| Start Date | Start Time | End Date | End Time | Data Quality Metric |
|---|---|---|---|---|
| 02/05/1996 | 0000 | Open Ended | 0000 | Suspect |
| Subject: | SGP/SWATS (All) - Similar Soil Temperature Trends At Soil Depths Below 15 cm; Exaggerated |
| DataStreams: | sgpswatsE18.a1, sgpswatsE1.b1, sgpswatsE6.b1, sgpswatsE8.a1, sgpswatsE9.a1, sgpswatsE12.b1, sgpswatsE7.b1, sgpswatsE15.b1, sgpswatsE6.a1, sgpswatsE32.b1, sgpswatsE7.a1, sgpswatsE12.a1, sgpswatsE4.b1, sgpswatsE2.b1, sgpswatsE20.b1, sgpswatsE34.b1, sgpswatsE19.b1, sgpswatsE13.b1, sgpswatsE19.a1, sgpswatsE27.b1, sgpswatsE25.a1, sgpswatsE11.a1, sgpswatsE33.b1, sgpswatsE37.b1, sgpswatsE4.a1, sgpswatsE18.b1, sgpswatsE13.a1, sgpswatsE36.b1, sgpswatsE3.b1, sgpswatsE9.b1, sgpswatsE20.a1, sgpswatsE15.a1, sgpswatsE16.a1, sgpswatsE22.a1, sgpswatsE38.b1, sgpswatsE22.b1, sgpswatsE5.a1, sgpswatsE11.b1, sgpswatsE31.b1, sgpswatsE3.a1, sgpswatsE16.b1, sgpswatsE8.b1, sgpswatsE1.a1, sgpswatsE24.b1, sgpswatsE25.b1, sgpswatsE10.a1, sgpswatsE24.a1, sgpswatsE2.a1, sgpswatsE10.b1, sgpswatsE35.b1, sgpswatsE5.b1 |
| Description: | At all SWATS locations, all soil levels below 15cm show essentially the same magnitude of soil temperature change on a daily basis and at the same times as the 15cm level, with no delay at greater depths. This does not represent physical reality at these depths. Furthermore, this behavior began with the very first installation of the SWATS and has been seen in every SWATS system. However, the magnitude of this problem is much greater at extended facilities E31 through E38. Comparison of the SWATS with co-located SEBS or EBBR 5cm soil temperatures shows that the diurnal trend of soil temperature at 5cm is similar for the SWATS and the EBBR or SEBS, but usually exhibits a larger maximum and a lower minimum. The SWATS minimum also is reached less smoothly than the EBBR or SEBS. This is likely because the SEBS and EBBR soil temperature measurements are an integration from the surface to 5cm depth. The SWATS pattern is also seen, to a much more minor extent, in the trise, trise_ref, water content, soil water potential, and fractional water index measurements at 15cm and below; however, the variation in these measurements is well within the uncertainty of the measurements. It appears that the SWATS probe thermistor lead connections with the datalogger terminal strip were acting as thermocouples. Why the effect was so much greater at E31-38 is not clear, but it probably has something to do with how the lead connections to the datalogger were performed. This situation particularly affects the measurements during daytime hours, and corresponds with heating of the SWATS enclosure by the Sun. 5cm SWATS soil temperatures are very similar to co-located EBBR or SEBS 1-5 cm integrated temperatures at most extended facilities, and therefore appear to be valid (the solar heating/thermocouple effect may be swamped by the actual soil temperature diurnal change). 15cm SWATS soil temperatures may also be valid at extended facilities other than E31-38, as they show a larger diurnal variation than lower depths and about midway in magnitude between the 5cm and 25 cm measurements. Since it seems likely that the soil temperature measurements below 15cm were affected by the solar heating of the enclosure at all but E31-38, and at all depths below 5cm at E31-38, individual measurements of soil temperature at these depths during daylight hours, and daily averages of the same, can not be trusted on most (particularly sunny) days. The effect on cloudy days seems smaller. |
| Suggestions: | Use only nighttime SWATS soil temperature measurements to calculate daily average soil temperature for depths below 5cm for extended facilities E31 through E38, and at depths greater than 15 cm for all other extended facilities. Measurements of SWATS 5cm soil temperature are valid for all extended facilities. Measurements at 15 cm are valid for extended facilities other than E31-38. All other SWATS soil temperature measurements are suspect. Use only nighttime SWATS soil temperature measurements to calculate daily average soil temperature for depths below 5cm for extended facilities E31 through E38, and at depths greater than 15 cm for all other extended facilities. Measurements of SWATS 5cm soil temperature are valid for all extended facilities. Measurements at 15 cm are valid for extended facilities other than E31-38. All other SWATS soil temperature measurements are suspect. |
| Measurements: | sgpswatsE32.b1: more
sgpswatsE12.a1: more sgpswatsE1.a1: more sgpswatsE2.b1: more sgpswatsE16.a1: more sgpswatsE13.b1: more sgpswatsE36.b1: more sgpswatsE9.a1: more sgpswatsE22.b1: more sgpswatsE6.b1: more sgpswatsE5.a1: more sgpswatsE25.a1: more sgpswatsE33.b1: more sgpswatsE11.a1: more sgpswatsE2.a1: more sgpswatsE12.b1: more sgpswatsE15.a1: more sgpswatsE16.b1: more sgpswatsE19.a1: more sgpswatsE37.b1: more sgpswatsE7.b1: more sgpswatsE22.a1: more sgpswatsE6.a1: more sgpswatsE3.b1: more sgpswatsE27.b1: more sgpswatsE10.a1: more sgpswatsE11.b1: more sgpswatsE3.a1: more sgpswatsE38.b1: more sgpswatsE15.b1: more sgpswatsE18.a1: more sgpswatsE34.b1: more sgpswatsE19.b1: more sgpswatsE8.b1: more sgpswatsE20.b1: more sgpswatsE7.a1: more sgpswatsE4.b1: more sgpswatsE24.b1: more sgpswatsE31.b1: more sgpswatsE10.b1: more sgpswatsE1.b1: more sgpswatsE13.a1: more sgpswatsE35.b1: more sgpswatsE18.b1: more sgpswatsE20.a1: more sgpswatsE8.a1: more sgpswatsE9.b1: more sgpswatsE5.b1: more sgpswatsE4.a1: more sgpswatsE25.b1: more sgpswatsE24.a1: more |