A composite approach to produce reference datasets for extratropical cyclone tracks: application to Mediterranean cyclones

Many cyclone detection and tracking methods (CDTMs) have been developed in the past to study the climatology of extratropical cyclones. However, all CDTMs have different approaches in defining and tracking cyclone centers. This naturally leads to cyclone track climatologies with inconsistent physical characteristics. More than that, it is typical for CDTMs to produce a non-negligible number of tracks of weak atmospheric features, which do not correspond to large-scale or mesoscale vortices and can differ significantly between CDTMs. Lack of consensus in CDTM outputs and the inclusion of significant numbers of uncertain tracks therein have long prohibited the production of a commonly accepted reference dataset of extratropical cyclone tracks. Such a dataset could allow comparable results on the analysis of storm track climatologies and could also contribute to the evaluation and improvement of CDTMs. To cover this gap, we present a new methodological approach that combines overlapping tracks from different CDTMs and produces composite tracks that concentrate the agreement of more than one CDTM. In this study we apply this methodology to the outputs of 10 well-established CDTMs which were originally applied to ERA5 reanalysis in the 42-year period of 1979-2020. We tested the sensitivity of our results to the spatiotemporal criteria that identify overlapping cyclone tracks, and for benchmarking reasons, we produced five reference datasets of subjectively tracked cyclones. Results show that climatological numbers of composite tracks are substantially lower than the ones of individual CDTMs, while benchmarking scores remain high (i.e., counting the number of subjectively tracked cyclones captured by the composite tracks). Our results show that composite tracks tend to describe more intense and longer-lasting cyclones with more distinguished early, mature and decay stages than the cyclone tracks produced by individual CDTMs. Ranking the composite tracks according to their confidence level (defined by the number of contributing CDTMs), it is shown that the higher the confidence level, the more intense and long-lasting cyclones are produced. Given the advantage of our methodology in producing cyclone tracks with physically meaningful and distinctive life stages, we propose composite tracks as reference datasets for climatological research in the Mediterranean. The Supplement provides the composite Mediterranean tracks for all confidence levels, and in the conclusion we discuss their adequate use for scientific research and applications

A composite approach to produce reference datasets for extratropical cyclone tracks: application to Mediterranean cyclones

Many cyclone detection and tracking methods (CDTMs) have been developed in the past to study the climatology of extratropical cyclones. However, all CDTMs have different approaches in defining and tracking cyclone centers. This naturally leads to cyclone track climatologies with inconsistent physical characteristics. More than that, it is typical for CDTMs to produce a non-negligible number of tracks of weak atmospheric features, which do not correspond to large-scale or mesoscale vortices and can differ significantly between CDTMs. Lack of consensus in CDTM outputs and the inclusion of significant numbers of uncertain tracks therein have long prohibited the production of a commonly accepted reference dataset of extratropical cyclone tracks. Such a dataset could allow comparable results on the analysis of storm track climatologies and could also contribute to the evaluation and improvement of CDTMs. To cover this gap, we present a new methodological approach that combines overlapping tracks from different CDTMs and produces composite tracks that concentrate the agreement of more than one CDTM. In this study we apply this methodology to the outputs of 10 well-established CDTMs which were originally applied to ERA5 reanalysis in the 42-year period of 1979–2020. We tested the sensitivity of our results to the spatiotemporal criteria that identify overlapping cyclone tracks, and for benchmarking reasons, we produced five reference datasets of subjectively tracked cyclones. Results show that climatological numbers of composite tracks are substantially lower than the ones of individual CDTMs, while benchmarking scores remain high (i.e., counting the number of subjectively tracked cyclones captured by the composite tracks). Our results show that composite tracks tend to describe more intense and longer-lasting cyclones with more distinguished early, mature and decay stages than the cyclone tracks produced by individual CDTMs. Ranking the composite tracks according to their confidence level (defined by the number of contributing CDTMs), it is shown that the higher the confidence level, the more intense and long-lasting cyclones are produced. Given the advantage of our methodology in producing cyclone tracks with physically meaningful and distinctive life stages, we propose composite tracks as reference datasets for climatological research in the Mediterranean. The Supplement provides the composite Mediterranean tracks for all confidence levels, and in the conclusion we discuss their adequate use for scientific research and applications.</p

Turnover of passerine birds on islands in the Aegean Sea (Greece)

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/73442/1/j.1365-2699.2007.01695.x.pd

Symbolic analysis and simulation for power system dynamic performance assessment

2005 IEEE Power Engineering Society General Meeting -- 12 June 2005 through 16 June 2005 -- San Francisco, CA -- 65870This paper presents a MATLAB-based Voltage Stability Toolbox (VST) designed to analyze bifurcations, voltage stability problems and nonlinear observability in electric power systems. VST combines proven computational and analytical capabilities of stability and observability theory, symbolic implementation and graphical representation capabilities of MATLAB and its Toolboxes. The motivation for developing the package is to provide a flexible simulation environment for ongoing research conducted at Drexel University's Center for Electric Power Engineering (CEPE), and to enhance undergraduate/graduate power engineering courses. VST is a very flexible tool for load flow, small-signal and transient stability, bifurcation and observability analysis. To illustrat 1e the capabilities of VST, simulations using the IEEE 14 bus system are presented. ©2005 IEEE

Interleaving Angle Variation Analysis for Variable Frequency PWM Drives

Generally, drive manufacturers include input filters and/or output filters to meet system requirements. Depending on damping, these filters have the potential to introduce resonant conditions. Often the switching frequency changes with the rotational speed of the drive machine leading to the possibility that switching harmonics align with the resonant peak of the filters. As the frequency of the drive decreases, the number of pulses per half cycle of the output fundamental can increase to maintain a reasonably constant switching frequency. For drives that utilize interleaving, another possibility investigated in this paper is to dynamically alter the phase angle between interleaved converters. This allows selective elimination of harmonics near the filter resonance while reducing losses due to a lower switching frequency. Typically, the phase shift is based on the number of system inverters and is used to increase the effective switching frequency. The phase-shifting strategy in this paper differs from the traditional method by targeting specific harmonics of interest. This paper¹ describes the details of implementing strategies to dynamically alter the phase shift between interleaved converters to eliminate harmonics.Naval Surface Warfare Center Philadelphia Divisio

Simulink model for hybrid power system test-bed

Paper presented at the Institute of Electrical and Electronics Engineers Electric Ship Technologies Symposium, ESTS 2007, Arlington, VA.The Hybrid Power System Test-bed currently being constructed at NAVSEA Philadelphia is designed to serve as a developmental platform for the evaluation of hybrid power and propulsion options related to unmanned surface vehicles (USVs). Prior to component integration, a Matlab/Simulink model of the test-bed was created to simulate the system interactions and assist in the detailed electrical design. A reduced order system model was required before a detailed analysis of the individual components was performed. This paper describes the evolution of the test-bed model and the work to date in developing detailed component models for the system