Title: BALTEX Cabauw Cabauw Soils
Dr. Fred C. Bosveld
Royal Netherlands Meteorlogical Institute
3730AE, De Bilt
tel. +31 (0)30 2206911 (787)
fax +31 (0)30 2210407
1.0 DATA SET OVERVIEW
Contains the soil temperature and soil water content observations at the BALTEX anchor station Cabauw, lat. 51.97N lon. 4.93E, height (m.s.l.) -0.7 m.
This data set contains observations of soil temperature at -0.04, -0.08, -0.12, -0.20, -0.30, and -0.50 m heights starting 26 February 2003 and observations of soil moisture at -0.03, -0.08 and 0.20 m height starting 6 December 2002.
2.0 INSTRUMENTATION DESCRIPTION:
2.1 Soil temperature
Soil temperatures are measured at the soil-terrain 100 m South of the main tower. The temperature needles are burried horizontally at depths of 0.04, 0.08, 0.12, 0.20, 0.30 and 0.50 m.
Instruments are manufactured at KNMI. They are Nickle wired needles with an
electric resistance of 500 Ohm and a sensitive length of 0.35 m. Calibration
is done at KNMI. Datalogging is at a Campbell Scientific CR21X datalogger.
2.2 Soil water content
Soil water content is measured at the soil-terrain, 100 m South of the main tower, with a TDR-sensor at a depth of 0.20 m.
The instruments are manufactured by Campbell Scientific. TypeCS615, principle: Time domain reflectometry, rod length = 30 cm, width between the two rods: 32 mm. Calibration is done by Campbell Scientific. Data logging is with a Campbell Scientific CR21X datalogger. Measurements are taken 5 times in a 10 minute interval. Averages over 10 minutes are saved.
We advise to use the observations only in a qualitative manner. The uncertainty in the observations are unknown. A standard calibration curve is used to transform the sensor output signal into physical values, whereas it is known that TDR observations are influenced by the specific electrical properties of the clay soil. Good indication between wet and dry periods can be obtained from the observations but absolute values may be unreliable.
The observations at 3 and 8 cm depth are within the expected range of soil water content for the soils at Cabauw. The observations at 20 cm are too high by typically a value of 20%.
Currently a calibration program with Cabauw soils from different depths is running at the soil physical Laboratory at of Wageningen University Research, results are expected by the end of 2010
For more information we refer to http://www.knmi.nl/~bosveld -> Observations ->Documentation -> soil water
3.0 DATA COLLECTION AND PROCESSING:
3.1 Data collection
Instruments are logged with a Campbell Scientific CR21X datalogger. Measurements are taken 5 times in a 10 minute interval. Averages over 10 minutes are saved.
3.2 Data processing
These data are in the CEOP EOP-3 data format agreed to by the CEOP Scientific Steering Committee. This format is described in detail as part of the CEOP Reference Site Data Set Procedures Report which is available at the following URL: http://www.eol.ucar.edu/projects/ceop/dm/documents/refdata_report/ceop_soils_format.html
4.0 QUALITY CONTROL PROCEDURES
4.1 Cabauw Quality Control Procedures
After the data are stored in the database a manual (on-eye) check is performed and together with information from the logbook suspect data are rejected.
NCAR/EOL Quality Control Procedures
NCAR/EOL conducted two primary quality assurrance/control procedures on the reference site data. First the data has been evaluated by a detailed QA algorithm that verifies the format is correct, examines any QC flags, and conducts basic checks on data values. Second, EOL conducts a manual inspection of time series plots of each parameter.
5.0 GAP FILLING PROCEDURES
No gap filling is applied
6.0 DATA REMARKS:
Some of the temperature needles showed unstable calibration (a few 0.1 Kelvin). Soil temperature is only available on a continuous basis after the 26th of February 2003. The standard calibration for the TDR sensor as a given by the manufacturer is used. For the clay soil which is the dominating soil type at Cabauw this is not correct. This is the reason that a "D" quality code is used in the file. Soil water content is only available on a continuous basis after the 6th of January 2003.
7.0 REFERENCE REQUIREMENTS:
Users of the data are required to follow the CEOP data policy. Above this users of this data are kindly requested to acknowledge:
"The Royal Netherlands Meteorological Institute"
in any publication in which the data are used. Questions about the data can be directed to the e-mail adress given above. The user is kindly asked to communicate any problem in the data set to the e-mail adress given below. Users are also kindly asked to send a copy of any publication in which the data are used to the adress given above.