Date of Award
Master of Science
Brian K. Hornbuckle
Soil moisture is a small but very active part of the hydrologic cycle. Recently many studies and reviews have been conducted on its impacts on climate change and short-term forecasting. Satellites could be used as a means for monitoring global soil moisture evolution. In November, 2009, the European Space Agency launched the first satellite dedicated to measuring soil moisture: Soil Moisture Ocean Salinity (SMOS). NASA is planning on launching its own satellite that will incorporate both a passive sensor (like SMOS) and an active sensor in hope of increasing the spatial resolution of the measurements. From September 23, 2008 (DOY266) through September 25, 2008 (DOY268), an aircraft equiped with both a passive and active sensor (PALS) flew over the Iowa Validation Site (IVS) making measurements of the soil moisture through a soybean canopy. At the same time, micrometeorological and soil data were collected. This research used the data from the active (radar) sensor to determine the effect of dew and intercepted precipitation upon the backscatter values. After the effect had been determined, the observed values were modeled and a correction for the dew was determined.
At this time in the season, the soybean canopy had begun senesence. Using the micrometeorological and soil data, an energy and water balance were performed on the IVS to determine if the senesence could be detected and to follow the changes within the field over the time period. It was determined that the water budget indicated a net storage over the system instead of the net loss that was anticipated.
The effects of the intercepted precipitation and dew were determined to have a significant effect upon the radar backscatter. The next step was to determine if this effect could be modeled and how much error it could cause. A semi-empirical backscattering model was used to do this. The model was fitted to the data collected at the IVS before being used to determine what correction needed to be made for the dew effect. The dew correction used was twice the dew amount added to the vegetation water content. This correction was not enough to fully correct for the dew effect but did reduce the error from the dew.
Eric Scott Russell
Russell, Eric Scott, "Effect of dew and intercepted precipitation on radar backscatter of a soybean canopy" (2011). Graduate Theses and Dissertations. 12093.