dataesr/scientific-paragraphs-categorization huggingface dataset:
CONCLUSION In this article, we present the system architecture and estimation methods of CoronaSurveys, which uses open surveys to monitor the progress of the COVID-19 pandemic. Our graphical  estimations require large amounts of data from active participants, but provide insightful depictions of the progress of the pandemic in different regions, offering an estimation of the cumulative and active number of cases in different geographical areas. The most important challenge and limitation of CoronaSurveys is the number of survey responses. In this sense, the dissemination of our graphical estimations is important to maximize user engagement and retention. For this reason, in the future we aim to include a forecast of the number of cases and fatalities based on recent data for different geographical areas, in order to empower the dissemination of our graphical visualizations and with it increase user recruitment.
The geochemical modeling approach using PHREEQC software was used to model pH evolution and main element release as a function of the added amount of acid or base over the entire pH range: 1 < pH < 13. For calcareous matrices (sand with calcite), the results are typical of a carbonated environment, the geochemistry of which is well known. For matrices containing pyrite, the results identify different pH values favoring the dissolution of pyrite: pH = 2 in a pyrite-only environment and pH = 6 where pyrite coexists with calcite. The neutral conditions can be explained by the buffering capacity of calcite, which allows iron oxyhydroxide precipitation. Major element release is then related to the dissolution and precipitation of the mineral assemblages. The geochemical modeling allows the prediction of element speciation in the solid and liquid phases.
Geochemical Modeling The geochemical modeling was implemented using PHREEQC software (interactive version alpha 3. 1. 2. 8538, United States Geological Survey). This makes it possible to conceptually represent the experiments. PHREEQC, on the basis of a deterministic approach, proposes a thermodynamic model. All chemical reactions and related equations are resolved by the software's numerical tools  [34]. The llnl reference database (Lawrence Livermore National Laboratory) was used, as it enrolls many mineral phases. The geochemical modeling was used to fit the ANC-BNC titrations and, thus, test several hypotheses on the geochemical processes and element release and speciation  [35]. Several scenarios were tested regarding the amounts of mineral phases submitted to ANC-BNC titrations and the phases expected to form following the dissolution of the original mineral assemblages.
In this study, only the final optimal model is presented, although it resulted from a large number of runs (~100 models for calcite/SiO 2 and pyrite/SiO 2 alone and 200 models for calcite/pyrite/SiO 2 ). The thermodynamic constants implemented in the llnl database were never changed; only the initial mineral assemblage and the list of phases allowed to form or dissolve were optimized. The final model was defined by the solid and gaseous phase and their initial contents (mineral assemblage for the solid phase), the amount of base or acid added to the system, and the list of phases that were not initially in the mixture but were expected to form and potentially dissolve, defining transitional states (from a thermodynamic point of view). For the gaseous phase, as the batches were opened during the experiment to avoid overpressurization and the risk of explosion, the batch reactors were considered as partially opened.
Acknowledgments: The authors would like to thank Nathalie Dumont and David Lebouil (Laboratoire Déchets Eau Environnement Pollutions, DEEP) and Myriam Hammada (Laboratories d'Ecologie des Hydrosystèmes Naturels et Anthropisés, LEHNA) for technical assistance and analytical analyses. The authors are grateful to the field observatory for urban water management (OTHU) and CNRS EC2CO for their logistical and financial support.
In this context, several scientific teams are working on the development of new internal-tide models, taking advantage of the very long altimeter time series now available, which represent an unprecedented and valuable global ocean database. The internal-tide models presented here focus on the coherent internal-tide signal and they are of three types: empirical models based upon analysis of existing altimeter missions, an assimilative model and a three-dimensional hydrodynamic model. A detailed comparison and validation of these internaltide models is proposed using existing satellite altimeter databases. The analysis focuses on the four main tidal constituents: M 2 , K 1 , O 1 and S 2. The validation process is based on a statistical analysis of multi-mission altimetry including Jason-2 and Cryosphere Satellite-2 data.
