This had been spurred in part by the recent availability of exceptionally powerful computers. Noteworthy in this respect is the Earth Simulator in Yokohama, Japan, which commenced operations in and provides a peak performance of 40 Terraflops, but competitive supercomputers for scientific applications are now becoming available in the USA and Europe as well. There has developed in the last few years an increased understanding of the scientific value of results from very high resolution comprehensive numerical simulations.
This book documents the first international meeting focused specifically on high-resolution atmospheric and oceanic modeling held at the Earth Simulator Center. Rather than producing a standard conference proceedings it includes papers written by invited speakers at the meeting reporting on their most exciting recent results involving high resolution modeling. Kevin Hamilton , Wataru Ohfuchi. There is a cyclonic circulation with a downcoast coastal current during the nonsummer months and an upcoast current in July.
The period of the upcoast circulation shortens toward the east Figures 3 and This causes the period of upcoast current in the LATEX shelf in model results to be restricted to around 15 days per year, during July, compared with observations that reported a reversal of 2 months [ Nowlin et al.
The relatively small difference in wind direction is critical in the development of the upcoast current, being shorter and weaker in the simulation Figure 3 than in observations. This is because for most of the year the ACWSC has larger values in the north than in the south, with the gradients being more intense during fall and winter Figure A consequence is that there is a net export of water from the western shelf into the deep ocean. The rivers' discharge has a small contribution to the volume balance. The transports in the inner and intermediate shelf are around 0.
Other rivers have a smaller contribution. A region with strong convergence is the southern Texas shelf, between sections C and D, particularly from April to August. Cochrane and Kelly  identified this convergence region, and a later study based on an optimally interpolated wind field derived from buoy data made a detailed description of the ACWSC and the convergence [ Nowlin et al. In this region, events of offshore currents can be identified through remote sensing since the entrained coastal water is cold with high chlorophyll concentration.
The seasonality of the monthly mean upper ocean chlorophyll a content for the period to from the SeaWiFS is consistent with these results Figure The location of the eddies may determine if the offshore current crosses the shelf break or turns cyclonically onto the outer shelf. A second region of strong convergence is in the southernmost part of the Bay of Campeche, between sections I and J, most evident from September to February. A maximum in the chlorophyll a content detected through SeaWiFS data during the fall and winter supports model results that suggest that the offshore transport is more intense during this period Figure The high content of chlorophyll a during fall and winter in the Bay of Campeche does not seem to be produced by coastal upwelling due to Ekman transport since the northerly winter winds are downwelling favorable for the western side of the Bay and neutral for the southern.
Although the winds are upwelling favorable for the eastern side of the Bay of Campeche, they are not significantly more favorable than in the summer. Model temperatures have a good agreement with observations Figures 6 and For the LATEX shelf, the agreement for the November sea surface temperature is within one standard deviation from the observations reported by Nowlin et al.
The offshore Ekman component can be distinguished in the mean surface currents Figure 3. Its seasonal range, measured as the maximum minus the minimum values, is larger at the coast than at the outer shelf, the shelf break, or the slope.
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These results show that the coastal currents within the shelf and the atmospheric sea level pressure are the major contributors to the seasonal sea level signal rather than a western boundary current as was proposed by Sturges and Blaha  , Blaha and Sturges  , and Sturges . However, although weaker, there is a seasonal signal at the slope that may be generated by a western boundary current as Sturges and Blaha suggested, but the causes of the SSH variability at the slope are not analyzed here.
The peak of SSH is associated with the transition between upcoast to downcoast current and the displacement of the regions of stronger convergence. Since the SSH in Galveston leads by one month the peak on the locations downcoast, in model and tide gauges, it seems that the transition is not simultaneous but since the model is forced with monthly winds that cannot be definitively concluded. Nowlin et al. In these sections the gradients point inshore from September to April and offshore from April to July.
