On the Use of Running Trends as Summary Statistics for Univariate Time Series and Time Series Association

Given a time series, running trends analysis (RTA) involves evaluating least squares trends over overlapping time windows of L consecutive time points, with overlap by all but one observation. This produces a new series called the “running trends series,” which is used as summary statistics of the original series for further analysis. In recent years, RTA has been widely used in climate applied research as summary statistics for time series and time series association. There is no doubt that RTA might be a useful descriptive tool, but, despite its general use in applied research, precisely what it reveals about the underlying time series is unclear and, as a result, its interpretation is unclear too. This paper contributes to such interpretation in two ways: 1) an explicit formula is obtained for the set of time series with a given series of running trends, making it possible to show that running trends, alone, perform very poorly as summary statistics for univariate time series and time series association; and 2) an equivalence is established between RTA and the estimation of a (possibly nonlinear) trend component of the underlying time series using a weighted moving average filter. Such equivalence provides a solid ground for RTA implementation and interpretation/validation. In this respect, the authors propose as diagnostic tools for RTA 1) the plot of the original series, with RTA trend estimation superposed, 2) the average R2 value and the percentage of statistically significant running trends across windows, and 3) the plot of the running trends series with the corresponding confidence intervals.This work has been supported by Projects CGL2010-12153-E and AYA2010-22039-C02-01 from the Spanish Department of Science and Innovation (MICINN)

Detection of a New Large Free Core Nutation Phase Jump

We announce the detection of a new large jump in the phase of the free core nutation (FCN). This is only the second such large FCN phase jump in more than thirty years of FCN monitoring by means of a very long baseline interferometry (VLBI) technique. The new event was revealed and confirmed by analyzing two FCN models derived from a long-time series of VLBI observations. The jump started in 2021 and is expected to last until the late fall of 2022. The amplitude of the phase jump is expected to be approximately 3 rad, which is as much as 1.5 times larger than the first phase jump in 1999–2000. A connection of the new FCN phase jump with the recent geomagnetic jerk started in 2020 is suggested.Santiago Belda was partially supported by Generalitat Valenciana (SEJIGENT/2021/001), the European Union–Next Generation EU (ZAMBRANO 21-04) and Ministerio de Ciencia e Innovación (Spanish Project PID2020-119383GB-I00)

On the decorrelation filtering of RL05 GRACE data for global applications

In autumn 2012, the new release 05 (RL05) of monthly geopotencial spherical harmonics Stokes coefficients (SC) from GRACE (Gravity Recovery and Climate Experiment) mission was published. This release reduces the noise in high degree and order SC, but they still need to be filtered. One of the most common filtering processing is the combination of decorrelation and Gaussian filters. Both of them are parameters dependent and must be tuned by the users. Previous studies have analyzed the parameters choice for the RL05 GRACE data for oceanic applications, and for RL04 data for global application. This study updates the latter for RL05 data extending the statistics analysis. The choice of the parameters of the decorrelation filter has been optimized to: (1) balance the noise reduction and the geophysical signal attenuation produced by the filtering process; (2) minimize the differences between GRACE and model-based data; (3) maximize the ratio of variability between continents and oceans. The Gaussian filter has been optimized following the latter criteria. Besides, an anisotropic filter, the fan filter, has been analyzed as an alternative to the Gauss filter, producing better statistics.This work has been partly supported by two Spanish Projects from CGL2010-12153-E and AYA2010-22039-C02-01; and two from Generalitat Valenciana, GV/2013/144 and ACOMP-2013-068

Differential annotation of tRNA genes with anticodon CAT in bacterial genomes

We have developed three strategies to discriminate among the three types of tRNA genes with anticodon CAT (tRNA(Ile), elongator tRNA(Met) and initiator tRNA(fMet)) in bacterial genomes. With these strategies, we have classified the tRNA genes from 234 bacterial and several organellar genomes. These sequences, in an aligned or unaligned format, may be used for the identification and annotation of tRNA (CAT) genes in other genomes. The first strategy is based on the position of the problem sequences in a phenogram (a tree-like network), the second on the minimum average number of differences against the tRNA sequences of the three types and the third on the search for the highest score value against the profiles of the three types of tRNA genes. The species with the maximum number of tRNA(fMet) and tRNA(Met) was Photobacterium profundum, whereas the genome of one Escherichia coli strain presented the maximum number of tRNA(Ile) (CAT) genes. This last tRNA gene and tilS, encoding an RNA-modifying enzyme, are not essential in bacteria. The acquisition of a tRNA(Ile) (TAT) gene by Mycoplasma mobile has led to the loss of both the tRNA(Ile) (CAT) and the tilS genes. The new tRNA has appropriated the function of decoding AUA codons

Implementación de metodologías de evaluación continua: aplicación en la asignatura de Cálculo Numérico