Introduction Since the early 1990s, several altimeter missions have been monitoring sea level at a global scale, nowadays offering a long and very accurate time series of measurements. This altimetry database is nearly homogeneous over the entire ocean, allowing the sampling of many regions that were poorly sampled or not sampled at all before the satellite era. Thanks to its current accuracy and maturity, altimetry is now regarded as a fully operational observing system dedicated to ocean and climate applications  (Escudier et al. , 2017). The main difficulty encountered when using altimeter datasets for ocean studies is related to the long revisit time of the satellites, which results in the aliasing of high-frequency ocean signals into a much lower-frequency band. Concerning tidal frequencies, the 9.
9156 d cycle of TOPEX/Poseidon and Jason altimeter series induces the aliasing of the semidiurnal M 2 lunar tide into a 62 d period, and the diurnal K 1 tide is aliased into a 173 d period, the latter of which is very close to the semiannual frequency and raises complex separation problems. The long duration of the global ocean altimeter database available has allowed the community to overcome this separation problem, and new global ocean barotropic tidal solutions  (Stammer et al. , 2014)  have been produced taking advantage of altimeter data: among them the last Goddard/Grenoble Ocean Tide model (denoted GOT:  Ray, 2013)  and the last finite-element solution for ocean tide (denoted FES2014:  Carrere et al. , 2016a; Lyard et al. , 2020) , which are commonly used as reference for the barotropic tide correction in actual altimeter geophysical data records (denoted GDRs).
Moreover this altimeter database has been used in numerous studies to validate new instrumental and geophysical corrections used in altimetry, thanks to the analysis of their impact on the sea level estimation at climate scales, as well as at lower temporal scales like mesoscale signals; in particular, it has proven its efficiency for validating global ocean models  (Shum 1997; Stammer et al. , 2014; Carrere et al. , 2016b; Quartly et al. , 2017). The upcoming Surface Water Ocean Topography (SWOT) mission, led by NASA, CNES, and the UK and Canadian space agencies, is planned for 2021 and will measure sea surface height with a spatial resolution never proposed before, thus raising the importance of the correction of the internaltide surface signature. Internal tides (denoted ITs) are generated by an incoming barotropic tidal flow on a bathymetric pattern within a stratified ocean and can have amplitudes of several tens of meters at the thermocline level and a signature of several centimeters at the surface, with wavelengths ranging approximately between 30 and 250 km for the lowest three modes of variability  (Chelton et al.
, 2014). In this context, and since conventional satellite altimetry has already shown its ability to detect small-scale internaltide surface signatures  (Ray and Mitchum, 1997; Dushaw 2002; Carrere et al. , 2004) , several scientific teams have developed new internal-tide models, taking advantage of the very long altimeter time series now available. These internal-tide models are of three types: empirical models based upon analysis of existing altimeter missions, usually more than one; assimilative models based upon assimilating altimeter data into a reduced-gravity model; and three-dimensional hydrodynamic models, which embed internal tides into an eddying general circulation model. In the present paper, the analysis is focused on seven models that yield a coherent internal-tide solution:  Dushaw (2015) ,  Egbert and Erofeeva (2014) ,  Ray and Zaron (2016) ,  Shriver et al.
(2014) , Clément Ubelmann  (personal communication, 2017) ,  Zaron (2019) , and  Zhao et al. (2016 Zhao et al. ( , 2019a)). The objective of this paper is to present a detailed comparison and a validation assessment of these internal-tide models using satellite altimetry. The present analysis focuses on the coherent internal-tide signal for the main tidal constituents: M 2 , S 2 , K 1 and O 1. The validation process is based on a statistical analysis and on a comparison to multi-mission altimetry including Jason-2 (denoted J2 hereafter) and Cryosphere Satellite-2 (also named CryoSat-2 or C2 hereafter) LRM data (low-resolution mode). For the sake of clarity, only results for the main tidal components M 2 and K 1 are presented in the core of this paper, and O 1 and S 2 validation results are gathered in the Appendix.
