Radar geophysics and new observables
NiSAR, NASA JPLSatellite radar now provides frequent, global observations of Earth’s surface. My work develops the theory and algorithms needed to interpret those measurements reliably, especially where changing soil moisture, vegetation, or surface structure complicates conventional interferometry.
I have developed a geocoded SAR processing approach, a physics-based covariance model for decorrelation noise, and methods that connect closure phase to systematic bias in InSAR time series. This work helps determine when additional interferograms improve precision, how network design affects inferred deformation, and when an apparent error contains information about a changing surface.
My recent research treats closure phase as a geophysical observable. A multilayer scattering model and retrieval method developed with Heresh Fattahi links closure phase to surface soil-moisture variability, with demonstrations in the Mojave Desert and California’s Central Valley. Current work uses multi-frequency NISAR observations to test how radar can improve soil-moisture and irrigation monitoring in the High Plains.
Future work will extend these methods to vegetated and mountainous environments, where temporal decorrelation and atmospheric variability remain major obstacles to measuring hydrologic change and climate-sensitive hazards.
Yujie Zheng
Assistant Professor
I develop satellite radar and geodetic methods to understand how water, the solid Earth, climate variability, and human activity shape the surface and subsurface.
