Remote sensing of polar ice and mixed phase clouds properties by means of far infrared spectral measurements over the Antarctic Plateau

The relevant role of cirrus clouds in the Earth's radiation budget is proven but it is still uncertain. The uncertain in the estimate of the radiative impact is due to the high variability in the size/shape distribution of ice particles. This effect is very strong in the atmospheric window between 820-960 cm -1 (8-12 ?m) but the contribution in the far infrared (FIR) of the spectrum, below 667 cm -1 (> 15 ?m), is also very important as well. This work describes the retrieval techniques to invert remote sensing data of the ice clouds to obtain their optical and micro-physical properties, such as the crystals effective diameter, the ice water path and optical depth. The retrieval has been performed by using the Simultaneous Atmospheric and Clouds Retrieval (SACR) code, which is based on the optimal estimation approach. The algorithm allows the simultaneous retrieval of the atmospheric variables, such as the vertical profiles of water vapour and temperature, and the cirrus clouds properties by using the single scattering coefficients of different ice crystal habits tabulated in specific databases. The retrieval procedure has been applied to both ground-based and space applications in support to the Far-infrared-Outgoing- Radiation Understanding and Monitoring (FORUM) ESA mission