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Preliminary Results from ATDD’s Soil Moisture/Temperature Testbed Soil Moisture and Soil Temperature Observations and Applications: A Joint U.S. Climate Reference Network (USCRN) – National Integrated Drought Information System (NIDIS) Workshop, Oak Ridge, TN, March 3-5, 2009 William Collins
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Soil Moisture/Temperature Testbed
Soil Moisture and Soil Temperature Observations and Applications: A Joint U.S. Climate Reference Network (USCRN) – National Integrated Drought Information System (NIDIS) Workshop, Oak Ridge, TN, March 3-5, 2009
2000 day 172 of 2007 through 0900 day 100 of 2008
4 holes with temperature and moisture sensors:
3 at 5 cm depth
3 at 10 cm depth
2 at 20 cm depth
1 at 50 cm depth
1 at 100 cm depth
The moisture sensors are Vitel moisture instruments,measuring the dielectric constant to get water content.The water content is given in m3 water/m3.
This study will exclusively examine the characteristics of the soil moisture and temperature data at 5 and 10 cm since only those 2 depths have 3 sensors.
The use of 3 sensors at the same location has proven invaluable in the quality control of temperature and precipitation (from the 3-wire Geonor gauges) for the U. S. Climate Reference Network. This study will take a first look at that utility here.
T2-T1: -0.083 T2-T1: 0.212
T3-T1: -0.260 T3-T1: 1.038
T3-T2: -0.177 T3-T2: 0.875
T2-T1: -0.216 T2-T1: 0.671
T3-T1: -0.296 T3-T1: 0.840
T3-T2: -0.079 T3-T2: 0.648
M2-M1: 0.046 M2-M1: 0.012
M3-M1: -0.001 M3-M1: 0.020
M3-M2: -0.047 M3-M2: 0.012
M2-M1: -0.032 M2-M1: 0.041
M3-M1: -0.062 M3-M1: 0.049
M3-M2: -0.029 M3-M2: 0.046
The moisture during the period of record begins dryand ends wet. The data were divided as follows:
Dry period: 2000 day 172 2007 to 2400 day 295 2007
Wet period: 0100 day 329 2007 to 0900 day 100 2008
Transition period: data in between
The following plots show a comparison of the moisture at 5 and 10 cm depth, individually for each sensor and hole for a selected time period spanning dry to wet.
Individually at 5 and 10 cm Depth
Selected Time Period (Dry to Wet)
Note! Without quality control, the best estimate of the moisture should be the average of the 3 sensor values. The following plots have the 3 sensor values averaged, and in addition, they are smoothed in time with values (0.25, 0.50, 0.25).
Lower Limits for Example Choices (8 s):
5 cm – 0.192
10 cm – 0.184
5 cm – 6.10
10 cm – 5.44
Dry and Wet Periods
For the Same Sensor
Best response would bealone line of slope 1:1, with vertical displacementand sensors from samehole grouped together.
Line has slope 1:1
Between Pairs of Sensors at Hole 1
Full Time Record
Possible use in quality control…
Line is not linear fit; has 1:1 slope.Ideal fit would be along this line.
Since the inter-sensor standard deviation for 1-hour change becomes smaller as the inter-sensor standard deviation becomessmaller, the inter-sensor 1-hour change provides independentinformation for the quality control of soil moisture.
Steeper slope of line for wet period indicateseven greater value of 1-hour change for qualitycontrol than for dry period.