Remote Sensing of Soil Water Content at Large Scales.

Soil water content at the near surface is a critical parameter for understanding land surface atmosphere interactions, influencing surface energy balances.  Using microwave radiometry, an accurate global map of surface soil water content can be generated on a near daily basis.  The accuracy of the products is compared to in situ resources and calibration can result in error standards as low as 0.04 m³/m³.  The resolution of these global surface products vary from 50 km to as small as 3 km in scale with some trade-offs in accuracy.  The scales of these products are useful for weather forecasting and climatology, as well as water managers who operate on county scales or larger.  Current estimates are for the 0-5 cm soil depth which matches with calibrated network installations. As a part of upcoming satellite missions, soil water content will be modeled to a depth of 1 meter for use in agricultural monitoring and forecasting.   A review of past, current, and future satellite missions will be given and future opportunities for research will be discussed.