¶ Carbon Dioxide Flux (CO2FLX) Measurement Systems
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¶ Instrument Description
The Carbon Dioxide Flux (CO2FLX) measurement system at SGP includes a suite of instruments that are principally aimed at measuring 30-minute average fluxes of carbon dioxide (CO2) and latent and sensible heats. These measurements are made using the eddy covariance technique, wherein fluxes are given by the mean product of the vertical wind component (from sonic anemometers) and component densities or temperatures. With the use of a tall tower, many of these fluxes are measured at 4-, 25- and 60-m heights. In addition to these fluxes, different instrument systems under the CO2FLX moniker measure meteorological, trace gas mixing ratio, surface radiation and soil temperature, water content and heat flux characteristics.
The entire CO2FLX system at SGP is a little complex, but we'll walk through it here. When submitting a single CO2FLX DQA, please monitor the following nine (9) datastreams on a weekly basis:
Soil
- co2flxsoil.b1
- Soil heat fluxes, temperature and volumetric water content at various depths
4-meter Height
- co2flx4m.b1
- Primary flux measurements at 4-m height
- co2flxgas4m.a1
- Trace gas concentration densities at 4-m height
- co2flxrad4m.b1
- Shortwave and longwave radiation components, 4-m height
- co2flxwind4m.a1
- 3D wind components and temperature at 4-m height that are used to calculate primary fluxes
25-meter Height
- co2flx25m.b1
- Primary flux measurements at 25-m height
- co2flxwind25m.a1
- 3D wind components and temperature at 25-m height that are used to calculate primary fluxes
60-meter Height
- co2flx60m.b1
- Primary flux measurements at 60-m height
- co2flxwind60m.a1
- 3D wind components and temperature at 60-m height that are used to calculate primary fluxes
When submitting DQPRs for any CO2FLX data, please use the central CO2FLX instrument class.
¶ Additional Information
For more information, please see the CO2FLX Instrument web page.
¶ Expected Operations
¶ Metrics
Acceptable co2flxsoil.b1 Metrics Table
In the metrics table below, the four primary measurements are outlined in red; all other measurements are diagnostic in nature. Those primary fields are:
- calibrated_soil_heat_flux_7cm[1-4] - soil heat flux at a depth of 7 cm, sensors 1 - 4
Acceptable co2flx4m.b1 Metrics Table
In the co2flx4m.b1 metrics table below, the five primary measurements are outlined in red; all other measurements are diagnostic in nature. Those primary fields are:
- co2_flux - Carbon dioxide flux at 4-m height
- h2o_flux - water vapor flux at 4-m height
- momentum_flux - momentum flux at 4-m height
- sensible_heat_flux - sensible heat flux at 4-m height
- latent_heat_flux - latent heat flux at 4-m height
Acceptable co2flxgas4m.a1 Metrics Table
In the metrics table below, the two primary measurements are outlined in red; all other measurements are diagnostic in nature. Those primary fields are:
- co2_concentration - carbon dioxide density, 4-m height
- h2o_concentration - water vapor density, 4-m height
Acceptable co2flxrad4m.b1 Metrics Table
In the metrics table below, all measurements can be considered primary in nature. They are:
- total_solar - total solar radiation, 4-m height
- downwelling[upwelling]_shortwave - downwelling and upwelling shortwave radiation, 4-m height
- downwelling_diffuse[direct]_shortwave - downwelling defuse and direct shortwave radiation, 4-m height
- downwelling[upwelling]_longwave - downwelling and upwelling longwave radiation, 4-m height
- downwelling[upwelling]_photosynthetic_active_radiation - downwelling and upwelling photosynthetic active radiation, 4-m height
Acceptable co2flxwind4m.a1 Metrics Table
In the metrics table below, all measurements can be considered primary in nature. They are:
- [u, v, w]_wind - Eastward, Northward and vertical wind speed components at 4-m height
- sonic_temperature - sonic temperature at 4-m height
Acceptable co2flx25m.b1 Metrics Table
In the metrics table below, the two primary measurements are outlined in red; all other measurements are diagnostic in nature. Those primary fields are:
