DQRID : D970627.2
Start DateStart TimeEnd DateEnd Time Data Quality Metric
12/03/1996193006/17/19972030Incorrect
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Subject:
SGP/EBBR/E26 - Reprocess: E26 Soil Heat Flow Sensor 1 Replacement
DataStreams:sgp30ebbrE26.b1, sgp15ebbrE26.b1
Description:
Apparently, during installation of the present system on 17 July 1996, soil 
heat flow sensor #4 was intentionally placed upside down in the soil to 
produce the correct sign of flux. The leads from the sensor must have been
connected with the wrong polarity.  On 3 December 1996 site operations 
corrected some wiring problems and reconnected soil heat flow sensor #4 
according to the proper color code; this caused the sign of the soil heat 
flow from that sensor to then be opposite of the other four sensors.  All 
data from sensor #4 is the wrong sign during the period listed above.

On 17 June 1997 site operations removed the sensor and installed it with 
the correct side up, fixing the problem.

The result of this problem was a decrease of reported average soil heat flow of 
approximately 40%.  This translates into a 0 to 20% error in latent and 
sensible heat fluxes (soil heat flow is rarely more than 50% of net radiation,
upon which the Bowen ratio calculation depends).  Therefore, sensible and 
latent heat fluxes were typically overestimated by about 10% during the 
daytime.  This is of the same magnitude as the EBBR system/technique error.

The following data values were affected for the period listed 
above: 

15 minute: mv_hft4
30 minute: shf4, c_shf4, g4, ave_shf, e, h

The latent and sensible heat fluxes can be recalculated by using only soil
heat flows 1, 2, 3, and 5 to calculate the average soil heat flow,

ave_shf = (g1 + g2 + g3 + g5)/4

e = -(q + ave_shf)/(1 + bowen)

h = -(e + ave_shf + q).
Suggestions: 
Measurements:sgp15ebbrE26.b1:
  • soil_heat_flow_4_mv
more
sgp30ebbrE26.b1:
  • corr_soil_heat_flow_4
  • soil_heat_flow_4
  • sensible_heat_flux
  • latent_heat_flux
  • surface_soil_heat_flux_avg
  • surface_soil_heat_flux_4
more

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