After a brief description of the participating models (Sect. 2), an analysis of the differences between internal-tide models is presented in Sect. 3. Section 4 describes the altimeter dataset used, the method of comparison and the validation strategy. The validation results of the different internaltide corrections versus altimetry databases are described in Sects. 5 and 6. Finally, a discussion and concluding remarks are gathered in Sect. 7. Ocean  Sci. , 17, 147-180, 2021  https://doi. org/10. 5194/os-17-147-2021 2 Presentation of participating internal-tide models This section gives a brief overview of the internal-tide models evaluated in this study. We considered five purely empirical models involving data merging, one data assimilative model and also one pure hydrodynamic model simulating tides and internal tides using the gravitational forcing and a high spatial resolution but without any internal-tide data constraint.
DUSHAW This global model was computed using a frequencywavenumber tidal analysis  (Dushaw et al. , 2011; Dushaw, 2015). The internal tides were assumed to be composed of narrow-band spectra of traveling waves, and these waves are fitted to the altimeter data in both time and position. A tidal analysis of a time series allows extracting accurate tidal estimates from noisy or irregular data under the assumptions that the signal is temporally coherent and described by a few known frequencies. The frequency-wavenumber analysis generalizes such an analysis to include the spatial dimension, making the strong assumptions that both time and spatial wave variations are coherent. In addition to the known tidal constituent frequencies, the solution also requires accurate values for the local intrinsic wavelengths of low-mode internal waves.
Internal-tide properties, which depend on inertial frequency, stratification and depth, were derived using the 2009 World Ocean Atlas  (Antonov et al. , 2010; Locarnini et al. , 2010)  and Smith and Sandwell global seafloor topography  (Smith and Sandwell, 1997). The solution is a spectral model with no inherent grid resolution; tidal quantities of interest derived from the solution are both inherently consistent with the data employed and influenced by non-local data. The fit used M 2 , S 2 , N2, K2, O 1 and K 1 constituents, with spectral bands for barotropic, mode-1 and mode-2 wavenumbers. Data from the TOPEX/Poseidon (TP) and Jason-1 altimetry programs were employed. These data had the barotropic tides removed, but the fit allowed for residual barotropic variations. Employing all constituents and wavelengths simultaneously in a single fit minimized the chance that the solution for a particular constituent was influenced by noise from nearby tidal constituents.
RAY The RAY model provides a global chart of surface elevations associated with the stationary M 2 internal-tide signal. This map is empirically constructed from multi-mission satellite altimeter data, including GFO (GEOSAT Follow-On), ERS (European Remote Sensing satellite), Envisat, TOPEX/Poseidon, and the J1 and J2 missions. Although the present-day altimeter coverage is not entirely adequate to support a direct mapping of very short-wavelength features such as surface internal-tide signatures, using an empirical mapping approach produces a model that is independent of any assumption about ocean wave dynamics. The along-track data from each satellite mission were subjected to tidal analysis, and the M 2 fields were high-pass-filtered to remove residual noise from barotropic and other longwavelength modeling errors.
Conventional harmonic analysis is then used to compute harmonic constants at each point along the nominal 1 Hz ground tracks  (Carrere et al. , 2004) , and these data are used as inputs for subsequent steps. HRET was initially developed to evaluate plausible spatial models for the baroclinic tides, seeking ways to improve on some previous models  (Zhao et al. , 2012; Ray and Zaron, 2016). It uses a local representation of the wave field as a sum of waves modulated by an amplitude envelope consisting of a second-order polynomial, thus generalizing the spatial signal model used in previous plane wave fitting  (Ray and Mitchum, 1997; Zhao et al. , 2016). The details of the implementation in HRET differ in additional ways from previous approaches. Specifically, the wavenumber modulus and direction of each wave component are determined by local two-dimensional Fourier analysis of the along-track data, and the coefficients in the spatial model are determined by weighted least-squares fitting to along-track slope data -the latter removes the need for rather arbitrary along-track high-pass filtering used in other estimates.
