Modelling of weather radar echoes from anomalous propagation using a hybrid parabolic equation method and NWP model data

Contamination of weather radar echoes by anomalous propagation (anaprop) mechanisms remains a serious issue in quality control of radar precipitation estimates. Although significant progress has been made identifying clutter due to anaprop there is no unique method that solves the question of data reliability without removing genuine data. The work described here relates to the development of a software application that uses a numerical weather prediction (NWP) model to obtain the temperature, humidity and pressure fields to calculate the three dimensional structure of the atmospheric refractive index structure, from which a physically based prediction of the incidence of clutter can be made. This technique can be used in conjunction with existing methods for clutter removal by modifying parameters of detectors or filters according to the physical evidence for anomalous propagation conditions. The parabolic equation method (PEM) is a well established technique for solving the equations for beam propagation in a non-uniformly stratified atmosphere, but although intrinsically very efficient, is not sufficiently fast to be practicable for near real-time modelling of clutter over the entire area observed by a typical weather radar. We demonstrate a fast hybrid PEM technique that is capable of providing acceptable results in conjunction with a high-resolution terrain elevation model, using a standard desktop personal computer. We discuss the performance of the method and approaches for the improvement of the model profiles in the lowest levels of the troposphere

Modelling of weather radar echoes from anomalous propagation using a hybrid parabolic equation method and NWP model data

Contamination of weather radar echoes by anomalous propagation (anaprop) mechanisms remains a serious issue in quality control of radar precipitation estimates. Although significant progress has been made identifying clutter due to anaprop there is no unique method that solves the question of data reliability without removing genuine data. The work described here relates to the development of a software application that uses a numerical weather prediction (NWP) model to obtain the temperature, humidity and pressure fields to calculate the three dimensional structure of the atmospheric refractive index structure, from which a physically based prediction of the incidence of clutter can be made. This technique can be used in conjunction with existing methods for clutter removal by modifying parameters of detectors or filters according to the physical evidence for anomalous propagation conditions. The parabolic equation method (PEM) is a well established technique for solving the equations for beam propagation in a non-uniformly stratified atmosphere, but although intrinsically very efficient, is not sufficiently fast to be practicable for near real-time modelling of clutter over the entire area observed by a typical weather radar. We demonstrate a fast hybrid PEM technique that is capable of providing acceptable results in conjunction with a high-resolution terrain elevation model, using a standard desktop personal computer. We discuss the performance of the method and approaches for the improvement of the model profiles in the lowest levels of the troposphere

A Novel Look into Digital Beamforming Techniques for Multipath and Interference Mitigation in Galileo Ground Stations

In this paper, we explore the adoption of Array Signal Processing in Galileo Ground Stations. The main motivation comes from the need of efficiently mitigating multipath and interference sources in order to achieve centimetre accuracy. One of the critical aspects appearing when an array of antennas is implemented resides on the array perturbations and mismodelling. For that reason, this work places special emphasis on this issue and some robust beamforming techniques are proposed. Differently from other studies addressing the use of conventional beamforming techniques for navigation applications, we propose novel strategies specially adapted to the considered scenario. As shown in the paper, the use of digital beamforming allows for a (at least) 47% reduction in terms of tracking errors when compared to a single antenna receiver

ADIBEAM: Adaptive Digital Beamforming for Galileo Reference Ground Stations

Navigation accuracy and integrity demanded by Galileo and its future evolution motivate the study and design of advance receiving techniques. In that direction, the ADIBEAM project focus on the design of high accuracy ground stations. More specifically, the project deals with the adoption of advance receivers based on the use of arrays of antennas and digital beamforming. In this paper, we present the receiver solution proposed in the project. This solution has been designed aimed at addressing the problems arising when an array of antennas is implemented in practice. Basically, the main problem is the extreme difficult to perfectly control and calibrates all the components of the system. For that reason, a realistic Experimentation Platform has been developed. This platform is based on the software emulation of all the components of the system and the implementation of a GNSS software receiver based on digital beamforming. Concerning the beamforming solutions, robust approaches have been proposed in order to cope with array perturbations. As revealed by the results obtained in the project, the proposed receiver architecture based on the adoption of an antenna array is able to attain code centimetre and carrier millimetre accuracy in challenging scenarios with multipath, interference and scintillation effects