Mean dynamic topography of the Gulf of Mexico with application to satellite altimetry

Maul, George A.; Herman, Alan

doi:10.1080/15210608509379514

Cited by 12 publications

(5 citation statements)

References 16 publications

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“…The curve of their mean value is similar to the typical annual cycle of height over the whole Gulf that results from seasonal cycle of heating. Figure 2 is similar to the long-term dynamic height results of Maul and Herman (1985), although the WOA18 is based on a much larger dataset. Furthermore, recent results by Lilly and Pérez-Brunius (2021) using a much larger set of drifter data also show a return flow in the northern half of the basin.…”

Section: Introductionsupporting

confidence: 52%

On the non-geostrophic appearance of some mean surface velocity observations in the Gulf of Mexico

Sturges

2021

Journal of Physical Oceanography

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A previous study of currents in the Gulf of Mexico by the author used long-term means from three independent data sources. Ship-drift results are in good agreement with surface drifters, but these two do not agree with satellite sea-surface heights (SSH). The agreement between the first two suggested the possibility that there could be errors in the SSH or that the mean surface flow is not in geostrophic balance. The present results, using the addition of a fourth long-term mean from hydrographic data, which agrees with the SSH, resolves the issue. The lack of agreement between different long-term means is from inadequate coverage in space and time in data from ship drifts and drifters.

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Section: Introductionsupporting

confidence: 52%

On the non-geostrophic appearance of some mean surface velocity observations in the Gulf of Mexico

Sturges

2021

Journal of Physical Oceanography

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“…The regions of observed flow to the west, however, are found in the south and in the north at depths less than ;1000 m, so the desired comparisons are not commonly computed [e.g., the Maul and Herman (1985) dynamic height maps relative to 1000 db]. Molinari et al (1978), in addition to maps relative to 1000 db, computed monthly maps relative to 500 db.…”

Section: Discussionmentioning

confidence: 98%

A Puzzling Disagreement between Observations and Numerical Models in the Central Gulf of Mexico

Sturges

Bozec

2013

Journal of Physical Oceanography

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Two large, independent sets of direct observations in the central Gulf of Mexico show a mean near-surface flow of ;10 cm s 21 to the west, concentrated in the northern and southern Gulf. Numerical models that the authors have examined do not produce this mean westward flow. The observed speeds appear to be almost an order of magnitude larger than the estimated errors; this paper studies the observations to estimate carefully the possible errors involved and compares the observations with model results. The flow to the west in the southern Gulf is presumably wind driven on the shallow parts of the shelf, and, in slightly deeper water at the outer edges of the shelf, is possibly the result of southward Sverdrup interior flow driven by the negative curl of the wind stress. In another possibly related issue, long-term deep current-meter observations in the northern Gulf at ;1000 m and below find flow to the west, whereas some models find flow to the east. The flow proposed here assumes a mean flow to the west above roughly 300 m, with a required return flow in deep water. The difference between the deep observations and the models will produce a slope of pressure surfaces of the opposite sign below 1000 m, reversing the direction of upper-layer geostrophic flow in the models.

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“…

A primitive equation ocean model has been applied to the study of mesoscale ocean dynamics and prediction using sea surface height information derived from a satellite-borne altimeter. Results from a model of the Gulf of Mexico were directly compared with the altimeter data from GEOS 3 and Seasat reported by Marsh et al (1984) and in situ hydrographic data analyzed by Maul and Herman (1985). In the eastern Gulf the amplitude and position of relative maxima of sea surface height variability were found to be similar for model, altimeter, and in situ data.

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mentioning

confidence: 79%

“…Recently, Maul and Herman [1985], henceforth referred to as MH, completed a comprehensive calculation of the mean and standard deviation of the dynamic sea surface topography for the Gulf of Mexico. Using all available hydrographic, STD, and expendable bathythermograph (XBT) data from the national archive and other sources (over 26,000 stations), they calculated dynamic heights at a 25-km resolution using 1000 dbar as the reference level.…”

Section: Gulf Of Mexico Datamentioning

confidence: 99%

“…The paper is arranged as follows: section 2 provides a discussion of the physical oceanography of the Gulf of Mexico, particularly with respect to the mean and the time-variable dynamic height of the sea surface as determined by Maul and Herman [1985] from in situ data and from GEOS 3 and Seasat crossover data analyzed by Marsh et al [1984]. Section 3 offers an outline of the Gulf of Mexico primitive equation model originally developed by tturlburt and Thompson [1980] and extended by Wallcraft to include irregular Gulf geometry [Wallcraft and Thompson, 1984].…”

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confidence: 99%

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Altimeter data and geoid error in mesoscale ocean prediction: Some results from a primitive equation model

Thompson¹

1986

J. Geophys. Res.

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A primitive equation ocean model has been applied to the study of mesoscale ocean dynamics and prediction using sea surface height information derived from a satellite‐borne altimeter. Results from a model of the Gulf of Mexico were directly compared with the altimeter data from GEOS 3 and Seasat reported by Marsh et al. (1984) and in situ hydrographic data analyzed by Maul and Herman (1985). In the eastern Gulf the amplitude and position of relative maxima of sea surface height variability were found to be similar for model, altimeter, and in situ data. In the central Gulf the model and the altimeter‐derived sea surface height variability maps were similar but differed considerably from the in situ results. The mean sea surface in the model and from the in situ data also agreed well in the eastern Gulf, but there was little agreement in the central Gulf. While there is no geoid adequate for determining an independent altimetric estimate of the mean dynamic height of the sea surface in the Gulf by differencing the geoid with the altimeter‐derived mean sea surface, the model dynamic mean sea surface can be subtracted from the mean surface of Marsh et al. (1984) to obtain a new estimate of the Gulf geoid, which may be the best geoid available in that region for several years. A benchmark experiment (“truth”) was integrated to statistical equilibrium and compared with results from four experiments in which the model was initialized with fields modified from archived benchmark data. The experiments differed only in the initialization fields. Each experiment was integrated for 100 days with inflow transport remaining constant throughout the integration. The idealized experiments were initialized geostrophically (1) with the exact sea surface and pycnocline height fields, (2) with only the exact sea surface heights and a pycnocline assumed to compensate it such that the deep pressure perturbations vanished, (3) just as in case 2 but with a geoid error component added on small spatial scales, and (4) just as in case 3 except the geoid error model included an additional contribution in strong geoid gradient regions. The sequence of four numerical experiments showed that (1) geostrophic initialization with exact sea surface and pycnocline height information provided accurate forecasts to 100 days, (2) even when only the sea surface height information was provided to the numerical model for geostrophic initialization and deep pressure perturbations assumed to vanish at the initial time, the forecasts were superior to persistence or climatology over the 100‐day forecast period, and (3) errors in the geoid on spatial scales comparable to the grid resolution of the model did not seriously degrade the forecast, even in dynamically active regions with large gradients in the geoid height where instability processes were observed to occur.

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Mean dynamic topography of the Gulf of Mexico with application to satellite altimetry

Cited by 12 publications

References 16 publications

On the non-geostrophic appearance of some mean surface velocity observations in the Gulf of Mexico

On the non-geostrophic appearance of some mean surface velocity observations in the Gulf of Mexico

A Puzzling Disagreement between Observations and Numerical Models in the Central Gulf of Mexico

Altimeter data and geoid error in mesoscale ocean prediction: Some results from a primitive equation model

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