## 322-27

## Poster Number 1431

See more from this Division: SSSA Division: Soil Physics and Hydrology

See more from this Session: Soil Physics and Hydrology: II

Tuesday, November 17, 2015

Minneapolis Convention Center, Exhibit Hall BC

##### Abstract:

The dual probe heat pulse method uses two parallel rods and a pulse of heat applied to one rod to estimate soil volumetric heat capacity and hence volumetric water content. The water content has a known relation to the heat capacity. The finite diameter of the rods causes significant errors at low water content. We provide a correction to the measurement of soil volumetric heat capacity (and soil water content) using a dual probe device with pulsed heating, to allow for rods of finite radius and heat capacity. The correction is based on the spatial weighting function of Knight

*et al*. (2007) and checked using the identical cylinders perfect conductor theory of Knight*et al*. (2012), as done by Knight and Kluitenberg (2013) for instantaneous heating. They derived a solution of the forward problem in the Laplace transform domain and inverted it numerically. The spatial weighting function theory for probes of zero radius provides an approximate method of calculating the apparent measured heat capacity of the soil-probe system as a weighted average of the heat capacity of the rods and the heat capacity of the surrounding soil, with the weights calculated by numerical integration and dependent on the probe radii and the dimensionless heating duration. The weights need only be calculated once for a given probe geometry and dimensionless heating duration. This formula can easily be inverted to give a simple correction procedure which gives the soil thermal capacity from the measured apparent thermal capacity of the probe soil mixture and the known probe heat capacity. As expected, a larger correction is necessary for dry soil than for wet soil, and the correction is zero when the soil and probe heat capacities happen to be the same.See more from this Division: SSSA Division: Soil Physics and Hydrology

See more from this Session: Soil Physics and Hydrology: II