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Data Assimilation for Chaotic Dynamics
Get PDFChaos is ubiquitous in physical systems. The associated sensitivity to initial conditions is a significant obstacle in forecasting the weather and other geophysical fluid flows. Data assimilation is the process whereby the uncertainty in initial conditions is reduced by the astute combination of model predictions and real-time data. This chapter reviews recent findings from investigations on the impact of chaos on data assimilation methods: for the Kalman filter and smoother in linear systems, analytic results are derived; for their ensemble-based versions and nonlinear dynamics, numerical results provide insights. The focus is on characterizing the asymptotic statistics of the Bayesian posterior in terms of the dynamical instabilities, differentiating between deterministic and stochastic dynamics. We also present two novel results. Firstly, we study the functioning of the ensemble Kalman filter in the context of a chaotic, coupled, atmosphere-ocean model with a quasi-degenerate spectrum of Lyapunov exponents, showing the importance of having sufficient ensemble members to track all of the near-null modes. Secondly, for the fully non-Gaussian method of the particle filter, numerical experiments are conducted to test whether the curse of dimensionality can be mitigated by discarding observations in the directions of little dynamical growth of uncertainty. The results refute this option, most likely because the particles already embody this information on the chaotic system. The results also suggest that it is the rank of the unstable-neutral subspace of the dynamics, and not that of the observation operator, that determines the required number of particles. We finally discuss how knowledge of the random attractor can play a role in the development of future data assimilation schemes for chaotic multiscale systems with large scale separation
Going Beyond Counting First Authors in Author Co-citation Analysis
Get PDFThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Get PDF“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Appropriate Similarity Measures for Author Cocitation Analysis
Get PDFWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
Dispelling the Myths Behind First-author Citation Counts
Get PDFWe conducted a full-scale evaluative citation analysis study of scholars in the XML research field to explore just how different from each other author rankings resulting from different citation counting methods actually are, and to demonstrate the capability of emerging data and tools on the Web in supporting more realistic citation counting methods. Our results contest some common arguments for the continued
use of first-author citation counts in the evaluation of scholars, such as high correlations between author rankings by first-author citation counts and other citation
counting methods, and high costs of using more realistic citation counting methods that are not well-supported by the ISI databases. It is argued that increasingly available digital full text research papers make it possible for citation analysis studies to go beyond what the ISI databases have directly supported and to employ more
sophisticated methods
EUPPBench postprocessing benchmark dataset - gridded data - Part I
No full textThe EUMETNET EUPPBench postprocessing benchmark gridded data is an analysis-ready dataset to perform benchmarks of different postprocessing methods on a common dataset.
This dataset is using the Zarr format. Please look at the Zarr documentation to see how to load and access the data.
The documentation of the dataset is available on https://eupp-benchmark.github.io/EUPPBench-doc/ .
The official way to download the dataset is through the climetlab EUMETNET postprocessing benchmark plugin.
This Zenodo repository aims to preserve the dataset by providing long-term storage.
Please read the LICENSE file for more information on the data licenses.
Installation procedure
Download the 3 parts of the dataset
EUPPBench-gridded.part.z01
EUPPBench-gridded.part.z02
EUPPBench-gridded.part.zip
in a given folder, and on a Linux (or mac OS) terminal, and still in this folder, enter the following commands
zip -FF EUPPBench-gridded.part.zip --out EUPPBench-gridded.zip
rm EUPPBench-gridded.part.*
unzip EUPPBench-gridded.zip
This will unpack the dataset. You need at least 250Gb of free space on your disk to perform this operation.
Citation
If you use this dataset for a publication, please cite the dataset article:
Demaeyer, J., Bhend, J., Lerch, S., Primo, C., Van Schaeybroeck, B., Atencia, A., Ben Bouallègue, Z., Chen, J., Dabernig, M., Evans, G., Faganeli Pucer, J., Hooper, B., Horat, N., Jobst, D., Merše, J., Mlakar, P., Möller, A., Mestre, O., Taillardat, M., and Vannitsem, S.: The EUPPBench postprocessing benchmark dataset v1.0, Earth Syst. Sci. Data Discuss. [preprint], https://doi.org/10.5194/essd-2022-465, in review, 2023.
Remark
You might also be interested by the station data part of this dataset also available on Zenodo here: https://doi.org/10.5281/zenodo.7708362
Postprocessing example datasets for the Pythie software
No full textThis dataset is used to showcase in Jupyter notebooks the usage of the Pythie postprocessing software available on GitHub.
We use the ERA5 reanalysis over a large area in Europe from 1997 to 2016 as gridded observations. These reanalysis have been downloaded from the Copernicus Data Store in GRIB format and converted to the NetCDF file format.
The reforecasts files have been download from ECMWF and converted to NetCDF files.
The observation data of the WMO-compliant DWD meteorological station of Soltau from 1997 to 2016.
The station is located at the point 52°57'37.5"N, 9°47'35.0"E. The data have been downloaded from the DWD Climate Data Center.
Gridded reforecast data source
Source www.ecmwf.int
Creative Commons Attribution 4.0 International (CC BY 4.0)
Copyright © 2021 European Centre for Medium-Range Weather Forecasts (ECMWF).
Copernicus ERA5 gridded reanalysis data source
Source https://cds.climate.copernicus.eu/
Copyright © 2021 European Union.
Generated using Copernicus Climate Change Service information 2021.
Hersbach et al. (2018): ERA5 hourly data on single levels from 1979 to present. Copernicus Climate Change Service (C3S) Climate Data Store (CDS). (Accessed on ), doi:10.24381/cds.adbb2d47.
Observation data source
Source: Deutscher Wetterdienst, DWD CDC porta
koamabayili/VECTRON-author-checklist: VECTRON author checklist
No full textWe have done our best to complete the author checklist relating to the use of animals in the hut study. Note that the objective for the hut study was to evaluate the IRS treatment applications for residual efficacy against Anopheles mosquitoes, including the local An. coluzzii mosquito population. Cows were only used to attract mosquitoes into the huts and no tests were carried out directly on the cows. The author checklist is intended for use with studies where experiments are carried out on animals, which is why we have had such difficulty in completing this for the hut study, as many of the questions do not relate to how the cows were used
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