SGP/CO2FLX/C1 - Reprocessing User Notes

Format Changes:
  To comply with archive standards, the name of the unlimited dimention variable in the 
cdf level b1 files was changed from 'record' to 'time'. This does not affect data quality.

• Mean horizontal wind speed(mean_rot_u)
• Mean air temperature (lower level)(t_air_lower)
• Mean CO2 density(mean_c)
• z_m_soil_upper
• base_time
• Average of two upper soil temperature sensors(mean_t_soil_upper)
• Wind speed, W-to-E component, at altitude, derived from ETA model(wdir)
• Average of two middle soil temperature sensors(mean_t_soil_middle)
• zm
• phi
• Pressure, atmospheric, surface, 1-min avg(bar_pres)
• Mean relative humidity (upper level)(rh_upper)
• stderr_mean_m_soil_lower
• Mean air temperature (upper level)(t_air_upper)
• z_upper
• Downwelling longwave hemispheric irradiance; t_rad corrected(r_down_long_hemisp)
• Downwelling shortwave hemispheric irradiance; t_rad corrected(r_down_short_hemisp)
• Average of four lower soil moisture sensors(mean_m_soil_lower)
• Total downwelling shortwave radiation (LI-200 sensor)(r_tot)
• Additive WPL H correction to c flux(fc_wpl_h)
• doy
• stderr_mean_g_soil
• mean_p
• Mean H2O density(mean_q)
• Mean sonic temp(mean_t)
• stderr_mean_t_soil_lower
• Average of four upper soil moisture sensors(mean_m_soil_upper)
• t_rad
• WPL corrected latent heat flux(le)
• z_m_soil_lower
• z_t_soil_middle
• site_elevation
• stderr_mean_t_soil_middle
• Average of two lower soil temperature sensors(mean_t_soil_lower)
• yyyydddhhmmss
• Net solar radiation (NR-lite); t_rad corrected(r_net)
• Monin-Obukhov length scale(Lmoni)
• site_latitude
• Upwelling longwave hemispheric irradiance; t_rad corrected(r_up_long_hemisp)
• Mean relative humidity (lower level)(rh_lower)
• z_t_soil_upper
• Variance of rotated w(var_rot_w)
• z_lower
• Variance of v(var_rot_v)
• zrad
• time_offset
• z_t_soil_lower
• Variance of rotated u(var_rot_u)
• Photosynthetic photon flux density (PAR)(ppfd)
• Upwelling shortwave hemispheric irradiance; t_rad corrected(r_up_short_hemisp)
• stderr_mean_m_soil_upper
• variance of variable t(var_t)
• Average of four soil heat flux probes(mean_g_soil)
• theta
• stderr_mean_t_soil_upper
• Additive WPL LE correction to fc(fc_wpl_le)
• Precipitation(precip)
• Variance of q(var_q)
• site_longitude
• WPL corrected CO2 flux(fc_corr)
• Variance of c(var_c)
• Corrected sensible heat flux(h)
• friction velocity(ustar)
• z_g_soil

SGP/CO2FLX/C1 - Reprocessing User Notes

A subset of the radiation measurements had an incorrect gain applied to raw data in period 
from 20021218-20031218.  To correct for this, a multiplicative correction factor of 1.11 
were applied to raw data used for the following variables:

r_down_short_hemisp
r_down_long_hemisp
r_up_short_hemisp
r_up_long_hemisp

Note that the long wave variables are computed by adding the black body thermal radiation 
from the radiometer body to each of the long wave signals.  Hence, the multiplicative 
correction is applied to the raw long wave fluxes before adding in the flux from the 
radiometer body.

• Downwelling shortwave hemispheric irradiance; t_rad corrected(r_down_short_hemisp)
• Upwelling longwave hemispheric irradiance; t_rad corrected(r_up_long_hemisp)
• Upwelling shortwave hemispheric irradiance; t_rad corrected(r_up_short_hemisp)
• Downwelling longwave hemispheric irradiance; t_rad corrected(r_down_long_hemisp)

SGP/CO2FLX/C1 - Longwave Radiation Incorrect

Long wave radiation values (r_up_long_hemisp, r_down_long_hemisp) are bad 
due to correction with bad radiometer body temperature (t_rad) resulting
from a wiring issue.

