Thomas Rose

Microwave Radiometer for Cloud Carthography: A 22-channel ground-based microwave radiometer for atmospheric research

A 22-channel Microwave Radiometer for Cloud Carthography (MICCY) for the profiling of tropospheric temperature, humidity, and cloud liquid water has been developed. The radiometer has 10 channels along the high-frequency wing of the 22.235 GHz water vapor line, 10 channels along the low-frequency side of the 60 GHz oxygen complex, and 2 channels at 90 GHz. Two features make the radiometer a unique tool for the observation of small-scale structures related to cloud processes: (1) Atmospheric brightness temperatures are measured simultaneously at all channels with an integration time of 1 s. (2) A Cassegrain system including a 90 cm off-axis parabolic mirror leads to a spatial resolution better than 1° full width at half maximum for all frequencies. The necessity of these features for cloud observations is demonstrated. Algorithms for the retrieval of integrated water vapor, integrated cloud liquid water, and the profiles of temperature and humidity were developed on the basis of artificial neural networks. Measurement examples, including comparisons with radiosondes, demonstrate the systems capabilities for high-resolution atmospheric monitoring.

Characterization of Precipitating Clouds by Ground-Based Measurements with the Triple-Frequency Polarized Microwave Radiometer ADMIRARI

Abstract A groundbreaking new-concept multiwavelength dual-polarized Advanced Microwave Radiometer for Rain Identification (ADMIRARI) has been built and continuously operated in two field campaigns: the Convective and Orographically Induced Precipitation Study (COPS) and the European Integrated Project on Aerosol Cloud Climate Air Quality Interactions (EUCAARI). The radiometer has 6 channels working in horizontal and vertical polarization at 10.65, 21.0, and 36.5 GHz, and it is completely steerable both in azimuth and in elevation. The instrument is suited to be operated in rainy conditions and is intended for retrieving simultaneously water vapor, rain, and cloud liquid water paths. To this goal the authors implemented a Bayesian retrieval scheme based on many state realizations simulated by the Goddard Cumulus Ensemble model that build up a prior probability density function of rainfall profiles. Detailed three-dimensional radiative transfer calculations, which account for the presence of nonspherical p...

Rain Observations by a Multifrequency Dual-Polarized Radiometer

During the Convective and Orographically Induced Precipitation Study, advanced microwave radiometer for rain identification has continuously acquired measurements at the Atmospheric Radiation Measurement Mobile Facility in the Black Forest from the beginning of August until December 2007. The radiometer has six channels measuring in horizontal and vertical polarizations at 10.65, 21.0, and 36.5 GHz. Rainy events have been selected out of the entire database according to collocated gauges and, subsequently, analyzed. Measured brightness temperatures and (vertical-horizontal) polarization differences are interpreted by comparing with radiative transfer simulations, which account for the presence of nonspherical particles in preferential orientation. Measurements confirm the importance of the polarization signal for separating the effect introduced by non-Rayleigh scatterers and, therefore, the rain from the cloud component. More quantitative interpretation of the signal requires a better understanding of the role played by melting particles and an identification of the 3-D structure of the precipitating system under observation. Both aspects will be tackled in the near future by exploiting the synergy with a coinstalled micro rain radar.

A water vapour monitor at Paranal Observatory

We present the performance characteristics of a water vapour monitor that has been permanently deployed at ESO’s Paranal observatory as a part of the VISIR upgrade project. After a careful analysis of the requirements and an open call for tender, the Low Humidity and Temperature Profiling microwave radiometer (LHATPRO), manufactured by Radiometer Physics GmbH (RPG), has been selected. The unit measures several channels across the strong water vapour emission line at 183 GHz, necessary for resolving the low levels of precipitable water vapour (PWV) that are prevalent on Paranal (median ~2.5 mm). The unit comprises the above humidity profiler (183-191 GHz), a temperature profiler (51-58 GHz), and an infrared radiometer (~10 μm) for cloud detection. The instrument has been commissioned during a 2.5 week period in Oct/Nov 2011, by comparing its measurements of PWV and atmospheric profiles with the ones obtained by 22 radiosonde balloons. In parallel an IR radiometer (Univ. Lethbridge) has been operated, and various observations with ESO facility spectrographs have been taken. The RPG radiometer has been validated across the range 0.5 – 9 mm demonstrating an accuracy of better than 0.1 mm. The saturation limit of the radiometer is about 20 mm. Currently, the radiometer is being integrated into the Paranal infrastructure to serve as a high time-resolution monitor in support of VLT science operations. The water vapour radiometer’s ability to provide high precision, high time resolution information on this important aspect of the atmosphere will be most useful for conducting IR observations with the VLT under optimal conditions.

