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|South Tower Setup|
|1||Central [approx}||36° 48.091'N||118° 09.601'W||1155|
|2||South||36° 44.015'N||118° 07.376'W||1141|
|3||West||36° 45.595'N||118° 14.842'W||1529|
Each of the tower sites had a 110' (34m) tower with instrumentation every 5m. These are:
In addition, the Central site had:
Finally, the West site had an MetOne Model 9012 6-channel particle counter at 5m for comparison to the REAL lidar backscatter.
The 15m sonic at central usually didn't restart itself when power went out. On occasions that this happened (usually due to batteries draining overnight), it was manually restarted when staff arrived in the morning. Thus, there are some outages of 2-4 hours on some mornings.
Please follow the link under "Height.site" to view a tilt plot of the sonic anemometers.
|Height.Site||Boom Angle (deg rel N)||Lean (deg)||Lean Azimuth (deg)|
|5m.c (located on hot-film tower)||85||3.3||-8.8|
The boom angles have been applied to the data, so winds are now in geographic coordinates (+u = wind blowing to East; +v = wind blowing to North; +w = upward). The tilt corrections have not been applied, to keep data from all towers in a similar reference frame (gravitational vertical). Note that fluxes from West (with tilt angles of ~4 degrees) will require some thought to interpret.
The krypton at central.5m output the lowest signal levels. Thus, this was deliberately sited where the Li7500 also was reporting humidity fluctuations. However, this sensor reported values that were higher than those seen during pre-experiment laboratory calibrations (and post-experiment calibrations were not done for this sensor). Therefore, we have chosen to adjust the V0 value for this sensor to an arbitrary value higher than that usually seen in the field. This choice only affects the offset of the calibrated value, so fluxes will not be affected.
Values of sensible and latent heat flux derived from the measured sonic w, virtual temperature, and krypton hygrometer have been added to the NetCDF files where kryptons were installed.
|Cleaning water vapor sensorat 30 meters on central tower|
March 20th, 2006: ~17:00-00:00 (intermittent rain occured at all sites)
April 3rd, 2006, ~13:00 - April 4th, 2006, ~11:00 (intermittent rain occured only at west site only)
April 4th, 2006, ~15:00 - April 5th, 2006, ~1:00 (intermittent rain occured at all sites)
Longwave radiation values calculated from the measured Rpile, Tcase, and Tdome values have been added to the NetCDF files. (Note that the Kipp\&Zonen pyrgeometers do not have Tdome sensors.)
A data logger programming error caused us to not record Tcase values from the main 4-component stand pyrgeometers at central. This was corrected on 14 March. Tcase data before then have been removed. Note that Rlw will also be missing during this period. We advise users who need 4-component radiation values (e.g. to compute the surface energy balance) to use Rlw values from the 10m sensors instead during this period.
The radiation sensors were routinely cleaned, which at times may have caused some spikes in the data. Those bad data caused by interference were removed from the NetCDF files. There was one other unusual spike in the Rlw data during a 30-minute period on the west tower that was removed.
The wind speed correction recommended by Campbell Scientific for the net radiometers has been implemented, using winds measured at 5m and using an assumed displacement height (d, 2/3 of an estimated canopy height H) and a roughness length (z0) calculated from the 100 hours of near neutral cases [|z/L|<0.01] ) to reduce them to the radiometer height of about 1.7m.
|Site||H (cm)||d (cm)||z0 (cm)|
The second lab tests used a digital scale whose readout was recorded continously. This was done to avoid sampling errors, since the entire sample was weighed. However, the scale was limited to samples less than 1kg, so a smaller volume 28cmx10cmx4cm was used. The sample was prepared the same way as above.
The results from these reference measurements are shown here along with the reference calibration from the Ech2o manual. The results are not consistent. West's values are resonably consistent, with agreement between the manual gravimetric measurements both in the lab and in the field, and the same zero moisture value for all measurements. Values at high moisture levels (near field capacity) seemed inconsistent with the other values and were rejected from the fit -- especially since the field measurements were at low moisture levels. The automatic laboratory measurements were always lower than the manual measurements for West.
For South, the automatic measurements again were lower than those taken manually, except for one manual measurement at 4% moisture that was taken after the probe was inserted, but before the water was added. This reading is below the manufacturer zero intercept value, but is similar to that measured in the field. We conclude that the probe needed to be "wet-seated" into the soil type present at South and, in the dry conditions that occurred during TREX, the probe never had proper contact with the soil. (This is the reason that values observed in the field using the Decagon calibration were always negative.) We have included these data in the final data set to show the slight drying trend, but obviously they should not be used quantitatively! As the field gravimetric measurements showed Qsoil values of 2-3%, and significant rain did not appear to occur at this site, we would advise using a constant value of 2.5% for the experiment.
At Central, the automatic measurements clearly do not make sense. We conclude that the volume used was insufficient to perform a calibration (and thus are suspicious of the automatic measurements for West and South, as well). The soil appeared to have a much larger clay contact than at the other sites which held moisture even though the surface skin often cracked. This sample was dried much longer than the others (even in an oven at 45 degC) and never got much below 20%. In this case, we are also suspicious that the field gravimetric samples might not have been given sufficient time to dry. (Our standard field procedure is to dry for 24 hours at 100 degC.)
Thus, we conclude that the only measurements useful for calibration are the manual lab measurements, and even these excluding the range near field capacity. The fits derived from this subset of the calibrations have been used in the final processing of these data.
Data from the logger used at the main 4-component radiation stand at central were intermittently corrupted by the radio link that was used. Various soil values (mostly Qsoil) were affected by this problem. An attempt to implement a generic correction was not successful. Thus, the data have been despiked and values with large jumps removed. This resulted in the loss of about 14% of the samples, which should not have a noticable impact on the data from these slow-response sensors.
Rain was logged at the base trailer on the night of 27 Feb. The data at Central appear to be reasonable through this rain, though not much change is seen. The data at West clearly change a lot, so the data prior to the rain have been assumed to indicate that the probe was not well seated into the soil and have been removed. Raw data from South prior to the rain were not recorded.
Values for the soil heat capacity, thermal diffusivity, and thermal conductivity derived from the TP01 readings have been added to the NetCDF files.
There were two separate wiring problems that occurred at West, causing at least 2 weeks of data outages in both March and April. These data cannot be recovered and any spurious values have been removed.
At both West and South, the TP01 readings changed abruptly, presumably associated with rain at 6 April. Since it is unlikely that this was due to a true change in properties, it probably reflects better contact of the probe with the soil after wetting [though Qsoil didn't change much]. We have decided not to remove these data from the archive, but the latter values probably are correct.
|Station||Date;Time (PDT)||TRIME (%)||Depth (cm)||Gravimetric (%)||Density (g/cm^3)|
The tables display mean, deviation, number of missing values, and number of clipped values for each variable, from 0:00-6:00, 6-12:00, 12-18:00 and 18-24:00 each day.
The 5 minute statistics for most variables are shown on time-series plots.
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This page was prepared by Gordon Maclean and NCAR EOL In-Situ Facility