Development of a Polarimetric 50-GHz Spectrometer for Temperature Sounding in the Middle Atmosphere

This article addresses the further development of the ground-based temperature radiometer TEMPERA, which measures atmospheric microwave radiation in one linear polarization in order to retrieve temperature profiles up to an altitude of 50 km (Stahli et al., 2013). The latest innovation is a new polarimetric receiver, which allows observing the atmosphere simultaneously in left- and right-circular polarization. In combination with an adapted inversion method, the fully polarimetric analysis can improve the accuracy and extends the vertical upper limit of retrieved temperature profiles. Comparisons between single polarization and fully polarimetric retrievals with simulated atmospheric spectra are presented, and the influence of the Earth's magnetic field is analyzed. In addition, we propose a simple calibration method for fully polarimetric radiometers and present first atmospheric spectra measured with the new TEMPERA-C instrument.