The main goal of the project is the identification of well-characterized case studies aimed at a radiative self-consistency experiment of ice clouds and in mixed phase on the Antarctic Plateau, as well as the improvement of current spectral patterns in the far-infrared region. This can be achieved through the synergistic use of various measurement instruments operating in different bands of the electromagnetic spectrum and installed at the Concordia base, particularly at the Physics shelter. The infrared radiation emitted by the atmosphere and clouds is measured by the Fourier transform spectroradiometer REFIR-PAD (Radiation Explorer in Far Infrared - Prototype for Applications and Development) operating at Concordia since 2012 inside the DoCTOR PNRA project by Dr. Giovanni Bianchini (https://www.pnra.aq/it/project/330/dome-c-tropospheric-observer-osservatorio-troposferico-dome-c). The position and phase of clouds is estimated by the backscattering and depolarization LIDAR active since 2008. The particle size distribution can be estimated by an ICE- CAMERA, i.e., a kind of optical scanner that collects precipitating ice crystals on the shelter roof. As of the 2018-2019 campaign, a 24 GHz weather radar (Micro Rain Radar, MMR) operating continuously has been installed on the roof of Physics, which can provide an estimate of the precipitation rate of ice crystals and the falling velocities of those crystals. From these measurements, efforts are also being made to estimate the ice content in the case of precipitating ice clouds. Finally, during the last 2019-2020 campaign, a HALO-CAMERA was also installed, which can provide an estimate of the shape of ice crystals that can be used as a priori information in transfer models radiative suitable for simulating the effect of clouds. In order to complete the radiative closure (or self-consistency) experiment, the idea is to use the values of the parameters of the precipitating ice clouds, i.e., optical thickness and effective diameter, obtained from the inversion of the spectra produced by REFIR-PAD, to characterize the size distribution of the ice crystals and use the latter to calculate the reflectivity at the MRR radar wavelength, i.e., 24 GHz. The calculation of reflectivity obviously depends on the type of particles (habit) that are assumed, so the inversion procedure of the spectra produced by REFIR-PAD is repeated assuming different types of particles, thus using different optical property databases depending on whether aggregates, bullet rosettes, hexagonal columns, platelets or hollow columns are used. Consequently, the same habit assumptions will have to be made for the calculation of radar reflectivity. The reflectivity obtained can at this point be compared with the experimental reflectivity measured by MRR. Data analysis was carried out by Dr. Alessandro Bracci of ISAC-CNR and Giacomo Roversi of Ca' Foscari University of Venice, both belonging to the group led by Dr. Luca Baldini. Unfortunately, the very small size of the crystals at Concordia, due to the extremely low temperatures and very low humidity values, make it difficult to detect many of these crystals. For this reason, an initial work involved precisely the selection of optimal cases that could be analyzed. The work appears to be still in progress although positive results have already been obtained from the retrieval products of REFIR-PAD, which have allowed the estimation of the reflectivity at 24 GHz, which has been compared ,in the cases of best radar signal, with that measured by MRR obtaining a good agreement. The backscattering signal allows to derive the top and bottom elevations of the cloud to be fixed in the simulation of the radiative transfer. The depolarization signal makes it possible to discriminate the presence of ice, as water droplets do not produce depolarization signal. The lidar data, along with halo-camera and ice-camera data, are provided by Dr. Massimo Del Guasta.

The knowledge of properties and quantitative measurement of solid precipitation in Antarctica is of fundamental importance as precipitation represents the main input of Antarctic ice sheet mass, the variations of which have a direct and non-negligible effect on the average level of the oceans at global scale. Characterization and quantification of the precipitation is crucial in defining and validating global climate models and numerical weather prediction models, as well as anchoring and validating space-borne remote sensing estimates from missions like CloudSAT and EarthCARE. A snow and cloud microphysics observatory has been set up at the Italian Antarctic station Mario Zucchelli (MZS), integrating the pre-existing instrumentation for weather measurements. In particular, a 24-GHz vertical pointing Doppler radar, the METEK's Micro Rain Radar 2 (MRR-2), and a laser disdrometer, the OTT Parsivel, have been integrated with the advanced weather stations, radiosoundings and the ceilometer already present at MZS. The synergy between the set of instruments allows for characterizing precipitation and studying properties of Antarctic precipitation such as dimension, shape, fall behavior, particle number density, particles size distribution, particles terminal velocity, reflectivity factor and information on their vertical extent. APP started as a four-year project in July 2017, covering the Special Observation Period (SOP) in the Southern Hemisphere of Year of Polar Predicition (YOPP) period. APP can provide specific measurements for precipitation occurring over the Antarctic coast at high temporal resolution, in particular specific snow products such as snow rate, snow depth and their water equivalent. In November 2023 the observatory received an additional instrument, the Thies Clima 3D Stereo imaging disdrometer, which was previously installed for one year in Italy for testing, at the Casale Calore (AQ) meteorological observation site from the University of L'Aquila. The research team of the first two years was coordinated by Nicoletta Roberto, with operational units at the Rome unit of the CNR-ISAC (Luca Baldini, Elisa Adirosi, Stefano Dietrich) and at the Department of Physics and Astronomy of the University of Bologna (Rolando Rizzi, Federico Porcù, Tiziano Maestri, Alessandro Bracci). From 2020 the coordination of the project passed to Luca Baldini (CNR-ISAC) and the work team was extended with the research fellows Giacomo Roversi and Sabina Angeloni.

Vertical profiles along the first kilometre of atmosphere above the ground (from 105 to 1050 m a.g.l.) of equivalent radar reflectivity factor (Ze), Doppler velocity (W) and Doppler spectral width (Sw) from a 24-GHz vertically pointing Micro Rain Radar MRR-2 by METEK GmbH positioned at Mario Zucchelli Station (Antarctica).

Disdrometric data from an OTT Parsivel with 32 size classes and 32 velocity classes positioned at Mario Zucchelli Station (Antarctica), with monthly spectra and particle size distributions (PSD).

Vertical profiles along the first three kilometres of atmosphere above the ground (from 300 to 3000 m a.g.l.) of equivalent radar reflectivity factor (Ze), Doppler velocity (W) and Doppler spectral width (Sw) from a 24-GHz vertically pointing Micro Rain Radar MRR-2 by METEK GmbH positioned at Concordia Station (Dome C, Antarctica). The main objective of the FIRCLOUDS 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 micro rain radar (MRR) data allows the determination of the clouds reflectivity and the vertical velocity of ice crystals in the cases of precipitating clouds.

Backscattering and depolarization data from a LIDAR positioned at Concordia Station (Dome C, Antarctica). Data are available on the INO-CNR server on request to Dr. Massimo Del Guasta. The main objective of the FIRCLOUDS projectis 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. A backscattering/depolarization lidar contributes to the estimation of the clouds position and phase, and of the optical extinction profile.

Pictures of the ice camera and the halo camera positioned at Concordia Station (Dome C, Antarctica). Data are available on the INO-CNR server on request to Dr. Massimo Del Guasta. The main objective of the FIRCLOUDS 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 ice and halo imager cameras enable an assessment of the cloud ice crystals micro-physics.

Disdrometric data from a Thies Clima 3D Stereo with 22 size classes and 20 velocity classes positioned at L'Aquila (Italy, 42.3831 N, 13.3148 E, 683 m a.s.l.), with monthly spectra and ancillary information.