Submitted to: Society of Photo-Optical Instrumentation Engineers
Publication Type: Proceedings
Publication Acceptance Date: 12/11/2006
Publication Date: 12/11/2006
Citation: Narvekar, P., Heygster, G., Jackson, T.J., Bindlish, R. 2006. Azimuthal variations in polarimetric microwave measurements observed over Dome C, Antarctica. In: The Microwave Remote Sensing of the Atmosphere and Environment, Society of Photo-Optical and Instrumentation Engineers Proceedings. http://dx.doi.org/10.117/12.693503. Interpretive Summary:
Technical Abstract: WindSat is the first spaceborne fully polarimetric radiometer. It observes all four components Tv (vertically polarized), Th (horizontally), U (difference between polarizations at +45° and -45°) and V (difference right hand minus left hand circular polarized) of the Stokes vector. While originally developed to retrieve wind speed and direction over ocean, here we investigate the signals observed over Dome C, Antarctica, at about 3200 m asl with nearly flat terrain. The seasonal cycles of Tv and Th reflect the surface temperature cycle and the penetration depth decreasing with increasing frequency (6 to 37 GHz), while the difference Tv – Th is nearly constant. The U and V signals are most pronounced in Austral winter (July-August). The differences between ascending and descending overpasses, corresponding to different azimuth observing directions, take values up to 1.2 K (U) and 3 K (V). Fitting the data of for and aft swath to a second order harmonic function of the azimuth angle reveals a consistent orientation of the structures at the used frequencies 10 and 37 GHz and Stokes components U and V in the direction of about 153° E, consistent with the small overall slope direction of the terrain (145°) and ERS scatterometer observations. The WindSat measured Tv and Th are analysed with AWS measured temperature to verify the temperature dependency of these channels over Dome C. The paper provides the initial results of our ongoing studies over the entire Antarctica ice sheet that will aid in analyses of other landforms.