Assimilative model Gary D. Egbert and Svetlana Y. Erofeeva have developed a reduced-gravity (RG) data assimilation scheme for mapping low-mode coherent internal tides  (Egbert and Erofeeva, 2014)  and applied this to a multi-mission dataset to produce global first mode M 2 and K 1 solutions. This scheme is based on the Boussinesq linear equations for flow over arbitrary topography with a free surface and horizontally uniform stratification. As in  Tailleux and McWilliams (2001)  and  Griffiths and Grimshaw (2007) , vertical dependence of the flow variables are described using flat-bottom modes (which depend on the local depth H (x, y)), yielding a coupled system of (two-dimensional) partial differential equations (PDEs) for the modal coefficients for surface elevation and horizontal velocity.
Equations for each mode are coupled through in-teraction coefficients, which can be given in terms of the vertical-mode eigenvalues following the approach of  Griffiths and Grimshaw (2007). Modes are decoupled wherever bathymetric gradients are zero, and for a flat bottom the system reduces to the usual single-mode RG shallow-water equations. Within the RG scheme used, the vertical-mode coupling terms are dropped to obtain independent equations for the propagation of each mode with spatially variable reduced water depth, which are determined from local bathymetry and stratification. These simplified equations are identical to the linear shallow-water equations used in the OSU Tidal Inversion Software (OTIS, https://www. tpxo. net/otis, last access: 17 December 2020;  Egbert and Erofeeva, 2002) , thus allowing the use of the assimilation system to map internal tides by simply modifying depth and fitting along-track harmonic constants as a sum over a small number of modes.
102 on year 2014) has been run and a harmonic analysis of the steric 1 h SSH allowed the extraction of the M 2 internal-tide signal which remains coherent in this period. The non-assimilative quality of the simulation makes it entirely independent from the altimeter database used for the validation. The spatial resolution of the native grid is 1/24 A first analysis of the model differences consists in visualizing the patterns of IT models' amplitude in the regions of interest defined in Fig. 1. These seven regions are characterized by a well-known and nearly permanent internal-tide signal, already pointed out by previous studies  (Egbert et al. , 2000; Carrere et al. , 2004; Nugroho, 2017). From the seven regions of interest, the North Pacific area (NPAC) and Luzon regions were selected for the comparison hereafter because they are more energetic regions; moreover, all tested models are available in the NPAC region and the Luzon area is characterized by strong semidiurnal and diurnal baroclinic tides.
aviso. altimetry. fr/en/missions. html, last access: 17 December 2020). For the purpose of the present study, we use the databases for two different missions: -Jason-2 (denoted J2 in the text and figures) is a reference mission flying in the reference TP track with a 10 d cycle and sampling latitudes between ± 66   -CryoSat-2 (denoted C2 hereafter) is characterized by a drifting polar orbit sampling all polar seas and it has a nearly repetitive sub-cycle of about 29 d. The mission's time series and the number of cycles used for the present study are listed in Table  3. It is worth pointing out that much of the T/P and Jason data have been used in most of the IT empirical solutions tested (see Table  1 ), but all models are independent of CryoSat-2 mission data. Due to sub-optimal time sampling, altimeters alias the tidal signal to much longer periods than the actual tidal period.
Method of comparison Satellite altimetry databases can be used to evaluate many geophysical corrections and particularly global barotropic tidal models as already examined by other authors  (Stammer et al. , 2014; Carrere et al. , 2016a, b; Lyard et al. , 2006; Carrere, 2003). We propose using a similar approach to validate the concurrent IT models listed in Table  1. First, we generate the corresponding IT correction for each along-track altimeter measurement, computed from the interpolation of each IT atlas onto the satellites' ground tracks and the use of a tidal prediction algorithm. Each tidal component is considered separately for the clarity of the analysis, keeping in mind that the various IT models do not all contain the same waves. Second, the altimeter SSH using IT corrections from each model tested can then be computed, and the differences in the sea level contents are analyzed for different time and spatial scales.
Variance reduction analysis using satellite altimeter data This section gathers the validation results of each IT model using the satellite altimetry databases described previously. For the clarity of the analysis, each IT correction is compared to a reference correction using a ZERO correction. For the ZERO correction, no IT correction is applied, as in the actual altimeter geophysical data records version-D and version-E (GDR-D and GDR-E) processing  (Pujol et al. , 2016; Taburet et al. , 2019). The complete diagnostics and analysis are presented hereafter for the largest semidiurnal (M 2 ) and diurnal (K 1 ) components; results for the second-largest semidiurnal (S 2 ) and diurnal (O 1 ) IT are gathered in the Appendix of the paper.
