SGP/EBBR/E19 - Metadata errors

The latitude, longitude and altitude of the El Reno (E19) site were
incorrectly entered into the ARM database.  The correct location
of the EBBR.E19 instrument is:
 Lat: 35.557N
 Lon: 98.017W
 Alt:    421m

• alt
• lon
• lat

• alt
• lon
• lat

• lon
• lat
• alt

SGP/EBBR/E19 - Wind Direction Dependency of Surface Fluxes and General Data Quality 
Information

Beginning in FY2006, Data Quality Reports are not written for missing 
data or for situations when qc flags clearly show that the data is 
incorrect (this is true for most of the conditions listed below).  
DQRs are written for periods when data is incorrect, when the situation 
is not represented by qc flags in the data, and it's not obvious that 
the data should have been flagged as incorrect.

The EBBR data is only useful for particular wind directions at each 
Extended Facility.  Please use the following resources to help in 
interpreting the EBBR data.

1) qc flags in the EBBR data.

2) Instrument Mentor Monthly Summaries (IMMS) at http://www.db.arm.gov/IMMS/

3) SGP EF Surface Conditions Observations (EFSCO) at 
http://198.124.96.210:591/sfc_cond1/default.htm

4) Surface fluxes are valid only for the following wind directions
(in degrees):

0-133, 151-360

Note that there are wind directions at most sites for which the fetch
is insufficient and therefore EBBR data is invalid.  Appropriate 
fetch was determined from a 1/40 measurement height to fetch ratio, 
resulting in a required minimum fetch of 120 m.  Particular attention 
should be paid to the limited valid wind directions for the Central 
Facility EBBR.  The surface vegetation type for the EBBRs is grazed 
or ungrazed grassland (refer to the EFSCO for state).

5) Some conditions that commonly cause the EBBR primary measurements to 
be incorrect or missing follow:

a) Sensible and latent heat fluxes are not accurate during times when 
the Automatic Exchange Mechanism (AEM) is not functioning properly.  
The AEM switches the gradient measuring instrumentation between the 
top and bottom positions every 15 minutes; this reduces the effects of 
instrument offsets.  Sometimes the AEM does not reach it's full extent 
of travel, resulting in the home signal being zero.  

b) Sensible and latent heat fluxes are sometimes incorrect when surface 
soil heat flow is out of range, as seen in the average soil heat flux 
(ave_shf).

c) Very light winds may be seen at nights for brief periods. Wind 
direction flops around a lot during low wind conditions (< 1.5 m/s) 
and is often unreliable during those periods.

d) Missing data periods occur at times; this is usually a site data 
system collection/communication problem; it can also occur during 
replacement of the system with a newly calibrated unit.  Missing data 
is sometimes filled in later from manual or automatic re-collection of 
the data.

• energy_storage_change_3
• energy_storage_change_2
• energy_storage_change_5
• energy_storage_change_4
• home_signal_15
• vapor_pressure_top
• energy_storage_change_1
• Wind direction, vector, lower, 1-min avg(wdir_vec_mean)
• temp_trh_bottom
• soil_temp_5
• Radiation, net(net_radiation)
• soil_temp_1
• soil_temp_2
• soil_temp_3
• lat
• soil_temp_4
• surface_soil_heat_flux_1
• soil_moisture_2
• surface_soil_heat_flux_2
• soil_moisture_1
• soil_moisture_4
• soil_heat_capacity_4
• soil_heat_capacity_5
• soil_moisture_3
• surface_soil_heat_flux_5
• soil_heat_capacity_2
• soil_heat_capacity_3
• surface_soil_heat_flux_3
• wdir_vec_std
• soil_heat_capacity_1
• surface_soil_heat_flux_4
• rh_bottom_fraction
• Average soil heat flow at the surface(surface_soil_heat_flux_avg)
• Wind speed, lower, 1-min avg(wspd_arith_mean)
• Wind speed vector mean(wspd_vec_mean)
• bowen_ratio
• soil_moisture_5
• Heat flux, sensible, at 1.5-m height, 30-min intervals(sensible_heat_flux)
• base_time
• Barometric Pressure(atmos_pressure)
• time_offset
• corr_soil_heat_flow_4
• corr_soil_heat_flow_3
• corr_soil_heat_flow_2
• corr_soil_heat_flow_1
• alt
• vapor_pressure_bottom
• soil_heat_flow_4
• soil_heat_flow_5
• temp_air_bottom
• Heat flux, latent, at 1.5-m height, 30-min intervals(latent_heat_flux)
• temp_trh_top
• temp_reference
• temp_air_top
• rh_top_fraction
• lon
• corr_soil_heat_flow_5
• soil_heat_flow_1
• soil_heat_flow_2
• soil_heat_flow_3
• home_signal_30

SGP/EBBR/E19 - Reprocess: E19 EBBR Soil heat Flow Probe #5 Upsidedown

Soil heat flow probe #5 was installed upsidedown at the initial
installation of the EBBR system.  The data from it had the wrong sign.
Site operations personnel reversed its orientation in the soil on August
14, 1997, thereby correcting the problem.

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 reversing the
sign of cshf5, adding it to ces5 and recomputing the average soil heat flow,

ave_shf = (g1 + g2 + g3 + g4 + g5)/5

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

h = -(e + ave_shf + q).

