SGP/EBBR/E26 - Wind Direction Sensor Malfunction

The wind direction sensor malfunctioned, outputting nearly a 
constant value, invalidating the following data values.

30 minute: wind_d, sigma_wd, res_ws

15 minute: mv_wind_d

5 minute: wind_d, sigma_wd, res_ws

The first good data after the affected period was the 1700 GMT, 30 minute
data on March 16, 1994.

• Wind direction (relative to true north)(mv_wind_d)

• wind direction (relative to true north)(wind_d)
• vector wind speed(res_ws)
• standard deviation of wind direction (sigma theta)(sigma_wd)

• vector wind speed(res_ws)
• wind direction (relative to true north)(wind_d)
• standard deviation of wind direction (sigma theta)(sigma_wd)

SGP/EBBR/E22 - Reprocess: Soil Heat Flow Sensor 4 Incorrect Data

Soil heat flow sensor #4 periodically output incorrect values during the 
period indicated.  The output often indicated large negative heat flow.  The
sensor was replaced on March 19, 1996, which corrected the problem.  The data 
affected (and thus incorrect) includes:

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

The dates and times (GMT) of incorrect values are listed below.  Only half 
hour data times are listed.  

01/31/96  1500 (shf4 only)
02/10/96  0230-1300, 1400-1600
02/11/96  0100-0900, 1030-1400, 1730-2330
02/12/96  0000-0100, 1200-1230, 1600-1830
02/13/96  0130-0230, 1430, 1600-1700
02/14/96  0130-0230
02/23/96  0330-0530, 1200-2330
02/24/96  0000-0200
02/29/96  0000
03/03/96  0130-0200, 1500-1830
03/04/96  0100-0230, 0400-1530
03/05/96  1200-1430, 1630-1830
03/06/96  0200-2330
03/07/96  0000-0430, 2030-2130, 2330
03/08/96  0330-1730
03/10/96  0400-1130
03/12/96  0400-1130, 1430-1600
03/13/96  0830-1130
03/15/96  0400-2200
03/16/96  0400-0830, 1030-1200, 1500-1700
03/17/96  0630, 0730-2030
03/18/96  0300-1730
03/19/96  0130-2330
03/20/96  0000-1430, 1700-1830
03/21/96  0230
03/22/96  0400, 1600-1700
03/23/96  0400-1930
03/24/96  2200-2330
03/25/96  0000-1500
03/27/96  1800-2000

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)

• 5 cm soil heat flow corrected for soil moisture content, site 4(c_shf4)
• h(h)
• latent heat flux(e)
• soil heat flow, site 4(g4)
• 5 cm soil heat flow, site 4(shf4)
• average surface soil heat flow(ave_shf)

• Soil heat flow 4(mv_hft4)

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.

• null(Raw data stream - documentation not supported)

• ratio of sensible/latent heat fluxes (Bowen ratio)(bowen)
• Temperature of the top humidity chamber(thum_top)
• Temperature of bottom humidity sensor chamber(thum_bot)
• bottom vapor pressure(vp_bot)
• latent heat flux(e)
• top vapor pressure(vp_top)
• h(h)

• Temperature of the top humidity chamber(thum_top)
• bottom vapor pressure(vp_bot)
• Temperature of bottom humidity sensor chamber(thum_bot)
• top vapor pressure(vp_top)

• Temperature of right humidity sensor chamber(rr_thum_r)
• Temperature of left humidity sensor chamber(rr_thum_l)

SGP/EBBR/E26 - Reprocess: E26 Soil Heat Flow Sensor 1 Replacement

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).

• Soil heat flow 4(mv_hft4)

• soil heat flow, site 4(g4)
• 5 cm soil heat flow corrected for soil moisture content, site 4(c_shf4)
• average surface soil heat flow(ave_shf)
• h(h)
• latent heat flux(e)
• 5 cm soil heat flow, site 4(shf4)

SGP/EBBR/E22 - Reprocess: E22 Soil Heat Flow Sensor # 5 Incorrect Data

Soil heat flow sensor #5 frequently produced large negative (and incorrect)
values during the period above.  The problem ended during a PM visit by 
site operations.  However, there is no documentation by Site Operations in
the instrumentation report or corrective maintenance report that Site
Operations personnel took action to correct the problem.  Site Operations 
also told me that they have no record of any changes or corrective 
maintenance.  Apparently, something fortuitous happened during the PM to 
correct the problem.  The start date and time of the problem cannot be 
determined exactly, but it did begin during a period of missing data from 
Feb. 14-25, 1997.

Values affected (and thus incorrect) include:

15 minute: mv_hft5
30 minute: shf5, c_shf5, g5, ave_shf, e, h.

The latent and sensible heat fluxes can be recalculated by using only soil
heat flows 1, 2, 3, and 4 to calculate the average soil heat flow,

ave_shf = (g1 + g2 + g3 + g4)/4

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

h = -(e + ave_shf + q)

• h(h)
• latent heat flux(e)
• 5 cm soil heat flow, site 5(shf5)
• average surface soil heat flow(ave_shf)
• 5 cm soil heat flow corrected for soil moisture content, site 5(c_shf5)

• Soil heat flow 5(mv_hft5)

SGP/EBBR/E25 - Bowen Ratio Usually Negative - Fluxes Incorrect

Submitted By:                         _x_  Instrument Mentor
                                      ___  EST Member
                                      ___  Science Team Member
                                      ___  Other

Platform/Measurement: EBBR/Bowen ratio, sensible and latent heat fluxes
	What level data: (raw,a0,a1,b1,c1 etc): a1 (15 and 30 minute)

  What location was the data collected at: E25, Seminole, OK

  Period of time in question (Times vary for different days)

 	Begin Date 10/22/97  and on

Discussion of Problem:

Bowen ratio is normally negative, as if it is somehow being biased.
Latent and sensible heat fluxes are apparently incorrect much of the
time, especially during the daytime.  All supporting measurements seem
to be incorrect; therefore the error must be occurring in the measured
T and RH gradients.  This situation has occured since the EBBR unit was
installed on 22 October 1997.  A work request has been submitted for a
full six month check to be performed on the system.  Hopefully the checks
will point to the source of the problem.

The right relative humidity was biased.  The right T/RH probe was
replaced on 4/22/98 at 1700 GMT, but it had a more defective RH sensor
in it, causing right RH to sit at 112-114 percent.  This probe was
itself replaced on 5/6/98 at 1645 GMT, thereby taking care of the negative
Bowen ratio problem.

• Right relative humidity(mv_hum_r)

• Bottom humidity(hum_bot)
• bottom vapor pressure(vp_bot)
• top vapor pressure(vp_top)
• Top humidity(hum_top)

• top vapor pressure(vp_top)
• bottom vapor pressure(vp_bot)
• latent heat flux(e)
• ratio of sensible/latent heat fluxes (Bowen ratio)(bowen)
• h(h)
• Bottom humidity(hum_bot)
• Top humidity(hum_top)