• t_rad
• Upwelling longwave hemispheric irradiance; t_rad corrected(r_up_long_hemisp)
• Downwelling longwave hemispheric irradiance; t_rad corrected(r_down_long_hemisp)

SGP/CO2FLX/C1 - Reprocessed: User Notes

Replacement of LI-200 sensor (total downwelling shortwave radiation, variable r_tot) by a 
new LI-190 sensor (upwelling photosynthetic photon flux density, variable ppfd_up).

The new LI-190 sensor was:
- installed on December 9, 2004. 
- being tested from December 9, 2004 to December 22, 2004.
- operational after December 22, 2004.

Consequently:
1. variable "r_tot" is filled with missing values (qc_r_tot = 1) after December 9, 2004,
2. variable "ppfd_up" is filled with missing values (qc_ppfd_up = 1) prior December 22, 
2004.

• ppfd_up
• Total downwelling shortwave radiation (LI-200 sensor)(r_tot)

SGP/CO2FLX/C1 - downwelling longwave hemispheric irradiance incorrect

A problem was identified with the downwelling longwave hemispheric irradiance (variable 
"r_down_long_hemisp") calibration of our Kipp & Zonen CNR1 radiometer. The offset of the 
instrument is believed to be incorrect over the specified time frame, and a correction of 
the problem is underway.

• Downwelling longwave hemispheric irradiance; t_rad corrected(r_down_long_hemisp)

SGP/CO2FLX/C1 - Soil Temperature measurements

Current data quality check (qc) procedure does not catch spikes in soil temperature 
measurements. A new qc procedure is being tested and will improve the current procedure.

• Average of two upper soil temperature sensors(mean_t_soil_upper)
• Average of two middle soil temperature sensors(mean_t_soil_middle)
• Average of two lower soil temperature sensors(mean_t_soil_lower)

SGP/CO2FLX/C1 - Met stand was moved

Ameriflux program (Hank Loescher from Oregon state university) visits the site to 
intercompare his instruments with our 4m flux system.
The met stand was moved by 30 feet and consequently:
1. Soil moisture sensors were disconnected,
2. Soil temperature sensors were disconnected,
3. Soil heat plates were disconnected,
4. The true direction of the anemometer boom was 230 degrees instead of the regular 270 
degrees.

• Average of four upper soil moisture sensors(mean_m_soil_upper)
• Average of four lower soil moisture sensors(mean_m_soil_lower)
• Wind speed, W-to-E component, at altitude, derived from ETA model(wdir)
• Average of two upper soil temperature sensors(mean_t_soil_upper)
• Average of two middle soil temperature sensors(mean_t_soil_middle)
• Average of two lower soil temperature sensors(mean_t_soil_lower)
• Average of four soil heat flux probes(mean_g_soil)

SGP/CO2FLX/C1 - downwelling longwave hemispheric irradiance incorrect

Downwelling longwave radiation measurements (variable "r_down_long_hemisp") are bad due to 
a wiring issue. Users should not use the downwelling longwave hemispheric irradiance 
during this period. The downwelling shortwave and longwave radiation at CF is also available 
from the Broadband Radiometer Station (BRS).

• Downwelling longwave hemispheric irradiance; t_rad corrected(r_down_long_hemisp)

SGP/CO2FLX/C1 - Disturbance around site

A bulldozer used to excavate the SGP Tower anchors was right around (within 10 feet) our 
systems.

• WPL corrected CO2 flux(fc_corr)
• Mean CO2 density(mean_c)

SGP/CO2FLX/C1 - Farm operation

Soil temperature, soil moisture, soil heat flux and upwelling surface radiation (long, 
short, and PAR) measurements were not valid from 20070822 to 20070907 due to farm operations.

• stderr_mean_t_soil_lower
• Average of four upper soil moisture sensors(mean_m_soil_upper)
• stderr_mean_m_soil_lower
• Upwelling shortwave hemispheric irradiance; t_rad corrected(r_up_short_hemisp)
• stderr_mean_m_soil_upper
• stderr_mean_t_soil_middle
• Average of two lower soil temperature sensors(mean_t_soil_lower)
• Average of four soil heat flux probes(mean_g_soil)
• stderr_mean_t_soil_upper
• ppfd_up
• Average of four lower soil moisture sensors(mean_m_soil_lower)
• Upwelling longwave hemispheric irradiance; t_rad corrected(r_up_long_hemisp)
• Average of two upper soil temperature sensors(mean_t_soil_upper)
• stderr_mean_g_soil
• Average of two middle soil temperature sensors(mean_t_soil_middle)