Submillimetre-wave receiver developments for ICI onboard MetOP-SG and ice cloud remote sensing instruments

The development of heterodyne receiver channels at frequencies ranging from 183 GHz up to 664 GHz, and compatible with the requirements of both the ICI instrument onboard MetOp-SG and the ISMAR instrument onboard the FAAM aircraft are presented. In order to optimize the performance VS cost factor, multi-channels architecture that enhances commonalities as well as maximum redundancies in the use of planar Schottky diode is adopted. The performance of each component is close if not at the state-of-the-art. For these receivers, broadband high power and high efficiency mutlipliers, and also high sensitivity subharmonic mixers are required. These developments are also possible thanks to the availability of novel test equipment systems such as VNA and Spectrum Analyser extenders up to 750 GHz in order to characterize fully each component. Performance of these submillimetre wave test equipment systems developed by RPG is also presented.

A Novel Ground-Based Microwave Radiometer for High Precision Atmospheric Observations between 10 and 90 GHz

State-of-the-art microwave radiometers for probing water vapor, temperature and cloud liquid water do not show the high accuracy and stability which is needed for some applications like radio science or the assessment of turbulent weather conditions. Especially scientific experiments, performed in outer-space and missions to investigate other planets, are dependent upon high-precision transmission of data to receivers on Earth passing through the atmosphere, which is a big source of disturbance. Propagation and attenuation at frequencies between a few GHz and several tens of GHz are influenced by dry air as well as by water vapour and liquid water in form of clouds and rain. A precise and stable microwave radiometer to derive these properties has been developed - the Atmospheric Propagation and Profiling System ATPROP.

A W-Band Radar–Radiometer System for Accurate and Continuous Monitoring of Clouds and Precipitation

AbstractA new 94-GHz frequency-modulated continuous wave (FMCW) Doppler radar–radiometer system [Julich Observatory for Cloud Evolution (JOYCE) Radar–94 GHz (JOYRAD-94)] is presented that is suitable for long-term continuous observations of cloud and precipitation processes. New features of the system include an optimally beam-matched radar–radiometer; a vertical resolution of up to 5 m with sensitivities down to −62 dBZ at 100-m distance; adjustable measurement configurations within the vertical column to account for different observational requirements; an automatic regulation of the transmitter power to avoid receiver saturation; and a high-powered blowing system that prevents hydrometeors from adhering to the radome. JOYRAD-94 has been calibrated with an uncertainty of 0.5 dB that was assessed by observing a metal sphere in the radar’s far field and by comparing radar reflectivities to a collocated 35-GHz radar. The calibrations of the radar receiver and the radiometric receiver are performed via a tw...

AWARDS: Advanced microwave radiometers for deep space stations

The objective of this study, named AWARDS Advanced microWAve Radiometers in Deep space Stations, is the preliminary design of a transmission Media Calibration System MCS to be located at an ESA Deep Space Antenna DSA site. The crucial aspect is the capability to accurately retrieve the tropospheric path delay along the line-of-sight of the deep space probe in order to allow precise tropospheric calibration of deep space observables range and range-rate with particular reference to the BepiColombo spacecraft and its primary DSA at Cebreros ES. The study focuses on two main aspects which lead to the preliminary design of the Mercury Orbiter Radioscience Experiment MORE MCS: the characterization of current microwave radiometers MWRs available at ESA/ESTEC and the atmospheric fluctuation effects on the MCS error budget, in terms of the Allan standard deviation ASD. In the course of the study, further critical aspects have been identified effects of Sun contamination, effects of ground noise emission, and mitigation strategies have been proposed. The final outcome is a preliminary design of the MWR and the entire MCS to be deployed at the ESA/ESTRACK ESA Tracking station network sites and being compliant with MORE requirements.