17. Application of the Apparent Thermal Inertia Concept for Soil Moisture Estimation in Agricultural Areas

The objective of this study is to infer information on Soil Moisture Content (SMC) in agricultural areas using daily gradient of brightness temperature and albedo from MODIS AQUA, based on the so-called apparent thermal inertia (ATI) approach. The developed algorithm has been validated over two different test sites in Italy, Emilia Romagna and South Tyrol regions, and one test site in France, the Pyrenees region, where ground truth measurements were available. For the Emilia Romagna and the Pyrenees test sites, the obtained ATI values were well correlated with SMC values. For the South Tyrol test site, due to large heterogeneity in the mountain landscape, the correlation between ATI and SMC was relatively weak. Cloud coverage which reduces the number of available observations and the vegetation cover which decreases the sensitivity of ATI to SMC were the main limitations in all analyzed test sites. This study showed that a combination of data with a frequent revisit time and polar orbiting sensors can alleviate the impact of cloud coverage on the retrieval. In fact, a comparison between ATI derived from MSG (Meteosat Second Generation) SEVIRI (Spinning Enhanced Visible and Infrared Imager) and MODIS indicated a good correlation between the two estimates thus demonstrating the potential of a possible synergy between the two sensors.