Soil moisture assessment from MODIS data

Soil moisture is important for its role in the soil surface energy balance, since it can control the availability of latent heat flux, the crop development and yield production. Assessing soil moisture, even with the recent wide-spread application of the dielectric devices is a time consuming and laborious endeavor. Thus, this study evaluates the capability of soil water content predicted from remote sensing to indicate the soil/canopy water content at short time and space scale, through comparisons with daily soil moisture data determined in situ, using dielectric devices. Daily aqua moderate resolution imaging spectroradiometer normalized difference vegetation index (NDVI) and the diurnal (daytime and nighttime) land surface temperature (DLST) difference are employed to retrieving daily volumetric soil moisture content (theta) at Sparta experimental field, during the growing season (May-October), of the years 2010, 2011, 2012 and 2014. The concept of apparent thermal inertia (ATI), based on the DLST data, is used for estimating the remotely sensed top soil moisture saturation index (SMSI). Daily soil moisture content (theta(SMSI)) is then obtained from ATI maximum-and minimum-value and the volumetric saturated and residual soil moisture content,theta(sat) and theta(res), respectively, and is compared with the experimental values of volumetric soil moisture content (SM) measured at various depths (10, 20, 30, 40, 60, 80 and 100 cm). Simple relationships are also calibrated between SM and DLST or ATI or NDVI during the years 2010, 2011 and 2014. These are tested for predicting theta (theta(DLST) or theta(ATI) or theta(NDVI), respectively) during the year 2012. First, theta(SMSI), as well as,theta(ATI) or theta(DLST) or theta(NDVI) predict. satisfactorily, as compared with the measured SM. Hence, they can offer a considerable guidance toward applying a rational and sustainable irrigated agriculture and other related fields. The predictions of theta are also especially tested, during the summer period (June-August) and the obtained results are equally satisfactory.