The main objective of this project is a complete spectral characterization of cirrus and mixed phase clouds in order to evaluate the radiative models in the FIR regime, where the clouds effect is very strong, and systematic spectral measurements are scarcely available. The required spectral radiance measurements in the range 100-1000 cm-1 are acquired by the Fourier spectroradiometer REFIR-PAD, which is operative in continuous and unattended mode at Dome-C, whereas the atmospheric cloud fields are constrained with the support of a backscattering/depolarization lidar, for the estimation of the clouds position, phase, and the extinction profile, an ice and halo imager cameras, for the assessment of the cloud ice crystals micro-physics, and a micro rain radar (MRR) for the determination of the clouds reflectivity and the vertical velocity of ice crystals in the cases of precipitating clouds.