Over the western Campeche Bank the gradients are always offshore, being stronger in July and weaker in October—November. In the section at On the LATEX shelf, most of the year there is a cyclonic circulation, with a strong coastal current along the inner shelf and a weaker broad current over the outer shelf. The results from the model simulations show a stronger outer shelf current in April and May when there is a convergence in the southern Texas shelf that feeds the current. Its pattern is similar to the local ocean circulation throughout the year.
The correlation between the ACWSC and the along shore surface currents is high over most of the shelf, except for the convergence zones, supporting the hypothesis that the local wind stress is the main forcing mechanism of the western shelf of the GoM. The cause of the confluence of the shelf currents is the convergence of the ACWSC, due to the combination of the concave shape of the western gulf and the wind direction.
The main consequence of the confluence is the generation of offshore currents, which are notorious in satellite images because these currents are often associated with waters of high chlorophyll a content and contrasting temperature.
Although it has been observed that offshore currents are associated with episodic processes, here it is found that these events have a seasonal modulation. Juan I. We thank Alex Lee for his contributions to the analysis of the sea level data.get link
Numerical modeling, predictability and data assimilation in weather, ocean and climate - CINFAI
Volume , Issue C If you do not receive an email within 10 minutes, your email address may not be registered, and you may need to create a new Wiley Online Library account. If the address matches an existing account you will receive an email with instructions to retrieve your username. Open access. Journal of Geophysical Research: Oceans.
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Search for more papers by this author. Steven L. James J. Tools Request permission Export citation Add to favorites Track citation. Share Give access Share full text access. Share full text access. Please review our Terms and Conditions of Use and check box below to share full-text version of article. Figure 1 Open in figure viewer PowerPoint.
Location of the western Gulf of Mexico and sites of interest. Sections where detailed analysis is presented are indicated with capital letters, and circles indicate the sites stations of surface currents in Figure Figure 2 Open in figure viewer PowerPoint. Thick lines indicate the transports between the coast and the 25 m isobath from surface to bottom. Thin lines indicate the transports between the 25 m and 50 m isobaths. Positive values indicate upcoast transports.
Figure 3 Open in figure viewer PowerPoint. Monthly mean surface currents from 7 years of model data along the western shelf of the Gulf of Mexico. Shown are the isobaths of 25, 50, and m. Figure 4 Open in figure viewer PowerPoint.
Mean surface salinity from the model output for: a May to August and b October to February. Vectors represent the main currents for the period with the same scale as in Figure 3. Shown are the m and m isobaths. Figure 5 Open in figure viewer PowerPoint. Individual temperature and salinity observations from historical hydrographic data. Temperature from May to August a at 5 m depth and b at 30 m depth. Salinity at 10 m depth c from October to March and d from May to August.
Figure 6 Open in figure viewer PowerPoint.
Note the presence of cold water along the western shelf. The m and m isobaths are shown. Figure 7 Open in figure viewer PowerPoint. Monthly mean vertical structure from model output in section E of Figure 1 , averaged from top October to February and bottom May to August of 1 year.
Figure 8 Open in figure viewer PowerPoint. Standard deviations of model data are less than 1 cm. Figure 9 Open in figure viewer PowerPoint.
Atmospheric Extratropical Dynamics
Percentage of the monthly mean sea level variance explained by the model white bars and by the model with the inverse barometer contribution black bars for Galveston Gal , Cd. Figure 10 Open in figure viewer PowerPoint. Positive values indicate downcoast direction. Figure 11 Open in figure viewer PowerPoint.
The values of the correlation coefficients are also indicated in each plot. Error bars represent one standard deviation.
High Resolution Numerical Modelling of the Atmosphere And Ocean
Positive values indicate downcoast currents and wind stress. Figure 12 Open in figure viewer PowerPoint. Monthly means for January—April from to , May—October from to , and November—December from to Figure 13 Open in figure viewer PowerPoint. Bathymetry contour lines of 25, 50, , and m are shown.