxes from the high frequency data is performed with the following basic corrections:

The 'WPL' correction

A coordinate rotation

A spectral correction

The 'Burba' correction (where appropriate to account for instrument heating effect)

*Correct instrument lag adjustment occurs during datalogging

The following QA/QC variables are applied to the flux data:

Stationarity tests

Footprint analysis

Gas analyzer diagnostics are used as a QA/QC variable for both flux and radiation data

Rejection angles of 10° at Imnavait and 45° at Pleistocene Park are used when EC instruments were downwind of tower to remove flow distortions 

The flux and meteorological data is further post-processed to accomplish the following:

Data are within engineering specifications of each instrument. 

Removal of impossible measurements (e.g. negative precipitation)

Removal of outliers via a three-standard deviation filter

Removal of unrealistic changes in a time series with a step change filter

A similarity filter to remove errors from instruments that generate a string of identical values when not working

Flux variables are calculated using Licor's EddyPro flux processing software. The quality control flags for flux variables (either raw or filtered) are calculated using the Mauder and Foken (2004) method within the EddyPro. Flag values and meanings are available on the Licor web site at https://www.licor.com/env/help/eddypro/topics_eddypro/Flux_Quality_Flags...

Gaps in the data are filled using the BGC_Jena gapfilling tool ReddyProc.  Information on the gap-filling protocol is available here, https://www.bgc-jena.mpg.de/bgi/index.php/Services/REddyProcWebGapFilling. The meaning of the quality control flags for all gap-filled (_gf) variables is listed here (https://www.bgc-jena.mpg.de/bgi/index.php/Services/REddyProcWebOutput) under the _fqc entry.

See the file  2014_IC_1993_metadata_20141231.csv for data collection statistics.

Imnavait Creek, Alaska

Fen Station - Sensor Suite

Instrument Model S/N Height (m) History Variables
CSAT3 CSAT3 Three Dimensional Sonic Anemometer 1418 2.18m Installed Aug., 2007 u',v',w'
LI-7500A LI-7500A Open Path Infrared Gas Analyzer (CO2 and H2O 2213 2.18m Installed June 2012, factory calibrated CO2, H2O, PA
LI-7700 LI-7700 Open Path Methane Analyzer (CH4) TG1-0217 2.18m Installed June 2012, factory calibrated CH4D, Temp, Press,
HMP45C HMP45C Temperature and Relative Humidity Probe C1440011 2m Installed Aug., 2007, Calibrated Apr.5, 2007 Ta_1, VP_1
NRLite NRLite Net Radiometer 72458 2m Installed Aug., 2007, Calibrated Jan.12, 2007, v RNET
HFP01SC HFP01SC Soil Heat Flux Plate : 001113 0.08m Installed Aug., 2007, Calibrated Mar.22, 2007 G1
HFP02SC HFP01SC Soil Heat Flux Plate : 001120 0.08m Installed Aug., 2007, Calibrated Mar.22, 2007 G2
HFP03SC HFP01SC Soil Heat Flux Plate : 001145 0.08m Installed Aug., 2007, Calibrated Apr.27, 2007 G3
HFP04SC HFP01SC Soil Heat Flux Plate : 001126 0.08m Installed Aug., 2007, Calibrated Apr.27, 2007 G4
TCAV TCAV Type E Thermocouple Averaging Soil Temperature P : n/a 0.02 a Installed Aug., 2007 TSOIL1
TCAV TCAV Type E Thermocouple Averaging Soil Temperature P : n/a 0.02 a Installed Aug., 2007 TSOIL2
CS616 CS616 Water Content Reflectometer (volumetric soil mo : n/a 0.025m Installed Aug., 2007 SWC1
CS616 CS616 Water Content Reflectometer (volumetric soil mo : n/a 0.025m Installed Aug., 2007 SWC2
TE525 Rain Gage 42359-507 n/a Installed Aug., 2007, Calibrated May 9, 2007 PRECIP
LI190SB PAR Sensor (incoming) Q44104 2m Installed Dec, 2010, Calibrated Sept 15, 2010 PAR
LI190SB PAR Sensor (outgoing) Q39549 2m Installed ?, Calibrated Apr 2011 PARUP
014A Wind Speed Sensor G4866 1.5m Installed Aug., 2007, Calibrated June 6, 2007 WS_1
SR50A Sonic Ranging Sensor 1203 2.18m Installed Aug 2007, internal chemicals replaced SNOWD
CMA6 Pyranometer/Albedometer 070014UPPE 2m Installed Aug, 2007, Calibrated Aug 2, 2007, ver Rg, Rg_out
IRR-P InfraRed Radiometer Sensor N/A 1.5m Installed June, 2008 TSURF

Version Changes: 

Dec 2014: Preliminary data through Oct 2014.
Feb 2015: Complete dataset Jan-Dec 2014
Ver 4: Jan 2018: Add code to send data set to Arctic Data Center. BK
June 2019-Version 6: Updated metadata, removing abbreviations. Added detail to site descriptions. BK

Sites sampled.

Full Metadata and data files (either comma delimited (csv) or Excel) - Environmental Data Initiative repository.

Use of the data requires acceptance of the data use policy --> Arctic LTER Data Use Policy