Scientists at VanderSat in collaboration with USDA and NASA recently published a study in which the quality of satellite soil moisture retrievals around the peak temperatures of the day significantly improved. Daily soil moisture data is generally retrieved through satellite observations made during the night or early in the morning. The reason for this relates to the thermal equilibrium theory which states that the temperatures of the soil and vegetation are balanced at night. This is in contrast with observations around the daily peak temperatures because the vegetation experiences a cooling effect that is absent for the soil, which reduces the quality of soil moisture retrievals during the day.
In this recent study, we re-calibrated an existing relation that better accounts for the processes related to this thermal equilibrium theory. A unique feature of this study is the total number of independent verification techniques that were used, and which all confirm each other. These include a data assimilation technique, a statistical approach and the traditional comparison against ground data.
This study revealed an overall improvement in the order of 16% when compared to the soil moisture retrievals that are currently publically available through the NASA data portal (e.g. http://reverb.echo.nasa.gov/reverb/ ). This study offers a first step towards sub-daily soil moisture data products of which a range of applications can benefit from, including weather prediction, flood forecasting, and water management.
Link to this study: http://www.mdpi.com/2225-1154/4/4/50/html