La creación del nuevo Espacio Europeo de Educación Superior, con los consiguientes cambios en la estructura y contenidos de las titulaciones universitarias, ofrece una gran oportunidad para revisar las metodologías de aprendizaje, estando las metodologías de evaluación continua en una creciente expansión. El objetivo de este trabajo es investigar el efecto que tiene en el aprendizaje de los estudiantes diferentes metodologías de evaluación continua. Para ello, varios tipos de evaluación periódica (entrega de trabajos grupales y/o individuales, exámenes parciales, etc.) han sido puestos en práctica en la asignatura de Cálculo Numérico del último curso de la Licenciatura de Matemáticas y actual Grado de Matemáticas, a lo largo de un total de 14 años académicos en la Universidad de Alicante. En esta comunicación presentaremos las diferentes estrategias de desarrollo de los contenidos de la asignatura así como la forma de evaluación de los mismos. Además, se hará un análisis descriptivo de los resultados obtenidos con las distintas metodologías empleadas y se recogerán propuestas de mejora de cara al próximo curso

Changes in Onset of Vegetation Growth on Svalbard, 2000–2020

The global temperature is increasing, and this is affecting the vegetation phenology in many parts of the world. The most prominent changes occur at northern latitudes such as our study area, which is Svalbard, located between 76°30′N and 80°50′N. A cloud-free time series of MODIS-NDVI data was processed. The dataset was interpolated to daily data during the 2000–2020 period with a 231.65 m pixel resolution. The onset of vegetation growth was mapped with a NDVI threshold method which corresponds well with a recent Sentinel-2 NDVI-based mapping of the onset of vegetation growth, which was in turn validated by a network of in-situ phenological data from time lapse cameras. The results show that the years 2000 and 2008 were extreme in terms of the late onset of vegetation growth. The year 2020 had the earliest onset of vegetation growth on Svalbard during the 21-year study. Each year since 2013 had an earlier or equally early timing in terms of the onset of the growth season compared with the 2000–2020 average. A linear trend of 0.57 days per year resulted in an earlier onset of growth of 12 days on average for the entire archipelago of Svalbard in 2020 compared to 2000.This work (S.R.K.) was supported by the Research Council of Norway under the project Svalbard Integrated Arctic Earth Observing System—Infrastructure Development of the Norwegian Node (SIOS-InfraNor Project No. 269927). This SIOS project (InfraNord instrument #51) is funded by the Norwegian Space Agency (NoSA). The research was also partially funded (S.R.K., H.T.) by the Horizon 2020 project ArcticHubs, grant agreement no 869580. This work (S.B.) was also partially supported by Generalitat Valenciana (SEJIGENT/2021/001), the European Union–Next Generation EU (ZAMBRANO 21-04), and European Research Council (ERC) under the ERC-2017-STG SENTIFLEX project (grant agreement 755617)

Deep ensemble geophysics-informed neural networks for the prediction of celestial pole offsets

Celestial Pole Offsets (CPO), denoted by dX and dY, describe the differences in the observed position of the pole in the celestial frame with respect to a certain precession-nutation model. Precession and nutation components are part of the transformation matrix between terrestrial and celestial systems. Therefore, various applications in geodetic science such as high-precision spacecraft navigation require information regrading precession and nutation. For this purpose, CPO can be added to the precession-nutation model to precisely describe the motion of the celestial pole. However, as Very Long Baseline Interferometry (VLBI) – currently the only technique providing CPO – requires long data processing times resulting in several weeks of latency, predictions of CPO become necessary. Here we present a new methodology named Deep Ensemble Geophysics-Informed Neural Networks (DEGINNs) to provide accurate CPO predictions. The methodology has three main elements: (1) deep ensemble learning to provide the prediction uncertainty; (2) broad-band Liouville equation as a geophysical constraint connecting the rotational dynamics of CPO to the atmospheric and oceanic Effective Angular Momentum functions (EAM); and (3) coupled oscillatory recurrent neural networks to model the sequential characteristics of CPO time series, also capable of handling irregularly-sampled time series. To test the methodology, we use the newest version of the final CPO time series of International Earth Rotation and Reference Systems Service (IERS), namely IERS 20 C04. We focus on a forecasting horizon of 90 days, the practical forecasting horizon needed in space-geodetic applications. Furthermore, for validation purposes we generate an independent global VLBI solution for CPO since 1984 up to the end of 2022 and analyze the series. We draw the following conclusions. First, the prediction performance of DEGINNs demonstrates up to 25% and 33% improvement respectively for dX and dY, with respect to the rapid data provided by IERS. Second, predictions made with the help of EAM are more accurate compared to those without EAM, thus providing a clue to the role of atmosphere and ocean on the excitation of CPO. Finally, free core nutation period shows temporal variations with a dominant periodicity of around one year, partially excited by EAM.Santiago Belda was partially supported by Generalitat Valenciana (SEJIGENT/2021/001), the European Union—NextGenerationEU (ZAMBRANO 21-04) and Ministerio de Ciencia e Innovación (MCIN/AEI/10.13039/501100011033/). Maria Karbon was supported by PROMETEO/2021/030 funded by Generalitat Valenciana