Mean values over the global ocean are close for the four models EGBERT, ZHAO, ZARON and RAY, with the two last ones showing a slightly better performance than others. One should note that those J2 results might be biased in favor of the empirical models, as J2 data are used in all of them except for the DUSHAW model (see Table  1 ). To check these results, similar diagnostics are computed using the C2 altimeter database, as described in Sect. 4. 1, which is an independent database for all models. Validation results are given in Figs. 9 and 10 for C2 SSH crossover differences and C2 SLA, respectively. Validations with the C2 database show similar results as for J2, with a significant variance reduction in the C2 SSH differences and SLA for most models in all IT regions; variance gain patterns are generally similar but more widely spread and stronger in C2 SSH maps compared to J2 par-Ocean Sci.
Results for the different regions are gathered in Fig. 13  and show that all empirical models generally manage to remove an important amount of coherent IT energy for the first https://doi. org/10. 5194/os-17-147-2021 Ocean Sci. , 17, 147-180, 2021 Table  4. Mean variance reduction for the J2 and C2 altimeter databases, within each IT region, when using the different M 2 internal-tide models and compared to the ZERO correction case; variance reduction in altimeter SLA (white lines) and for altimeters crossover differences (italic lines) for each mission, in square centimeters. For each IT region, the maximum variance reduction across the different models is in bold. Figure  11. Maps of SSH variance differences at crossovers using either the K 1 IT correction from each model or a reference ZERO correction in the SSH calculation for the J2 and C2 missions (cm 2 ).
The gain is weak but noticeable in the NATL, NPAC, Luzon and Madagascar regions, but the local rise of energy in some regions also indicates that the hydrodynamic model still has some uncertainties, particularly in the Gulf of Guinea region and for short IT scales in the Madagascar region. Recently updated Jason-2 and CryoSat-2 altimeter databases have been used to validate these new models of coherent internal tides over the global ocean, focusing on the four main IT frequencies: M 2 , K 1 , O 1 and S 2. First, the analysis shows clearly the value of using such a complete altimeter database to validate IT models. The great quality of the https://doi. org/10. 5194/os-17-147-2021 Ocean Sci. , 17, 147-180, 2021 The results point to a significant altimeter variance reduction when using the new IT correction models over all ocean regions where internal tides are generated and propagating.
, 2020)  that accounts for the short duration of the time series used in the analysis slightly improves the performance of the HYCOM hydrodynamic solution. Ongoing work is testing whether operational HYCOM simulations, which assimilate altimeter measurements of mesoscale eddies and improve the underlying stratification relative to observations (e. g. ,  Luecke et al. , 2017) , will yield improvements in the skill of the predicted internal tides in HYCOM. The results described here and for which we provide a scientific justification, have been also presented at the last OSTST (Ocean Surface Topography Science Team) meetings of Ponta Delgada Miguel (2018; program available at https://meetings. aviso. altimetry. fr/ programs/2018-ostst-complete-program. html, last access: 18 January 2021) and Chicago (2019; program available at https://meetings.
aviso. altimetry. fr/programs/ 2019-ostst-complete-program. html, last access: 18 January 2021): in the light of these findings, the recommendation came to use an internal-tide model for the correction of all along-track nadir altimeter databases as well as the upcoming high-resolution SWOT wide-swath altimeter mission. Consequently, the ZARON model is being implemented in the next version of the altimeter GDRs (GDR-F-standard: https://www. aviso. altimetry. fr/en/data/, last access: 17 December 2020), which will be available on AVISO. In addition, the impact of using the ZARON IT correction has also been estimated for the level-4 (L4) altimeter products, which are global gridded data. A significant improvement was detected in all the regions of interest, and it was demonstrated that this new correction reduces the remaining IT signal in the L4 AVISO/CMEMS (Copernicus Marine Environment Monitoring Service) products  (Faugère et al.