Comments on “Estimating Soil Water Contents from Soil Temperature Measurements by Using an Adaptive Kalman Filter”

Kun Yang Department of Civil Engineering, The University of Tokyo, Tokyo, Japan

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Toshio Koike Department of Civil Engineering, The University of Tokyo, Tokyo, Japan

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Abstract

A scheme was proposed by Zhang et al. to estimate soil water content from soil temperature measurements by using an adaptive Kalman filter. Their scheme is based on the fact that soil heat capacity and thermal conductivity are a monotonic function of soil water content. However, thermal diffusivity, a more critical thermal parameter in such an estimation, is not a monotonic function of soil water content in most cases. This could result in multiple solutions in some cases when deriving soil water content from soil temperatures.

Corresponding author address: Dr. Kun Yang, River Laboratory, Dept. of Civil Engineering, University of Tokyo, Hongo 7-3-1, Bunkyo-ku, Tokyo 113-8656, Japan. yangk@hydra.t.u-tokyo.ac.jp

Abstract

A scheme was proposed by Zhang et al. to estimate soil water content from soil temperature measurements by using an adaptive Kalman filter. Their scheme is based on the fact that soil heat capacity and thermal conductivity are a monotonic function of soil water content. However, thermal diffusivity, a more critical thermal parameter in such an estimation, is not a monotonic function of soil water content in most cases. This could result in multiple solutions in some cases when deriving soil water content from soil temperatures.

Corresponding author address: Dr. Kun Yang, River Laboratory, Dept. of Civil Engineering, University of Tokyo, Hongo 7-3-1, Bunkyo-ku, Tokyo 113-8656, Japan. yangk@hydra.t.u-tokyo.ac.jp

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