ISFS Data Report

Site locations

Both locations used in this study were in the eclipse path of totality.  They were separated by about 50km, but mostly along a line parallel with the path of the eclipse.

The site labeled "museum" was west of the church at the Stuhr Museum of the Prarie Pioneer.  This was in a grass field with a relatively open fetch to the north and a shorter fetch of 120--300m to trees to the south.

The site labeled "airport" actually was in rangeland.  (By the time we learned that deployment at a nearby airport was not possible, it was too late to change our name for this site!)  This terrain was somewhat rolling, representative of the transition to the Nebraska sand hills.  There were some individual trees in the area, but the fetch was generally open to the north and for about 300m to the south.

We thank the Stuhr Museum Marketing director and the owner of the rangeland site for facilitating our deployments at both of these locations!

Data recovery

There are some gaps in the QC data in the "prelim_qc_geotiltcor" dataset on 20 Aug.  It isn't clear why they are there.  It should be possible to fill them in.

Sensors data processing

Flux Sonic Anemometer

CSAT3 sonic anemometers were used at these sites.  There was one data spike at about midnight on 19-20 Aug at the "airport" that appears to be caused by rain.  It has not been edited.  The orientation of the anemometer was determined with a compass and has been used in the production of the "geo" data set.

Infrared Gas Analyzer (H2O/CO2)

LiCOR LI-7500 open-path infrared gas analyzers were used to help measure the latent heat flux and CO2 flux.  There were spikes again related to rain on 19-20 Aug and apparently due to dew the following 2 nights.  These have not been edited.  (A good start would be to ignore any data when the value of the "Wetness" variable is above 0.19V.)

The mean values for h2o and co2 were not calibrated prior to this project and thus are expected to have large offsets.  The offset in h2o was approximately +1.5 and +3.5 g/m3 for museum and airport, respectively, as compared with the T/RH sensor.  The mean value of co2 at the museum was approximately correct, but at the airport it was very low -- approximately 200ppmV (330mg/m3).  This value has been added to the co2.museum values in the high-rate NetCDF files.  Nevertheless, we expect the fluctuations, and thus the fluxes, to be nearly correct in magnitude.

2-D Sonic Anemometer

We used our standard Gill Wind Observers which operated normally.  The "geo" dataset again has the correct orientation, as measured by compass.

T/RH

Temperatures from our standard T/RH probe were fine.  However, all of the RH values were reported incorrectly.  This was determined to be a problem in the method we used to calibrate these sensors before the project.  (Only one temperature was used, and thus the temperature sensitivity of the RH sensor was unconstrained.)  The post-project calibration was used to create the proper calibration coefficients for these sensors, which were applied in post-processing.  This correction has been done point-by-point using the high-rate data and averaged to create the statistics.  In the high-rate NetCDF data, we have removed all RH values to avoid being misleading.

Barometer

We used our standard Vaisala PTB220 barometers, which generally work well.  However, the museum sensor had spikes, level shifts, and even a data outage.  We suspected heat, but it still is not clear why these problems occurred.  At this site, values reported by the LI-7500's internal barometer have been inserted into the P variable.  At the "airport" the PTB220 was fine.

Radiometer

We used our Hukseflux NR01 radiometers, which operated normally, though we expect values to be off when the Wetness sensor indicates that liquid water may have been present.  These values have not been removed.

Soil sensors

Tsoil

Our standard 4-prong Tsoil was used.  For this project (and Perdigao), our software mishandled these data when the temperature was above 32degC.  We have corrected this issue point-by-point and recalculated the 5-minute averages.  Note that we have not corrected the high rate time series (but this shouldn't matter, since soil temperature is pretty slow response anyway).

Qsoil

We used our standard EC-5 probes, which operated normally.  Gravimetric samples were taken during installation and analyzed a week later in Boulder.  We expected these samples to have dried out, but were surprised to see values within 2% of the station readings.  This could indicate that both were in error (the sites due to probes still settling into the soil, which was an expected source of error).  Alternatively, the gravimetric samples were transported still surrounded by their brass sample core rings which may have prevented them from drying.  In either case, we have no justification for changing the recorded values.  

Gsoil

We used our standard REBS HFT plates, which operated normally.  However, we were unable to apply the Phillip correction, as we normally do, since we did not deploy TP01 sensors to provide a value of the thermal conductivity of the soil.  This correction generally is less than 10%.

Csoil

As mentioned above, all of our TP01 heat capacity sensors were still being shipped back from Perdigao, so we could not directly measure the heat capacity of the soil.  Instead, we have used "book values" from a much earlier experiment in Kansas in the computation of the soil heat storage term.  Our guess is that Kansas and Nebraska soils are somewhat similar.