Presentation on theme: "Preliminary Results from ATDD’s Soil Moisture/Temperature Testbed Soil Moisture and Soil Temperature Observations and Applications: A Joint U.S. Climate."— Presentation transcript:
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 email@example.com USCRN
Characteristics of Oak Ridge Data From 2000 day 172 of 2007 through 0900 day 100 of 2008 Instrument Deployment— 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 m 3 water/m 3.
Study Objective 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.
Statistics for Full Time Period by Individual Hole and Depth: Mean Temperature by Sensor Inter-sensor Temperature Differences Distributions (0.2 C bins) Means Standard Deviations (Only a few typical examples are shown.)
Comparison of Moisture for 3 Co-located Sensors The moisture during the period of record begins dry and 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.
Note! Same vertical scale used for all these plots.
Comparison of Average Moisture At 4 Holes 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).
Comparison of Moisture Standard Deviations— Inter-sensor differences versus Inter-sensor 1-hour change differences Individually for Dry and Wet Periods Implications for Quality Control
Since the inter-sensor standard deviation for 1-hour change becomes smaller as the inter-sensor standard deviation becomes smaller, the inter-sensor 1-hour change provides independent information for the quality control of soil moisture.
Summary Preliminary comparison was made between the 3 co-located soil temperature and moisture sensors from nearly 300 days of data from four holes at Oak Ridge, TN. The inter-sensor differences show wide differences in the performance of individual sensors. Also, there are significant differences between the mean values of moisture at the 4 holes at 5 and 10 cm depths. The results have implications for quality control for both temperature and moisture— The use of 3 sensors is invaluable for error and value determination. Sensor value and change in time are both useful for qc. Individual sensor characteristics, if developed, might be valuable. Question for research: Can differences in individual sensor characteristics be linked to calibration, installation, or other factors?