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University of Colorado, UCB 260
Boulder, CO 80303
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Two identical 3-meter towers were installed near T-Van in 2007, and continuous meteorological and eddy covariance data are presented beginning in 2008. The sampling interval was 5 seconds for the meteorological data and 10 Hz for the eddy covariance data, and 30-minute means of all variables were calculated using a Campbell Scientific CR3000 datalogger. The 30-minute mean data were subsequently averaged to create this 24-hour mean dataset. Information about specific sensors, instrumental orientation, units, and data post-processing and infilling procedures are contained in the metadata for this file.
Eddy covariance towers were located near Tvan in alpine tundra fellfield/dry meadow vegetation. The east tower (3502 m asl) was situated 50 horizontal meters northwest of T-Van (source of 120-V AC power), and the west tower (3504 m asl) was 50 horizontal meters west of the east tower along the prevailing wind direction and a 7.8% snow-scoured slope.
Latitude: 40 degrees 03 minutes 11 seconds north
Longitude: 105 degrees 35 minutes 11 seconds west
2008-1-1 to ongoing
air temperature, relative humidity, air pressure, wind speed, wind direction, net radiation, soil temperature, volumetric water content, latent heat flux, sensible heat flux, soil heat flux, net ecosystem exchange
T-Van, photo credit: John Knowles
Niwot Ridge (USFS - UNESCO Biosphere Reserve)
Located in: USFS - UNESCO Biosphere Reserve
(Click to learn more about these locations)
More data from: Tvan
Core Data Set: No
Discipline: Climatology/meteorology, Biogeochemistry
Award Or Grant: DEB1637686
Abbreviations and Units:
LE: Latent heat flux (W m-2)
H: Sensible heat flux (W m-2)
G: Soil heat flux (W m-2)
Rn: Net radiation (W m-2)
Ta: Air temperature (oC)
Rh: Relative humidity (%)
U: Wind speed (m s-1)
WD: Wind direction (degrees)
Pa: Air pressure (kPa)
NEE: Net ecosystem exchange of carbon dioxide (µmol m-2 s-1)
VWC: Volumetric soil moisture (%)
Ts: Soil temperature (oC).
Temperature/Humidity probe (Ta, Rh): Vaisala, HMP45C, oriented to 360 degrees, 3 m above ground level.
Net Radiometer (Rn): Kipp and Zonen, NR-LITE, oriented to 180 degrees, 3 m above ground level.
Sonic Anemometer (U, WD, LE, H, NEE): Campbell Scientific, CSAT3, oriented to 360 degrees, 3 m above ground level.
Infrared Gas Analyzer (Pa, LE, NEE): Li-Cor, LI-7500, oriented to 360 degrees, mounted 10 horizontal cm from the CSAT3, 3 m above ground level.
Soil Heat Flux (G): Average of 2 plates (REBS HFT 3) buried to 2 cm depth beneath the ground, one beneath a vegetated surface, one beneath bare rock.
Soil Moisture (VWC): Sentek EnviroSmart capacitance probe with sensor at 20 cm depth.
Soil Temperature (Ts): 2 pairs of Campbell Scientific TCAV-L Type E thermocouples, buried at a distance of 20 horizontal cm from each other, 10 vertical cm beneath the soil surface.
Daily data were averaged from 30-minute means of data sampled at 10 Hz (LE, H, and NEE), 5 seconds (all other meteorology), or 5 minutes (VWC and Ts).
Rh was determined as the ratio of the vapor pressure (ea) as converted from vapor density (rho_v) by ea (kPa) = rho_v (g m-3)*8.3143*Ta (K)/18.02/1000 to the saturation vapor pressure (kPa).
Eddy covariance data (LE, H, NEE) were subject to two-dimensional coordinate rotation and Webb adjustment following Lee et al. (2004) Handbook of Micrometeorology: A Guide for Surface Flux Measurements and Analysis, Kluwer Academic Publishers, Dordrecht, Netherlands.