• soil_heat_flow_5_mv

• soil_heat_flow_5
• surface_soil_heat_flux_5
• Heat flux, latent, at 1.5-m height, 30-min intervals(latent_heat_flux)
• Average soil heat flow at the surface(surface_soil_heat_flux_avg)
• corr_soil_heat_flow_5
• Heat flux, sensible, at 1.5-m height, 30-min intervals(sensible_heat_flux)

SGP/EBBR/E19 - Battery Voltage Drop

EBBR battery voltage at E19, El Reno, OK declined to lower than acceptable
levels after long periods of clouds after initial installation.  The low
voltage condition worsened as Autumn progressed.  In November 1997 the
battery tested okay, but would not hold sufficient capacity at night or
during extended periods of clouds to keep the voltage high enough for the
EBBR to work properly.  At my request, the battery was replaced with a brand
new battery on 31 December 1997.  The new battery is presently maintaining
voltage level at night.

The voltage dropped to 10 volts or less many days before the battery change.
Voltages less than 10.3 volts affected a wide range of measured values, but
at different times.  When the voltage was much below 10 volts the home
signal became very large (several volts), a quirk of the AEM circuitry.
At various times, latent and sensible heat fluxes, soil temperature, air
temperature, relative humidity, vapor pressure, wind direction, soil heat
flux plate output, home signal, and atmospheric pressure (at least) were not
reported correctly by the CR10 datalogger.  At least the sensible and latent
heat fluxes should be considered to be incorrect when the battery voltage is
less than 10.3 volts.  The battery voltage is found in the 15 minute data.

• soil_temp_4_rr
• battery_voltage
• rh_right_mv
• soil_temp_1_rr
• soil_temp_2_rr
• temp_trh_right_rr
• home_signal
• temp_air_left
• atmos_pressure_mv
• soil_temp_3_rr
• rh_left_mv
• wdir_vec_mean_mv
• soil_temp_5_rr
• temp_trh_left_rr
• temp_air_right

• temp_trh_top
• wdir_vec_std
• rh_top_fraction
• rh_bottom_fraction
• temp_trh_bottom
• Barometric Pressure(atmos_pressure)
• Wind direction, vector, lower, 1-min avg(wdir_vec_mean)
• vapor_pressure_top
• temp_air_bottom
• home_signal
• vapor_pressure_bottom
• temp_air_top
• Wind speed vector mean(wspd_vec_mean)

• home_signal_15
• vapor_pressure_top
• Wind direction, vector, lower, 1-min avg(wdir_vec_mean)
• temp_trh_bottom
• soil_temp_5
• soil_temp_1
• soil_temp_2
• soil_temp_3
• soil_temp_4
• wdir_vec_std
• rh_bottom_fraction
• Wind speed vector mean(wspd_vec_mean)
• Heat flux, sensible, at 1.5-m height, 30-min intervals(sensible_heat_flux)
• Barometric Pressure(atmos_pressure)
• corr_soil_heat_flow_4
• corr_soil_heat_flow_3
• corr_soil_heat_flow_2
• corr_soil_heat_flow_1
• vapor_pressure_bottom
• soil_heat_flow_4
• soil_heat_flow_5
• temp_air_bottom
• Heat flux, latent, at 1.5-m height, 30-min intervals(latent_heat_flux)
• temp_trh_top
• temp_air_top
• rh_top_fraction
• corr_soil_heat_flow_5
• soil_heat_flow_1
• soil_heat_flow_2
• soil_heat_flow_3
• home_signal_30

SGP/EBBR/E19 - Noisy Sensible and Latent Heat Fluxes

"Noisy" sensible and latent heat fluxes often occur during daytime periods
when the net radiation is smaller (less than 150 watts/m2), but this is not
the only condition under which it occurs.  During this condition especially,
the temperature gradient, RH gradient, and thus the vapor pressure
gradient are near zero; this causes the sensible and latent heat flux gradients
to be inaccurately calculated.  Good examples of these conditions occurred
on 28 December 1997 and 6 January 1998.  However, even when there is
substantial net radiation the problem does sometimes occur; good examples of
this are found during daytime or nighttime variously on 1, 2, 3, and 4
January 1998.  The conditions occur more fequently than at other EBBR sites;
they do occur at other EBBR sites, but less frequently.

• net_radiation_mv

• Radiation, net(net_radiation)

• Heat flux, latent, at 1.5-m height, 30-min intervals(latent_heat_flux)
• Radiation, net(net_radiation)
• Heat flux, sensible, at 1.5-m height, 30-min intervals(sensible_heat_flux)

SGP/EBBR/E19 - 3-Month Check

During EBBR 3 month checks the Automatic Exchange Mechanism is disabled
(reflected by home signals near zero) so that the two aspirator units can be
placed at the same height.  The measurements during these periods 
do not produce correct outputs of bowen ratio (bowen), sensible heat flux
(h), or latent heat flux (e), nor do the air temperature and relative 
humidity measurements indicate correct gradients.  Checks performed before 
or after the AEM is disabled also lead to some incorrect data.  Incorrect 5,
15 minute and half hour data occurs for the period indicated.

• temp_air_left
• rh_right_mv
• rh_left_mv
• temp_trh_left_rr
• temp_trh_right_rr
• temp_air_right

• temp_trh_bottom
• temp_trh_top
• vapor_pressure_top
• temp_air_bottom
• vapor_pressure_bottom
• temp_air_top
• rh_top_fraction
• rh_bottom_fraction

• vapor_pressure_top
• temp_trh_bottom
• vapor_pressure_bottom
• temp_air_bottom
• Heat flux, latent, at 1.5-m height, 30-min intervals(latent_heat_flux)
• temp_trh_top
• temp_air_top
• rh_top_fraction
• rh_bottom_fraction
• bowen_ratio
• Heat flux, sensible, at 1.5-m height, 30-min intervals(sensible_heat_flux)