Browsing by Author "Maruri, Mercedes"
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Item A case of winter lightning initiation from a tall structure in the Basque Country(Institute of Electrical and Electronics Engineers Inc., 2017-02-07) Lopez, Javier; Montanya, Joan; Maruri, Mercedes; Aranda, Jose Antonio; Gaztelumendi, Santiago; Centros PRE-FUSION TECNALIA - (FORMER); WEATHER AND CLIMATE INTELLIGENCE FOR BUSINESSLightning research is usually focused on the most active months of the year, those corresponding to the summer season. These thunderstorms produce most of the lightning records during a year in the Basque Country, and they are recorded for further research. In this paper winter lightning is under study. After the dramatic descent in the number of strokes recorded with the end of the summer season, a number of winter thunderstorms crossed the territory. Two different episodes (one in November 7th and 8th 2009, and a thunderstorm in November 30th 2009) left evidence of lightning in the weather radar tower located at Kapildui Mountain. In this paper the research carried out from the first evidence of electrical activity in the tower to the final conclusions of being upward negative flashes initiated by the tower is presented.Item Cross-calibration of different radar systems for monitoring nocturnal bird migration across Europe and the Near East(2019-05) Liechti, Felix; Aschwanden, Janine; Blew, Jan; Boos, Mathieu; Brabant, Robin; Dokter, Adriaan M.; Kosarev, Vladislav; Lukach, Maryna; Maruri, Mercedes; Reyniers, Maarten; Schekler, Inbal; Schmaljohann, Heiko; Schmid, Baptiste; Weisshaupt, Nadja; Sapir, Nir; WEATHER AND CLIMATE INTELLIGENCE FOR BUSINESSLarge parts of the continents are continuously scanned by terrestrial weather radars to monitor precipitation and wind conditions. These systems also monitor the mass movements of bird, bat, and insect migration, but it is still unknown how many of these systems perform with regard to detection and quantification of migration intensities of the different groups. In this study that was undertaken within five regions across Europe and the Middle East we examined to what extent bird migration intensities derived from different weather radars are comparable between each other and relate to intensities measured by local small‐scaled radars, some of them specifically developed to monitor birds. Good correspondence was found for the relative day‐to‐day pattern in migration intensities among most radar systems that were compared. Absolute intensities varied between different systems and regions. The findings of this study can be used to infer about absolute bird migration intensities measured by different radar systems and consequently help resolving methodological issues regarding the estimation of migrant numbers in the Western‐Palearctic region. It further depicts a scientific basis for the future monitoring of migratory bird populations across a large spatio‐temporal scale, predicting their movements and studying its consequences on ecological systems and human lives.Item Effects of a sea barrier on large-scale migration patterns studied by a network of weather radars(2018-04-03) Weisshaupt, Nadja; Dokter, Adriaan M.; Arizaga, Juan; Maruri, Mercedes; WEATHER AND CLIMATE INTELLIGENCE FOR BUSINESSCapsule: Nocturnal passerine migration patterns were studied by a network of weather radars within the East-Atlantic flyway providing large-scale information on the effect of a geographical barrier. Aims: The aim of this study was to obtain a large-scale spatial overview of the effects of a sea barrier on migratory flyways in northern Spain/western France. Methods: Weather radar data were used from five sites at the Bay of Biscay during nights in spring 2015 to calculate flight directions and migration traffic rates (MTRs). Results: The highest MTRs were registered by the radars at the southeastern edge of the bay, with a gradual decrease northwards. Spring migration direction was generally NNE/NE. Continuous nocturnal migration pattern indicated migration over land in the south. The radar half way up the French coast exhibited bimodal migration intensities at night, indicating sea crossing, and the northernmost corner of the bay showed little migration. Conclusions: Radar patterns indicated migration over land and sea during spring migration. Sea crossing occurred with flight distances of up to about 500 km. Most migration activity was observed in the radars along the southeastern section of the bay, indicating that the general migration flyway from Spain funnels through the eastern side of the north Iberian Peninsula.Item Nocturnal bird migration in the Bay of Biscay as observed by a thermal-imaging camera(2016-10-01) Weisshaupt, Nadja; Maruri, Mercedes; Arizaga, Juan; WEATHER AND CLIMATE INTELLIGENCE FOR BUSINESSCapsule: Bird migration was recorded by an infrared device at three sites in the southeastern Bay of Biscay, indicating seasonal east–west differences in migration flow. Aims: The main aims of this study were to quantify and describe nocturnal migration dynamics in proximity of a sea barrier, and to assess seasonal and geographical drivers of migration patterns. Methods: A thermal-imaging camera was used at two coastal study sites (Punta Galea, Cape Higuer) in spring and three study sites (coast: Punta Galea, Cape