Mixed pixel retrieval of soil moisture from L-band passive microwave observations

Nan Ye
Soil moisture plays a key role in the water, energy, and carbon exchanges at the interface between the atmosphere and earth surface. Its spatial and temporal distributions at regional and global scales are required by many disciplines, including hydrology, meteorology, and agriculture. During the last three decades, passive microwave remote sensing has been widely acknowledged as the most promising technique to measure the spatial distribution of near surface (top few centimetre) soil moisture,
more » ... due to its direct relationship to the soil dielectric constant, its ability to penetrate clouds, and its reduced sensitivity to vegetation canopy and surface roughness. Therefore, the first two space missions dedicated to soil moisture, the Europe Space Agency (ESA)'s Soil Moisture and Ocean Salinity (SMOS) mission and the National Aeronautics and Space Administration (NASA)'s Soil Moisture Active Passive (SMAP) mission, are based on L-band (~1.4 GHz) passive microwave observations every two to three days. Using radiative transfer models, brightness temperature observations are used to estimate water content of the top approximately five centimetres soil with a target accuracy of ~0.04 m3/m3. Based on the current level of antenna technology, the best spatial resolution that can be achieved at L-band by both the SMOS and SMAP radiometer approaches is approximately 40 km. At such a coarse scale, non-soil targets such as surface rock, urban areas, and standing water are present within many SMOS and SMAP pixels across the world, potentially confounding the radiometric observations, and in turn degrading the soil moisture retrieval if not accounted for their contribution. Consequently, the objective of thesis is to determine the impact of land surface heterogeneity conditions on L-band passive microwave satellite footprints using airborne passive microwave brightness temperature observations collected during five Australian airborne field campaigns conduced within the past eight years. Using the Polarimetric L-band Multi-beam R [...]
doi:10.4225/03/58b3a1124bcd9 fatcat:hqxn6dvh45bbdkgwvavgy4gizi