ATMOSPHERIC WATER VAPOR MAPPING BY COMBINING INTERFEROMETRIC SYNTHETIC APERTURE RADAR AND GPS OBSERVATIONS

In this paper, a new approach developed to retrieve temporally-differenced maps of the spatial distribution of water vapor from interferometric synthetic aperture radar (InSAR) data with a horizontal resolution as fine as 20 m is described. To get a more accurate map of wet delay, we used the ERA-Interim to predict the dry delay component in the total atmospheric delay from InSAR. In addition, the ERA-Interim was used to compute the conversion factors required to convert the wet delay to precipitable water vapor (PWV). The InSAR-derived differential PWV maps were calibrated by means of the ground-based GPS PWV measurements. The approach was applied to map the temporal change of PWV over the Southern California, USA. We validated our results against measurements of the PWV acquired from a Medium-Resolution Imaging Spectrometer (MERIS) onboard the ENVISAT satellite. The results show strong spatial correlation with values of uncertainty of less than 2 mm.