Water vapor observations with SAR, microwave radiometer and GPS: comparison of scaling characteristics

The knowledge of spatial distributions of water vapor is very important in atmospheric studies. Often satellite observations, for instance AVHRR, are used to study spatial distributions of water vapor. This method, however, has a limited spatial resolution of about 1 km and does not cover the entire atmospheric column. An alternative way to estimate the spatial behavior of the water vapor is to use temporal observations of the wet delay as given by GPS systems and water vapor paths as measured by microwave radiometers (MWR). These measurements can provide us, under certain conditions, with high-resolution spatial observations of water vapor. Recently, a new technique for atmospheric monitoring was proposed – based on differential satellite interferometric synthetic aperture radar (InSAR) delay measurements. This new method allows for high-resolution full column atmospheric mapping. In this article we focus on the comparison of scaling properties of water vapor as measured with SAR interferometry, GPS and microwave radiometer. We show that under current processing conditions the GPS time series do not provide a useful tool for studying scaling properties of water vapor. The MWR and InSAR, on the other hand, prove to be very useful instruments for this study.