Data Infilling Procedures:
LE: Linear regression of Rn vs LE for Mar-Oct and multiple regression of Rn, U, Ta, and Rh vs LE for Nov-Feb
H: Linear regression of Rn vs H for Mar-Oct and multiple regression of Rn, U, Ta, and Rh vs H for Nov-Feb
G, Ts: Mean value for the given timestep during the preceding and succeeding seven day periods
NEE, Ta, Rh, U, Rn, Pa: Missing values replaced by the average value under similar meteorological conditions following Falge et al. (2001) Agricultural and Forest Meteorology, Reichstein et al. (2005) Global Change Biology, and Markus Reichstein and Antje Maria Moffat (2014), REddyProc: Data processing and plotting utilities of (half-)hourly eddy-covariance measurements. R package version 0.6-0/r9
WD, VWC: Cubic interpolation between missing values.
eddy covariance, energy, net ecosystem exchange, NEE, heat flux, air temperature, relative humidity, soil temperature, wind speed, wind direction, volumetric water content, water, carbon, climate, Tvan towers, data logger, sensor, cr3000, Niwot Ridge LTER, NWT, gap filled, infilled, long term
COL1. label=date, type=string, units=none, missing value indicator=NaN, minimum=2008-01-01, maximum=, precision=, definition=date (yyyy-mm-dd)
COL2. label=year, type=integer, units=none, missing value indicator=NaN, minimum=2008, maximum=, precision=1
COL3. label=jday, type=integer, units=none, missing value indicator=NaN, minimum=1, maximum=366, precision=1, definition=Julian day
COL4. label=airtemp_avg, type=real, units=celsius, missing value indicator=NaN, minimum=, maximum=, precision=, definition=average air temperature
COL5. label=rh_avg, type=real, units=percent, missing value indicator=NaN, minimum=, maximum=, precision=, definition=average relative humidity
COL6. label=air_press, type=real, units=kilopascal, missing value indicator=NaN, minimum=, maximum=, precision=, definition=air pressure
COL7. label=ws_avg, type=real, units=meterPerSecond, missing value indicator=NaN, minimum=, maximum=, precision=, definition=average wind speed
COL8. label=wd_avg, type=real, units=degree, missing value indicator=NaN, minimum=0, maximum=360 precision=, definition=average wind direction
COL9. label=netrad, type=real, units=wattPerMeterSquared, missing value indicator=NaN, minimum=, maximum=, precision=, definition=net solar radiation
COL10. label=soiltemp_10cm, type=real, units=celsius, missing value indicator=NaN, minimum=, maximum=,
precision=, definition=soil temperature at 10 cm depth
COL11. label=vwc_10cm, type=real, units=percent, missing value indicator=NaN, minimum=, maximum=,
precision=, definition=soil volumetric water content at 20 cm depth
COL12. label=heatflux_lat, type=real, units=wattPerMeterSquared, missing value indicator=NaN, minimum=, maximum=,
precision=, definition=latent heat flux
COL13. label=heatflux_sens, type=real, units=wattPerMeterSquared, missing value indicator=NaN, minimum=, maximum=,
precision=, definition=sensible heat flux
COL14. label=heatflux_soil, type=real, units=wattPerMeterSquared, missing value indicator=NaN, minimum=, maximum=,
precision=, definition=soil heat flux
COL15. label=NEE, type=real, units=micromolePerMeterSquaredPerSecond, missing value indicator=NaN, minimum=, maximum=,
precision=, definition=net ecosystem exchange of carbon dioxide
*Note: To ask a question about data content, please contact the data manager HERE
To ask a question about methodology, please contact Peter Blanken,
 PD Blanken et al. 2009. A comparison of water and carbon dioxide exchange at a windy alpine tundra and subalpine forest site near Niwot Ridge, Colorado. Biogeochemistry, Vol. 95, pages 61-76.
 JF Knowles et al. 2012. Energy and surface moisture seasonally limit evaporation and sublimation from snow-free alpine tundra. Agricultural and Forest Meteorology, Vol. 157, pages 106-115.
 JF Knowles et al. 2014. Fluxes of energy, water, and carbon dioxide from mountain ecosystems at Niwot Ridge, Colorado. Plant Ecology & Diversity.
This metadata file and data set were developed from information and data provided by John Knowles.[HCH 16 January 2016] Temperature units changed to celsius.[HCH 27 April 2017]
Knowles, John. Blanken, Peter. 2018. Infilled climate and heat flux data for Tvan towers data loggers (CR3000) from 2008-1-1 to ongoing, daily. http://niwot.colorado.edu
This material is based upon work supported by the National Science Foundation under Cooperative Agreement #DEB-1637686. Any opinions, findings, conclusions, or recommendations expressed in the material are those of the author(s) and do not necesarily reflect the views of the National Science Foundation.
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