Tomeu Rigo

Quality Control of Antenna Alignment and Receiver Calibration Using the Sun: Adaptation to Midrange Weather Radar Observations at Low Elevation Angles

A quality control method for combined online monitoring of weather radar antenna pointing biases and receivercalibrationusingsolarsignalsdetectedbyanoperationalradarisadaptedforapplicationtomidrange radar data (80‐150km). As the original method was developed using long-range data, additional criteria based on robust statistical estimators are imposed in the sun signature detection and selection process, allowing to discard observations biased by ground clutter or precipitation and to remove very influential outliers. The validity ranges of the physical model describing the solar interferences detected by the scanning radar antenna are explicitly defined and an equation for estimation of the effective scanning width in reception is provided in a thorough theoretical derivation. The method proposed reveals its sensitivity to changes in the antenna pointing accuracy and receiver calibration when applied to operational data obtained with three C-band radars during one year. A comparative study on the goodness of fit between a three- and a five-parameter model highlights the effect on the stability and accuracy of the antenna and receiver parameters retrieved for each radar system, considering the dissimilar information content of the observations collected by each radar. The performance of the proposed methodology under the effects of the presence of ground clutter and radio local area network interferences is discussed in the results presented.

Correction of Dual-PRF Doppler Velocity Outliers in the Presence of Aliasing

AbstractIn Doppler weather radars, the presence of unfolding errors or outliers is a well-known quality issue for radial velocity fields estimated using the dual–pulse repetition frequency (PRF) technique. Postprocessing methods have been developed to correct dual-PRF outliers, but these need prior application of a dealiasing algorithm for an adequate correction. This paper presents an alternative procedure based on circular statistics that corrects dual-PRF errors in the presence of extended Nyquist aliasing. The correction potential of the proposed method is quantitatively tested by means of velocity field simulations and is exemplified in the application to real cases, including severe storm events. The comparison with two other existing correction methods indicates an improved performance in the correction of clustered outliers. The technique proposed is well suited for real-time applications requiring high-quality Doppler radar velocity fields, such as wind shear and mesocyclone detection algorithms,...

Intercomparison and Potential Synergies of Three Methods for Weather Radar Antenna Pointing Assessment

AbstractThree methods for estimation of the weather radar antenna azimuth and elevation pointing offsets are compared. Two of the methods reviewed use the known location of the sun as a reference. The first of these methods is based on an offline scan of the sun disk. The second method detects and characterizes solar interferences in operative scans. The third method consists of correlating measured ground clutter echoes with echoes simulated using a high-resolution digital elevation model. The main objectives are to review the characteristics in each case, studying their performance in actual operative conditions, and to examine the reasons for the discrepancies between the reported pointing bias estimates, with the aim of laying the groundwork for an optimized individual or combined application and interpretation of the methods. Daily pointing biases estimated through the sun-scanning procedure in a dedicated one-month, short-term campaign are the base for the intercomparison. When applied to the three ...

6 – Techniques and Instruments to Aid in the Monitoring of Flood Events

Abstract: One of the main problems when monitoring and analyzing flood events is the instrumentation required to gather quantitative observations. Flash floods are usually produced in ungauged catchments or non-permanent water streams. In these conditions, the only solutions are to estimate the magnitude of the event based on the impact, the water level, the precipitation or the hydrological or hydraulic modeling. In other occasions, the river gauge stations can be destroyed and carried away by the own flood. In these situations, having good access to precipitation measurements appears to be the better solution, not only because they are the primary source of information to describe the event but also because they can provide the main input for the hydrological modeling.