| Description: | In the original EBBR software (Version 1) for the Campbell CR10 at the Central
Facility (E13), adjustment of the soil moisture for soil type was performed
differently than for the other EBBR systems. This was supposed to have
been changed prior to installation (according to the vendor), but the
change was not made. This adjustment was carried into Version 2 and was
not discovered by the mentor (me) until later. A polynomial is used to
adjust the measured soil moisture for differences between the soil type at
the location of installation (clay-loam assumed) and the soil type (sand)
used in the calibration of the soil moisture sensor. The adjustment in
the E13 EBBR only, was computed on the basis of a sandy-loam soil.
Presently, a clay-loam soil type is assumed for each EBBR location. Soil
types at the extended facilities have not been characterized yet, although
there are hopes of doing so in the future. The effect of using a
polynomial for sandy-loam soil instead of clay-loam soil is to decrease the
resultant soil moisture values by approximately 14.5% when the clay-loam
polynomial would indicate a soil moisture of 28.3%, and by approximately
38.3% when the clay-loam polynomial would indicate a soil moisture of 6.3%.
The normal range of soil moisture at the EBBR sites is approximately 3% to
35%.
The effect of the soil moisture decreases above on the adjustment to soil heat
flux plate measurements is less than 1.0%. The effect on the change in
energy storage in the soil (determined from the change in soil temperature
over time) is a 10% decrease for a soil moisture of 28.3% and a decrease of
13.0% for a soil moisture of 6.3%. The change in energy storage is typically
5% of the total surface energy budget during mid-day and 25% at night.
Therefore, the soil type adjustment error in the Central Facility EBBR
resulted in approximately a 0.5% error in the surface energy budget during
mid-day and 2.5% at night. These are small and acceptable errors and
should not cause one to need to recalculate energy budget values. |