**Estimation Techniques**

**Chapter 2**

Provisional chapter

**Thermal Inertia-Based Method for Estimating Soil**

DOI: 10.5772/intechopen.80252

Thermal inertia is a parameter that characterizes a property of soil that is defined as the square root of the product of the volumetric heat capacity and thermal conductivity. Both properties increase as soil moisture increases. Therefore, soil moisture can be inversely determined using thermal inertia if a relationship between the parameters is obtained in advance. In this chapter, methods for estimating surface soil moisture using thermal inertia are comprehensively reviewed, with emphases on the followings: How thermal inertia is retrieved accurately from a surface heat balance model, and how it is accurately converted to surface soil moisture. In addition, the advantages and disadvantages of the thermal inertia methods are discussed and compared to microwave-based methods, such as spatial resolution and the sky conditions. Precise and accurate data from earth observing satellites are indispensable for estimating the spatial distribution of thermal inertia at a high resolution. On the other hand, data assimilation methods are rapidly developing, which may be competitive with thermal inertia methods. Finally, applications of thermal inertia methods are described and discussed for future explorations, such as dust emission in relation to soil moisture, and estimating regional water budgets by combining other

Keywords: thermal inertia, soil moisture, thermal-infrared band, land surface

temperature, earth observing satellite, surface heat balance, force-restore model, Fourier

Thermal inertia P is one of the parameters used to characterize the thermal properties of soil and is defined as the square root of the product of the volumetric heat capacity C and thermal

> © 2016 The Author(s). Licensee InTech. This chapter is distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/3.0), which permits unrestricted use, distribution, and eproduction in any medium, provided the original work is properly cited.

© 2018 The Author(s). Licensee IntechOpen. This chapter is distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/3.0), which permits unrestricted use,

distribution, and reproduction in any medium, provided the original work is properly cited.

Thermal Inertia-Based Method for Estimating Soil

**Moisture**

Moisture

Dai Matsushima

Abstract

satellite data.

conductivity λ, which is given as

series expansion, microwave-based method

1. Introduction: thermal inertia of unsaturated soil

Dai Matsushima

Additional information is available at the end of the chapter

Additional information is available at the end of the chapter

http://dx.doi.org/10.5772/intechopen.80252

#### **Thermal Inertia-Based Method for Estimating Soil Moisture** Thermal Inertia-Based Method for Estimating Soil Moisture

DOI: 10.5772/intechopen.80252

#### Dai Matsushima Dai Matsushima

Additional information is available at the end of the chapter Additional information is available at the end of the chapter

http://dx.doi.org/10.5772/intechopen.80252

### Abstract

Thermal inertia is a parameter that characterizes a property of soil that is defined as the square root of the product of the volumetric heat capacity and thermal conductivity. Both properties increase as soil moisture increases. Therefore, soil moisture can be inversely determined using thermal inertia if a relationship between the parameters is obtained in advance. In this chapter, methods for estimating surface soil moisture using thermal inertia are comprehensively reviewed, with emphases on the followings: How thermal inertia is retrieved accurately from a surface heat balance model, and how it is accurately converted to surface soil moisture. In addition, the advantages and disadvantages of the thermal inertia methods are discussed and compared to microwave-based methods, such as spatial resolution and the sky conditions. Precise and accurate data from earth observing satellites are indispensable for estimating the spatial distribution of thermal inertia at a high resolution. On the other hand, data assimilation methods are rapidly developing, which may be competitive with thermal inertia methods. Finally, applications of thermal inertia methods are described and discussed for future explorations, such as dust emission in relation to soil moisture, and estimating regional water budgets by combining other satellite data.

Keywords: thermal inertia, soil moisture, thermal-infrared band, land surface temperature, earth observing satellite, surface heat balance, force-restore model, Fourier series expansion, microwave-based method
