399
17
Global Soil Moisture
Estimation Using
Microwave Remote
Sensing
Yang Hong, Sadiq Ibrahim Khan,
Chun Liu, and Yu Zhang
17.1 INTRODUCTION
Soil moisture variability, both in space and time, plays a key role in global water
and energy cycles. Soil moisture is a key control on evaporation and transpiration at
the land–atmosphere boundary; thus, real-time monitoring of soil moisture dynamics is very useful not only for understanding land surface–atmosphere interactions
but also for water and climate studies. In addition, regional drying and wetting of
soil moisture trends have profound impacts on climate variability, agricultural sustainability, and water resources management (Jackson et al. 1987; Topp et al. 1980;
Engman 1991). Soil moisture is especially important in arid or semiarid regions, as
it is the critical hydrologic parameter for effective water resource management in
these environments. However, unlike other hydrologic variables such as precipitation, soil moisture observations are not readily available with the required space and
time coverage for global studies. In situ measurements of soil moisture are currently
CONTENTS
17.1 Introduction .................................................................................................. 399
17.2 Microwave Remote Sensing of Soil Moisture ..............................................400
17.2.1 Active Microwave Remote Sensing of Soil Moisture .......................400
17.2.2 Passive Microwave Remote Sensing of Soil Moisture ..................... 401
17.3 Current and Future Satellite Soil Moisture Missions ................................... 401
17.3.1 AQUA AMSR-E Global Daily Soil Moisture Measurements .......... 401
17.3.2 SMOS Mission ..................................................................................402
17.3.3 SMAP Mission..................................................................................403
17.3.4 Some Other Active Soil Moisture Sensors .......................................404
17.4 Hydrological Applications of Soil Moisture Products ..................................405
17.5 Conclusions ..................................................................................................406
References ..............................................................................................................407
17
Global Soil Moisture
Estimation Using
Microwave Remote
Sensing
Yang Hong, Sadiq Ibrahim Khan,
Chun Liu, and Yu Zhang
17.1 INTRODUCTION
Soil moisture variability, both in space and time, plays a key role in global water
and energy cycles. Soil moisture is a key control on evaporation and transpiration at
the land–atmosphere boundary; thus, real-time monitoring of soil moisture dynamics is very useful not only for understanding land surface–atmosphere interactions
but also for water and climate studies. In addition, regional drying and wetting of
soil moisture trends have profound impacts on climate variability, agricultural sustainability, and water resources management (Jackson et al. 1987; Topp et al. 1980;
Engman 1991). Soil moisture is especially important in arid or semiarid regions, as
it is the critical hydrologic parameter for effective water resource management in
these environments. However, unlike other hydrologic variables such as precipitation, soil moisture observations are not readily available with the required space and
time coverage for global studies. In situ measurements of soil moisture are currently
CONTENTS
17.1 Introduction .................................................................................................. 399
17.2 Microwave Remote Sensing of Soil Moisture ..............................................400
17.2.1 Active Microwave Remote Sensing of Soil Moisture .......................400
17.2.2 Passive Microwave Remote Sensing of Soil Moisture ..................... 401
17.3 Current and Future Satellite Soil Moisture Missions ................................... 401
17.3.1 AQUA AMSR-E Global Daily Soil Moisture Measurements .......... 401
17.3.2 SMOS Mission ..................................................................................402
17.3.3 SMAP Mission..................................................................................403
17.3.4 Some Other Active Soil Moisture Sensors .......................................404
17.4 Hydrological Applications of Soil Moisture Products ..................................405
17.5 Conclusions ..................................................................................................406
References ..............................................................................................................407