Soil moisture from thermal infrared satellite data: Synergies with microwave data

Abstract

Soil moisture is an important geophysical parameter and information on soil moisture is needed by many scientific disciplines in the context of climate modeling, hydrologic modeling, flood and drought forecasting, or in the context of geo-health applications. Changes in soil moisture can be the driver for changes in vegetation cover and might directly impact land use and agricultural yield. A lot of approaches to derive soil moisture from remotely sensed spaceborne earth observation data exist. Most of them are based on the utilization of radar data, such as scatterometer data derived from instruments onboard the ERS satellite (ERS-Scat) or the Advanced Scatterometer onboard of the METOP satellite (METOP-Ascat). Such data comes at resolutions of 50 and 25 km respectively and has the large advantage that it can be acquired independent of solar illumination and cloud cover. Furthermore, several scientists have used higher resolution synthetic aperture radar (SAR) data for soil moisture estimation. It is less well-known that thermal infrared satellite data is also suitable to retrieve soil moisture information. As thermal data usually is available at a higher resolution (1 km and better) it is an attractive alternative to radar data. This chapter presents approaches of soil moisture retrieval from thermal data, and discusses advantages and shortcoming of soil moisture extraction based on this data type. Benefits on a synergistic operational soil moisture product based on both thermal and radar data are discussed.