Higuer; inland: Iregua Valley) in autumn for four hours from sunset over 90 nights in 2014 and 2015. Results: Migration was strong at both coastal sites in early spring. Autumn migration was weak at the western coast, but strong at the eastern coast and inland. Tailwind had no significant effect on migration intensity, but migration ceased during strong cross- or headwinds despite clear skies. The majority of the targets were passerines. Conclusions: The patterns observed suggest spring migration occurs on a broader front, potentially involving sea crossing further to the west, while autumn migration concentrates more eastwards over land. In both seasons, there was no significant response to wind conditions.Item Radar wind profilers and avian migration: a qualitative and quantitative assessment verified by thermal imaging and moon watching(2017-09) Weisshaupt, Nadja; Lehmann, Volker; Arizaga, Juan; Maruri, Mercedes; WEATHER AND CLIMATE INTELLIGENCE FOR BUSINESSRadars of various types have been used in ornithological research for about 70 years. However, the potential of radar wind profiler (RWP) as a tool for biological purposes remains poorly understood. The aim of this study is to assess the suitability of RWP for ornithological research questions. A 1290 MHz RWP at the south-eastern coast of the Bay of Biscay has been known to exhibit seasonally occurring nocturnal signals attributed to migrating birds. As a first step to verify the origin of these seasonal patterns, historical radar data from 2010 to 2012 were analysed, and both bird patterns and temporal occurrence were identified in RWP data at different levels of the signal processing. A thermal-imaging (TI) camera in conjunction with moon watching was used as verification systems at the radar site to confirm the ornithological origin of the radar echoes. The simultaneous data on spring migration served as a basis for the identification of biological signatures (qualitative parameters) on time-series level (raw data) and to derive quantitative migration parameters (flight altitude, migration traffic rates) thereof. Finally, the quantitative measurements of the TI camera and the radar were compared considering meteorological conditions. The approach allowed identifying reproducible criteria based on time series to calculate migration traffic rates and altitudinal flight distribution. General flight directions were only available in the final wind data. In clear weather conditions, the calibration methods coincided well with the wind profiler data. Findings show that wind profiler raw data offer reliable information on migration intensity, flight altitudes and flight directions in a variety of meteorological conditions. The method presented can be applied as a complement to present efforts to use weather radars for large-scale bird monitoring. Furthermore, it is also interesting for the meteorological community to refine signal-processing methods.Item The role of radar wind profilers in ornithology(2018-07) Weisshaupt, Nadja; Arizaga, Juan; Maruri, Mercedes; WEATHER AND CLIMATE INTELLIGENCE FOR BUSINESSIn the past 70 years radar technology has been increasingly applied in ornithological research in various geographical areas worldwide and has contributed greatly to a better understanding of bird migration. Many different radar types have been used, such as tracking, ship or weather radars. However, radar wind profilers (RWPs) have been largely neglected in avian research. RWPs continuously measure three-dimensional winds and, despite the low frequency range at which these systems operate, available literature provides evidence that birds are recorded at many sites. So far the potential of RWPs in ornithological research has not been fully explored and studies deal predominantly with birds in the context of clutter removal. However, based on their broad implementation in networks (e.g. E-PROFILE in Europe) situated in areas that are strategically important for bird migration, they could offer a valuable complement to already established or planned large-scale bird monitoring schemes by radar. The objective of this paper is to serve as a reference for those who wish to consider RWP data in a biological context. To that end, we provide an overview of the evolution and establishment of operational RWPs as well as of their mode of operation, in order to depict their role in meteorology and to evaluate their potential in ornithology. The assessment is based on available literature on RWPs and radar ornithology outlining the past, present and potential future role of wind profilers. In the past, birds were discarded as contamination and eliminated as far as possible from the meteorological data. Only recently have the echo signatures of biological targets been scrutinized thoroughly in raw data and used successfully for ornithological investigation. On this basis it is possible to consider the potential future utility of this promising data source as a complement to other remote-sensing instruments and other sampling techniques used in avian research. Weather independence of ornithological information was found to be a particular benefit. However, as the development of the bird-specific method is only in an early stage, more detailed studies are necessary in the future to fully assess the potential of this type of radar.