- momentum_flux - momentum flux at 25-m height
- sensible_heat_flux - sensible heat flux at 25-m height
Acceptable co2flxwind25m.a1 Metrics Table
In the metrics table below, all measurements can be considered primary in nature. They are:
- [u, v, w]_wind - Eastward, Northward and vertical wind speed components at 25-m height
- sonic_temperature - sonic temperature at 25-m height
Acceptable co2flx60m.b1 Metrics Table
In the metrics table below, the two primary measurements are outlined in red; all other measurements are diagnostic in nature. Those primary fields are:
- momentum_flux - momentum flux at 60-m height
- sensible_heat_flux - sensible heat flux at 60-m height
Acceptable co2flxwind60m.a1 Metrics Table
In the metrics table below, all measurements can be considered primary in nature. They are:
- [u, v, w]_wind - Eastward, Northward and vertical wind speed components at 60-m height
- sonic_temperature - sonic temperature at 60-m height
¶ Plots
¶ co2flxsoil.b1 Plots
The co2flxsoil.b1 diagnostic plot suite includes daily time series of:
Soil heat flux at a depth of 7.5 cm, sensors 1-4
Note that calibration maneuvers have been screened from these time series, resulting in multiple operational short-duration "gaps" per day that do not need to be mentioned when reporting on DQ.
Soil volumetric water content and temperature at various depths
Note that calibration maneuvers have been screened from these time series, resulting in multiple operational short-duration "gaps" per day that do not need to be mentioned when reporting on DQ.
Surface meteorological measurements
¶ co2flx4m.b1 Plots
The co2flx4m.b1 diagnostic plot suite includes daily and weekly time series of:
Series of primary fluxes at 4-m height
Carbon dioxide and water vapor mixing ratios at 4m-height
Meteorological measurements at 4-m height
¶ co2flxgas4m.a1 Plots
The co2flxgas4m.a1 diagnostic plot suite includes daily and weekly time series of:
Carbon dioxide (left y-axis) and water vapor (right y-axis) concentration densities
Diagnostic temperature, pressure and signal strength
¶ co2flxrad4m.b1 Plots
The co2flxrad4m.b1 diagnostic plot suite includes daily and weekly time series of:
Components of shortwave, longwave and photosynthetically active radiation
Note that a cloud flag at the top of these plot panels should indicate the presence of clouds, both throughout the day and night. This could help debunk spikes and dips in these shortage and longwave radiation fields. Question for further thought - how would you expect the presence of clouds to influence shortwave and longwave radiation components?
¶ co2flxwind4m.a1 Plots
The co2flxwind4m.a1 diagnostic plot suite includes daily and weekly time series of:
3D wind components and sonic temperature at a height of 4m
¶ co2flx25m.b1 Plots
The co2flx25m.b1 diagnostic plot suite includes daily and weekly time series of:
Momentum and sensible heat flux at a height of 25 m
Sonic temperature, horizontal wind speed and direction and vertical wind speed at a height of 25 m
¶ co2flxwind25m.a1 Plots
The co2flxwind25m.a1 diagnostic plot suite includes daily and weekly time series of:
3D wind components and sonic temperature at a height of 25 m
¶ co2flx60m.b1 Plots
The co2flx60m.b1 diagnostic plot suite includes daily and weekly time series of:
Momentum and sensible heat flux at a height of 60 m
Sonic temperature, horizontal wind speed and direction and vertical wind speed at a height of 60 m
¶ co2flxwind60m.a1 Plots
The co2flxwind60m.a1 diagnostic plot suite includes daily and weekly time series of:
3D wind components and sonic temperature at a height of 60 m
¶ Site-Specific Information
The CO2FLX is located at SGP C1.
¶ Known Behaviors
¶ Known Issues
Known issues that may not need to be mentioned in DQAs are mentioned below:
Occasional Missing Data for co2flx4m, co2flx25m, or co2flx60m
Rainy periods associated with frontal system passages can lead to precipitation blocking the sensor path of the gas analyzer. This can cause data to be flagged or removed during data processing.
¶ Past Problems
Past Problems that DO need to be mentioned in DQAs are mentioned below:
Solar radiation sensor malfunction
Temperature/RH sensor failure
