Consistency Test of Precipitating Ice Cloud Retrieval Properties Obtained From The Observations of Different Instruments Operating at Dome-c (antarctica)

Abstract

Selected case studies of precipitating ice clouds at Dome-C (Antarctic Plateau) are used to test a new approach for the estimation of ice cloud reflectivity at 24 GHz (12.37 mm of wavelength) using ground-based far infrared spectral measurements from the REFIR-PAD Fourier transform spectroradiometer and backscattering/depolarization lidar profiles. The resulting reflectivity is evaluated with the direct reflectivity measurements provided by a co-located micro rain radar (MRR) operating at 24 GHz, which is able to detect falling crystals with large particle size, typically above 500 μm. To obtain the 24 GHz reflectivity, we used the particle effective diameter and the cloud optical depth retrieved from the far infrared spectral radiances provided by REFIR-PAD and the tropospheric co-located backscattering lidar to calculate the modal radius and the intercept of the particle size distribution. From these, the theoretical reflectivity at 24 GHz is obtained by integrating the size distribution over different microwave cross sections for various habit crystals provided by Eriksson et al. (2018) databases. From the comparison with the radar reflectivity measurements, we found that the column-like habits and the plates/columnar crystal aggregates show the best agreement with the MRR observations. The presence of (hexagonal) columns is confirmed both by the presence of 22° solar halos, detected by the HALO-CAMERA, and by the crystal images taken by the ICE-CAMERA, operating in proximity of REFIR-PAD and the MRR. The average crystal lengths obtained from the retrieved size distribution are also compared to the ones estimated from the ICE-CAMERA images. The agreement between the two results confirms that the retrieved parameters of the particle size distributions correctly reproduce the observations.