A Penta-Needle Heat Pulse Probe Array for Subsurface Evaporation and Heat Flux Estimates ASA-CSSA-SSSA Annual Meeting October 2011 Scott B. Jones 1, Masaru Sakai 1,2, Morteza Sadeghi 3 and Markus Tuller 4 1)Dept. Plants, Soils, and Climate, Utah State University 2)Dept. Bioresource Engineering, Mie University, Japan 3)Dept. Water Engineering, Ferdowsi University of Mashhad, Mashhad, Iran 4)Dept. Soil, Water, and Environmental Science, The University of Arizona. USU PHPP development team – Kelly Lewis, James Suisse, Ricardo Estevez, Franyell Silfa, Marcos Chalas, Ricardo Tejeda, Sammy Bhushan

Introduction Sensor Needle Interval Tri-needle HPP 6mm Penta-needle HPP 6mm interval2.75mm interval 27.3 o rotation angle

Introduction Heat Pulse Probe (HPP) Tri-needle Penta-needle array Soil Thermal Properties Subsurface Evaporation Rate Soil Heat Flux

Introduction Subsurface Evaporation Rate (HPP Method) Subsurface Energy Balance Heitman, Xiao, Horton, Sauer, WRR (2008) latent heatSensible heatSensible heat storage

Methods for G Determination Calorimetric: Gradient: Combination: Soil Heat Flux Plates: (Sauer et al., 2003; VZJ) – Heat/hydraulic flow distortion; fixed – Correction for near surface conditions (z > 4cm) – Underestimated G in dry/sat. sand by 39/73%

Objectives Measure Subsurface Evaporation using a PHPP array – and  fitted on PHPP – Sakai, Jones, Tuller Measure Soil Heat Flux using a PHPP array – Compare G from PHPP array with soil heat flux plates Temperature adjustable heat panel

Experimental Setup Room temperature 20 o C Thermocouples + 3 PHPP Heat Panel – Constant surface temp. Heat panel Temperature Controller Sand column Load cell Heat flux plates Penta-needle Heat Pulse Probe Array

Temperature Cycling Material – Wedron (Ottawa) sand Dry Saturated Heat Panel Settings – Fixed temperature (35 o C) – Cycled temperature (30 min on, 120 min off) 25, 30, 35, 40, 45 o C

Uniform Dry/Saturated Sand PHPP TC 3.5 h 1.5 h 0.5 h 0 h Surface Temperature

PHPP-measured T for 3 Depths

Dry 25, 30, 35, 40, 45 o C

Saturated 25, 30, 35, 40, 45 o C

Surface Heat Flux Comparison of heat flux at the soil surface obtained from PHPP calculations and application of the Stefan-Boltzmann Law.

Summary  The PHPP can be combined in an array to provide coupled subsurface evaporation and ‘near-surface’ heat flux estimates.  Heat flux estimates from the PHPP array were generally higher than heat flux plate estimates as expected for both dry and saturated sand.  Additional testing of the PHPP array is ongoing to fully understand the capabilities and limitations of this multifunction sensor.

Acknowledgements The authors gratefully acknowledge support from the USDA Cooperative State Research, Education, and Extension Service supported by a Special Research Grant # and by a USDA-CSREES AFRI Soil Processes Program grant # References Heitman, J.L., X. Xiao, R. Horton, and T.J. Sauer (2008): Sensible Heat Measurements indicating depth and magnitude of subsurface soil water evaporation, Water Resour. Res., 44: W00D05. Sakai, M., S.B. Jones and M. Tuller Numerical evaluation of subsurface soil water evaporation derived from sensible heat balance, Water Resour. Res. 47:W02547.

Copper coils Aluminum plate Plexiglas walls Sand/Soil Styrofoam insulation Plywood box 30 cm 15 cm 10 cm Heat Flux Measurement Apparatus