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You searched for +publisher:"University of St. Andrews" +contributor:("Reinaud, Jean Noel"). Showing records 1 – 2 of 2 total matches.

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University of St. Andrews

1. Devlin, David J. J. An investigation into the use of balance in operational numerical weather prediction .

Degree: 2011, University of St. Andrews

Presented in this study is a wide-ranging investigation into the use of properties of balance in an operational numerical weather prediction context. Initially, a joint numerical and observational study is undertaken. We used the Unified Model (UM), the suite of atmospheric and oceanic prediction software used at the UK Met Office (UKMO), to locate symmetric instabilities (SIs), an indicator of imbalanced motion. These are areas of negative Ertel potential vorticity (in the Northern hemisphere) calculated on surfaces of constant potential temperature. Once located, the SIs were compared with satellite and aircraft observational data. As a full three-dimensional calculation of Ertel PV proved outwith the scope of this study we calculated the two-dimensional, vertical component of the absolute vorticity, to assess the inertial stability criterion. We found that at the synoptic scale in the atmosphere, if there existed a symmetric instability, it was dominated by an inertial instability. With the appropriate observational data, evidence of inertial instability from the vertical component of the absolute vorticity, predicted by the UM was found at 12km horizontal grid resolution. Varying the horizontal grid resolution allowed the estimation of a grid length scale, above which, the inertial instability was not captured by the observational data, of approximately 20km. Independently, aircraft data was used to estimate that horizontal grid resolutions above 20-25km should not model any features of imbalance providing a real world estimate of the lower bound of the grid resolution that should be employed by a balanced atmospheric prediction model. A further investigation of the UM concluded that the data assimilation scheme and time of initialisation had no effect on the generation of SIs. An investigation was then made into the robustness of balanced models in the shallow water context, employing the contour-advective semi-Lagrangian (CASL) algorithm, Dritschel & Ambaum (1997), a novel numerical algorithm that exploits the underlying balance observed within a geophysical flow at leading order. Initially two algorithms were considered, which differed by the prognostic variables employed. Each algorithm had their three-time-level semi-implicit time integration scheme de-centred to mirror the time integration scheme of the UM. We found that the version with potential vorticity (PV), divergence and acceleration divergence, CA[subscript(δ,γ)], as prognostic variables preserved the Bolin-Charney balance to a much greater degree than the model with PV, divergence and depth anomaly CA[subscript(tilde{h},δ)], as prognostic variables. This demonstrated that CA[subscript(δ,γ)] was better equipped to benefit from de-centring, an essential property of any operational numerical weather prediction (NWP) model. We then investigate the robustness of CA[subscript(δ,γ)] by simulating flows with Rossby and Froude number O(1), to find the operational limits… Advisors/Committee Members: Reinaud, Jean Noel (advisor), Cullen, Mike J. P (advisor).

Subjects/Keywords: Balance; NWP; CASL; Shallow water; Non-hydrostatic; Unified Model

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APA · Chicago · MLA · Vancouver · CSE | Export to Zotero / EndNote / Reference Manager

APA (6th Edition):

Devlin, D. J. J. (2011). An investigation into the use of balance in operational numerical weather prediction . (Thesis). University of St. Andrews. Retrieved from http://hdl.handle.net/10023/1903

Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation

Chicago Manual of Style (16th Edition):

Devlin, David J J. “An investigation into the use of balance in operational numerical weather prediction .” 2011. Thesis, University of St. Andrews. Accessed June 17, 2019. http://hdl.handle.net/10023/1903.

Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation

MLA Handbook (7th Edition):

Devlin, David J J. “An investigation into the use of balance in operational numerical weather prediction .” 2011. Web. 17 Jun 2019.

Vancouver:

Devlin DJJ. An investigation into the use of balance in operational numerical weather prediction . [Internet] [Thesis]. University of St. Andrews; 2011. [cited 2019 Jun 17]. Available from: http://hdl.handle.net/10023/1903.

Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation

Council of Science Editors:

Devlin DJJ. An investigation into the use of balance in operational numerical weather prediction . [Thesis]. University of St. Andrews; 2011. Available from: http://hdl.handle.net/10023/1903

Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation


University of St. Andrews

2. Bambrey, Ross R. Strong interaction between two co-rotating vortices in rotating and stratified flows.

Degree: 2007, University of St. Andrews

In this study we investigate the interactions between two co-rotating vortices. These vortices are subject to rapid rotation and stable stratification such as are found in planetary atmospheres and oceans. By conducting a large number of simulations of vortex interactions, we intend to provide an overview of the interactions that could occur in geophysical turbulence. We consider a wide parameter space covering the vortices height-to-width aspect-ratios, their volume ratios and the vertical offset between them. The vortices are initially separated in the horizontal so that they reside at an estimated margin of stability. The vortices are then allowed to evolve for a period of approximately 20 vortex revolutions. We find that the most commonly observed interaction under the quasi-geostrophic (QG) regime is partial-merger, where only part of the smaller vortex is incorporated into the larger, stronger vortex. On the other hand, a large number of filamentary and small scale structures are generated during the interaction. We find that, despite the proliferation of small-scale structures, the self-induced vortex energy exhibits a mean `inverse-cascade' to larger scale structures. Interestingly we observe a range of intermediate-scale structures that are preferentially sheared out during the interactions, leaving two vortex populations, one of large-scale vortices and one of small-scale vortices. We take a subset of the parameter space used for the QG study and perform simulations using a non-hydrostatic model. This system, free of the layer-wise two-dimensional constraints and geostrophic balance of the QG model, allows for the generation of inertia-gravity waves and ageostrophic advection. The study of the interactions between two co-rotating, non-hydrostatic vortices is performed over four different Rossby numbers, two positive and two negative, allowing for the comparison of cyclonic and anti-cyclonic interactions. It is found that a greater amount of wave-like activity is generated during the interactions in anticyclonic situations. We also see distinct qualitative differences between the interactions for cyclonic and anti-cyclonic regimes. Advisors/Committee Members: Reinaud, Jean Noel (advisor), Dritschel, David Gerard (advisor).

Subjects/Keywords: Vortex interactions; Geophysical flows; Quasi-geostrophic; Non-hydrostatic; Inertia-gravity waves; Imbalanced flows; Vortex merger; Energy cascades

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APA · Chicago · MLA · Vancouver · CSE | Export to Zotero / EndNote / Reference Manager

APA (6th Edition):

Bambrey, R. R. (2007). Strong interaction between two co-rotating vortices in rotating and stratified flows. (Thesis). University of St. Andrews. Retrieved from http://hdl.handle.net/10023/341

Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation

Chicago Manual of Style (16th Edition):

Bambrey, Ross R. “Strong interaction between two co-rotating vortices in rotating and stratified flows. ” 2007. Thesis, University of St. Andrews. Accessed June 17, 2019. http://hdl.handle.net/10023/341.

Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation

MLA Handbook (7th Edition):

Bambrey, Ross R. “Strong interaction between two co-rotating vortices in rotating and stratified flows. ” 2007. Web. 17 Jun 2019.

Vancouver:

Bambrey RR. Strong interaction between two co-rotating vortices in rotating and stratified flows. [Internet] [Thesis]. University of St. Andrews; 2007. [cited 2019 Jun 17]. Available from: http://hdl.handle.net/10023/341.

Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation

Council of Science Editors:

Bambrey RR. Strong interaction between two co-rotating vortices in rotating and stratified flows. [Thesis]. University of St. Andrews; 2007. Available from: http://hdl.handle.net/10023/341

Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation

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