Spanish Meteorological Agency

Madrid, Spain

Spanish Meteorological Agency

Madrid, Spain
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Gallardo-Hernando B.,Technical University of Madrid | Perez-Martinez F.,Technical University of Madrid | Munoz-Ferreras J.M.,University of Alcalá | Aguado-Encabo F.,Spanish Meteorological Agency
IEEE National Radar Conference - Proceedings | Year: 2010

The use of wind turbines to generate electricity has become a major problem in meteorological radars. Due to the low frequency resolution that these radars show, the most representative wind turbine radar signature characteristics can't be observed in operational exploration modes by using the classical Fourier spectral estimation. In this paper, we propose super-resolution techniques to improve Fourier's Doppler resolution and provide experimental results. © 2010 IEEE.

Gallardo-Hernando B.,Technical University of Madrid | Gallardo-Hernando B.,Spanish Meteorological Agency | Munoz-Ferreras J.M.,University of Alcalá | Perez-Martinez F.,Technical University of Madrid | Aguado-Encabo F.,Spanish Meteorological Agency
IET Radar, Sonar and Navigation | Year: 2011

The use of wind energy is gaining importance because of its many advantages. Nations worldwide are promoting the installation of wind farms to produce electricity in an attempt to tackle climate change and increasing oil costs. However, wind turbines can generate undesired signals that disturb the performance of radar systems. In particular, this is an issue for weather radar networks that see wind turbines as clutter, since they have a strong influence on meteorological outputs such as the estimation of rain intensity or wind velocity. This study develops a simulated scenario and a radar signal model that justify collection of live data from the Spanish Weather Radar Network. Simulated and real data are discussed for both the spotlight and exploration modes. As an application example, a simple algorithm has been developed to estimate wind direction in the immediate vicinity of wind turbines. In this context, it is clear that some meteorological information may be extracted from the wind turbine clutter itself. © 2011 © The Institution of Engineering and Technology.

Gallardo-Hernando B.,Technical University of Madrid | Gallardo-Hernando B.,Spanish Meteorological Agency | Perez-Martinez F.,Technical University of Madrid | Aguado-Encabo F.,Spanish Meteorological Agency
IET Radar, Sonar and Navigation | Year: 2010

Wind farm installations that are near radar systems cause clutter returns that can affect the normal operation of the radar. Wind turbines provoke clutter reflectivity returns with unpredictable Doppler spreads that are not easily minimised. In this study, the authors focus on the mitigation of wind turbine clutter (WTC) for C-band weather radar. The proposed detection technique is applicable when using the spotlight operation mode during radar data gathering. This means that the dwell time must be long enough to observe certain statistics that allow for the detection of wind turbines. This specific operation mode can be used between normal radar scans. The detection technique can be applied before or after real rain data are added to WTC, with different results. Our mitigation technique uses the information from bins adjacent to WTC detections. The authors test this algorithm with real data from wind farms in rainy weather. The results are encouraging, because the absolute errors, both in reflectivity and in velocity measurements, are significantly reduced. © 2010 The Institution of Engineering and Technology.

Torres B.,University of Valladolid | Torres B.,Lille University of Science and Technology | Dubovik O.,Lille University of Science and Technology | Toledano C.,University of Valladolid | And 5 more authors.
Atmospheric Chemistry and Physics | Year: 2014

A sensitivity study of aerosol retrievals to the geometrical configuration of the ground-based sky radiometer observations is carried out through inversion tests. Specifically, this study is focused on principal plane and almucantar observations, since these geometries are employed in AERONET (AErosol RObotic NETwork). The following effects have been analyzed with simulated data for both geometries: sensitivity of the retrieval to variability of the observed scattering angle range, uncertainties in the assumptions of the aerosol vertical distribution, surface reflectance, possible instrument pointing errors, and the effects of the finite field of view. The synthetic observations of radiometer in the tests were calculated using a previous climatology data set of retrieved aerosol properties over three AERONET sites: Mongu (Zambia) for biomass burning aerosol, Goddard Space Flight Center (GSFC; Maryland, USA) for urban aerosol and Solar Village (Saudi Arabia) for desert dust aerosol. The results show that almucantar retrievals, in general, are more reliable than principal plane retrievals in presence of the analyzed error sources. This fact partially can be explained by practical advantages of the almucantar geometry: the symmetry between its left and right branches that helps to eliminate some observational uncertainties and the constant value of optical mass during the measurements, that make almucantar observations nearly independent of the vertical variability of aerosol. Nevertheless, almucantar retrievals present instabilities at high sun elevations due to the reduction of the scattering angle range coverage, resulting in decrease of information content. It is in such conditions that principal plane retrievals show a better stability, as shown by the simulation analysis of the three different aerosol models. The last part of the study is devoted to the identification of possible differences between the aerosol retrieval results obtained from real AERONET data using both geometries. In particular, we have compared AERONET retrievals at the same sites used in the simulation analysis: Mongu (biomass burning), GSFC (urban) and Solar Village (desert dust). Overall, this analysis shows robust consistency between the retrievals from simultaneous observations in principle plane and almucantar All identified differences are within the uncertainties estimated for the AERONET operational aerosol retrieval. The differences in the size distribution are generally under 10% for radii between 0.1 μm and 5 μm, and outside this size range, the differences can be as large as 50%. For the absorption parameters, i.e., single scattering albedo and the imaginary part of the refractive index, the differences are typically under 0.01 and 0.003, respectively. The real part of the refractive index showed a difference of 0.01 for biomass burning and urban aerosol, and a difference of around 0.03 for desert dust. Finally, it should be noted that the whole data set includes only 200 pairs, which have been taken under very stable atmospheric conditions; therefore, in a general case, differences between principal plane (PPL) and almucantar (ALM) are expected to be higher. Though the observed differences between ALM and PPL are rather small, it should be noted that this analysis has been conducted using a limited set of 200 observation pairs selected under stable atmospheric conditions. © Author(s) 2014.

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