DOI: 10.4121/9034ff3f-047a-4c46-9939-491b2edee5be.v1
title: TU Delft Cloud radar data - CLARA 35 GHz Slant Profiles

description: <strong>Description:</strong>Slant profiles of clouds and precipitation measured by dual-frequency cloud radar: dual-frequency (35 and 94 GHz) polarimetry and spectral polarimetry of precipitation, ice, and mixed-phase clouds.<br>This dataset at 35 GHz contains slant profiles of clouds and precipitation observed using a dual-frequency, dual-polarization, frequency-modulated continuous-wave (FMCW) cloud radar located at the atmospheric site Cabauw. The radar, developed by Radiometer Physics GmbH (RPG-FMCW-DP-KW type) and named CLoud Atmospheric RAdar (CLARA), operates at 35 GHz and 94 GHz. CLARA is situated on a 1-meter-high platform. It employs simultaneous transmission and simultaneous reception (STSR) mode. There is a rain/snow/fog mitigation system, comprising a dew blower and a heater which prevent the accumulation of liquid drops and ice on the hydrophobic antenna radomes, therefore mitigating attenuation caused by the presence of liquid water on the antennas.<br>Measurements are collected at a fixed elevation angle (default: 45°) and constant azimuth. The dual-frequency observations are synchronized in viewing direction, sampling time, and range resolution, but differ in beamwidth—0.84° at 35 GHz and 0.56° at 94 GHz—as well as in maximum unambiguous Doppler velocity.<br>CLARA includes embedded passive channels at 31 GHz and 89 GHz, enabling Liquid Water Path (LWP) retrievals using the same receiving antenna. Additionally, it is coupled with a HATPRO G5 microwave radiometer (CLARIO), providing collocated radiometric measurements at the same temporal resolution. A built-in weather station (Vaisala WXT536) also records ground-level meteorological conditions.<br>In terms of calibration, the transmit power is continuously monitored, and the radar receiver (including the receiving antenna) undergoes calibration every six months using clear sky calibration. Short-term calibration is provided through periodic Dicke switching. Prior to the semiannual calibration procedure, the hydrophobic antenna radomes are replaced.<br>This dataset is part of a broader collection from the Department of Geoscience and Remote Sensing (GRS) at TU Delft, published within the Ruisdael Observatory framework (https://ruisdael-observatory.nl/). This dataset will continue to be updated over time while the cloud radar remains operational.<br><strong>List of variables:</strong>* sensor and site parameters* measurement specifications* processing specifications* weather station measurements* LWP in the looking direction of the cloud radar * profiles of temperature, absolute and relative humidity (CLARIO)* Doppler spectra (HH and VV) and covariance spectrum (LV0 files)* Equivalent reflectivity factor (LV1 files)* Doppler variables (LV1 files)* Polarimetric variables (LV1 files)<br><strong>Relevance:</strong>The dataset "Dual-frequency (35 and 94 GHz) polarimetry and spectral polarimetry of precipitation, ice, and mixed-phase clouds" is highly valuable for advancing our understanding of cloud and precipitation microphysics. By combining measurements at both Ka-band (35 GHz) and W-band (94 GHz), the datasets (35 and 94 GHz) provide enhanced sensitivity to a wide range of particle sizes and phases, enabling more accurate retrievals of hydrometeor properties such as size, shape, density, and phase composition. The inclusion of polarimetric and spectral information allows for detailed analysis of scattering and dynamical processes, including aggregation, riming, and turbulence effects. This dataset is particularly relevant for validating satellite observations, refining dual-frequency radar retrieval algorithms, and improving the representation of cloud and precipitation processes in weather and climate models.