Vérification expérimentale de la mesure de la dérive de Stokes par les radars hautes-fréquences
Bibliographic record
Abstract
RÉSUMÉ: Les radars hautes-fréquences (HF) mesurent les courants à la surface de l'océan, en émettant des ondes électromagnétiques (EM) dans la bande radio HF (3-30 MHz) et en enregistrant les ondes EM rétrodiffusées par les ondes de gravité de surface. Le signal enregistré est dominé par les ondes EM rétrodiffusées par les ondes de gravité de surface ayant une longueur d'onde égale à la moitié de la longueur d'onde EM émise, appelées vagues de Bragg. Leur vitesse de phase est affectée par une interaction avec les courants Eulériens moyens, et aussi en principe avec toutes les autres vagues présentes à la surface de la mer. Cependant, la littérature est incohérente sur l'expression et même sur l'existence de la contribution de la dérive de Stokes, induite par les vagues, aux mesures radar. Trois expressions différentes ont été proposées dans la littérature : (1) la dérive de Stokes en surface filtrée, (2) la moitié de la dérive de Stokes en surface et (3) la dérive de Stokes moyenne pondérée en profondeur. Nous évaluons ces expressions pour les spectres de vagues directionnels mesurés par trois profileurs acoustiques de vague et de courant (AWAC) mouillés dans l'estuaire maritime du Saint-Laurent, au Canada. Nous comparons ensuite les courants de surface Eulériens mesurés par les AWACs avec les courants radiaux mesurés par quatre radars HF : deux radars de type WERA (WEllen RAdar) et deux radars de type CODAR (Coastal Ocean Dynamics Applications Radars). Étonnamment, les courants des radars HF et des AWACs ne sont presque pas corrélés, mais en soustrayant les contributions associées à la dérive de Stokes des mesures radar, on obtient des corrélations modérées, mais significatives. Les corrélations les plus élevées sont obtenues en soustrayant la dérive de Stokes de surface filtrée, ce qui suggère que les radars HF mesurent cette dernière en plus des courants Eulériens moyens. -- Mot(s) clé(s) en français : Radars Hautes-Fréquences, Dérive de Stokes, Courants de surface. -- ABSTRACT: High frequency (HF) radars measure ocean surface currents by sending electromagnetic (EM) waves in the HF radio band (3-30 MHz) and recording the EM waves backscattered by ocean surface gravity waves. The recorded signal is dominated by EM waves backscattered from ocean surface waves with half the EM wavelength, called Bragg waves. Since their phase velocity is affected not only by wave-current interactions with mean Eulerian currents, but also by wave-wave interactions with all the other waves present at the sea surface, the question arises as to whether HF radars measure a quantity related to the wave-induced Stokes drift in addition to mean Eulerian currents. However, the literature is inconsistent on the expression and even on the existence of the contribution of the wave-induced Stokes drift to the HF radar measurements. Three different expressions have been proposed in the literature: (1) the filtered surface Stokes drift, (2) half of the surface Stokes drift, and (3) the weighted depth-averaged Stokes drift. We evaluate these expressions for directional wave spectra measured by three bottom-mounted Acoustic Wave and Current (AWAC) profilers in the Lower St. Lawrence estuary, Canada. We then compare the Eulerian surface currents measured by the AWACs with the radial currents measured by four HF radars: two Wellen Radars (WERA) and two Coastal Ocean Dynamics Applications Radars (CODAR). The AWAC and HF-radar currents are surprisingly almost not correlated, but when subtracting the wave-induced Stokes drift contributions from the radar measurements, moderate but significant correlations are obtained. The highest correlations are obtained when subtracting the filtered surface Stokes drift, suggesting that HF radars measure the latter in addition to mean Eulerian currents. -- Mot(s) clé(s) en anglais : High-Frequency radars, Stokes drift, surface currents.
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How this classification was reachedexpand
Full frame distilled prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. Learned from the 10,348 direct Codex labels and 10,348 direct Gemma labels. Candidate is the union of thresholded teacher heads; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels or direct frontier model labels.
Codex and Gemma teacher scores by category
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.001 | 0.000 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.000 | 0.000 |
| Science and technology studies | 0.001 | 0.001 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.001 | 0.000 |
| Research integrity | 0.000 | 0.001 |
| Insufficient payload (model declined to judge) | 0.002 | 0.000 |
Machine scores (provisional)
The two teacher heads of the student model, read on this work. A score orders the frame for review; it never asserts a category, and the validation status ships verbatim with every row.
Baseline scores from an immature model (maturity gate not passed, 7 training rounds). Scores rank; they never assert a category.
score_only:v0-immature-baseline · verbatim from the scoring run: score_only means the number may rank works, and no category label ships from itClassification
machine, unvalidatedMachine predicted; a candidate call from one teacher head, not a consensus.
How this classification was reached, model by model and score by score, is at the end of the page under "How this classification was reached".