SGP/EBBR/E20 - Temperature/RH Probes Malfunction and Replacement

Beginning on approximately October 1, 1996 the calibration of the temperature 
sensor in one or both T/RH probes began to drift; temperatures started to 
drift higher than the thermocouple probes.  This drift caused the upper and 
lower temperatures measured by the T/RH probe to be 2 to 10 degrees C greater 
than the thermocouple probes.  Comparison with adjacent EBBR sites shows 
that the thermocouples were measuring properly.  The problem affected the vapor 
pressure outputs primarily, making them as much as 1 kPa greater than they 
should be (vapor pressure is calculated from probe temperature and relative 
humidity).  The effect on sensible and latent heat fluxes was negligible, 
although latent heat flux may be overestimated by about 5% presently and 
sensible heat flux underestimated by approximately the same percentage.


Site operations replaced the T/RH probes on 8 May 1996; the new probes are 
performing well. The serial numbers of replaced probes are: Left 632415, 
Right 632356.  New probe serial numbers are: Left 460428, Right 460412.

• Bottom T/RH sensor temperature(temp_trh_bottom)
• Bottom vapor pressure(vapor_pressure_bottom)
• Surface sensible heat flux(sensible_heat_flux)
• Bowen ratio(bowen_ratio)
• Top vapor pressure(vapor_pressure_top)
• Surface latent heat flux(latent_heat_flux)
• Top T/RH sensor temperature(temp_trh_top)

• Right T/RH sensor temperature (resistance ratio)(temp_trh_right_rr)
• Left T/RH sensor temperature (resistance ratio)(temp_trh_left_rr)

• (Raw data stream - documentation not supported)

• Top T/RH sensor temperature(temp_trh_top)
• Bottom vapor pressure(vapor_pressure_bottom)
• Bottom T/RH sensor temperature(temp_trh_bottom)
• Top vapor pressure(vapor_pressure_top)