Delta-K Interferometric SAR Technique for Snow Water Equivalent (SWE) Retrieval

This letter describes the concept of using delta-K technique on interferometric synthetic aperture radar (InSAR) data for deriving the snow water equivalent (SWE) of dry snow-covered ground by utilizing the presence of scatterers in both datasets. The main scattering contribution from a dry snow cover is from the snow-ground interface. Thus, the interferometric phase of two SAR images, one with no snow and one with dry snow cover, contains information on the SWE. By performing a delta-K processing of the two SAR scenes followed by averaging, an estimation of the SWE can be achieved. The first step in the delta-K InSAR processing is to split the band into two nonoverlapping subfrequency band images. The resulting two subband images then contain two new carrier frequencies with a small delta frequency or delta-K separation. The next step is to multiply the two subband images together to obtain the delta-K image, one for summer and one for winter. Finally, the delta-K interferometric SAR image is generated by multiplying the two delta-K images from summer and winter together. In this letter, experimental results using European Remote sensing Satellite 1 (ERS-1) data from a summer and winter situation show that the delta-K phase can be estimated to a few degrees accuracy for an area of 10 x 10 km(2) corresponding to an SWE accuracy of approximately 100 mm.