Compact Integration of a GSM-19 Magnetic Sensor with High-Precision Positioning using VRS GNSS Technology

Magnetic data consists of a sequence of collected points with spatial coordinates and magnetic information. The spatial location of these points needs to be as exact as possible in order to develop a precise interpretation of magnetic anomalies. GPS is a valuable tool for accomplishing this objective, especially if the RTK approach is used. In this paper the VRS (Virtual Reference Station) technique is introduced as a new approach for real-time positioning of magnetic sensors. The main advantages of the VRS approach are, firstly, that only a single GPS receiver is needed (no base station is necessary), reducing field work and equipment costs. Secondly, VRS can operate at distances separated 50–70 km from the reference stations without degrading accuracy. A compact integration of a GSM-19 magnetometer sensor with a geodetic GPS antenna is presented; this integration does not diminish the operational flexibility of the original magnetometer and can work with the VRS approach. The coupled devices were tested in marshlands around Gandia, a city located approximately 100 km South of Valencia (Spain), thought to be the site of a Roman cemetery. The results obtained show adequate geometry and high-precision positioning for the structures to be studied (a comparison with the original low precision GPS of the magnetometer is presented). Finally, the results of the magnetic survey are of great interest for archaeological purposes

Evaluación continua a través del trabajo autónomo del estudiante

Durante el curso académico 2014-2015 se han introducido distintas mejoras en la metodología docente y en el sistema de evaluación de la asignatura Fundamentos Matemáticos de la Ingeniería II del primer curso del Grado en Ingeniería Civil de la Universidad de Alicante. Su objetivo es reducir el tiempo dedicado a la clase magistral en el desarrollo de la asignatura, en aras de fomentar la participación del alumnado. También se pretende conseguir un mayor aprovechamiento de las clases prácticas mediante la resolución autónoma de diversos ejercicios y problemas por parte de los alumnos, contando con la supervisión del profesorado. Este último aspecto es fundamental en las materias propias de las Matemáticas. En esta comunicación detallaremos las acciones específicas adoptadas con estos fines, tanto en la dinámica de las clases como en la forma de evaluación. Así mismo, se realizará un análisis cuantitativo y cualitativo de los resultados alcanzados y de las percepciones que profesores y alumnos tienen sobre los cambios introducidos

Inter-Comparison of UT1-UTC from 24-Hour, Intensives, and VGOS Sessions during CONT17

This work focuses on the assessment of UT1-UTC estimates from various types of sessions during the CONT17 campaign. We chose the CONT17 campaign as it provides 15 days of continuous, high-quality VLBI data from two legacy networks (S/X band), i.e., Legacy-1 (IVS) and Legacy-2 (VLBA) (having different network geometry and are non-overlapping), two types of Intensive sessions, i.e., IVS and Russian Intensives, and five days of new-generation, broadband VGOS sessions. This work also investigates different approaches to optimally compare dUT1 from Intensives with respect to the 24 h sessions given the different parameterization adopted for analyzing Intensives and different session lengths. One approach includes the estimation of dUT1 from pseudo Intensives, which are created from the 24 h sessions having their epochs synchronized with respect to the Intensive sessions. Besides, we assessed the quality of the dUT1 estimated from VGOS sessions at daily and sub-daily resolution. The study suggests that a different approach should be adopted when comparing the dUT1 from the Intensives, i.e., comparison of dUT1 value at the mean epoch of an Intensive session. The initial results regarding the VGOS sessions show that the dUT1 estimated from VGOS shows good agreement with the legacy network despite featuring fewer observations and stations. In the case of sub-daily dUT1 from VGOS sessions, we found that estimating dUT1 with 6 h resolution is superior to other sub-daily resolutions. Moreover, we introduced a new concept of sub-daily dUT1-tie to improve the estimation of dUT1 from the Intensive sessions. We observed an improvement of up to 20% with respect to the dUT1 from the 24 h sessions.The publication costs are supported within the funding programme “Open Access Publikationskosten” Deutsche Forschungsgemeinschaft (DFG, German Research Foundation)—Project Number 491075472. K.B. is funded by the Deutsche Forschungsgemeinschaft (DFG, German Research Foundation)– Project-ID 434617780—SFB 1464 (TerraQ). S.B. was partially supported by Generalitat Valenciana (SEJIGENT/2021/001), the European Union—NextGenerationEU (ZAMBRANO 21-04) and Ministerio de Ciencia e Innovación (Spanish Project PID2020-119383GB-I00)