Andy Hogg: Models

This page contains a number of numerical codes and algorithms which are freely available to all academic users.

Q-GCM: "Quasi-Geostrophic Coupled Model"

Q-GCM is a "Quasi-Geostrophic Coupled Model" which has been developed in collaboration with Jeff Blundell, Bill Dewar and Peter Killworth.

This idealised midlatitude ocean-atmosphere model is designed to investigate how instabilities in the wind-driven ocean circulation may produce climate variability in the midlatitudes.

The image on the right shows atmospheric pressure contours (red) overlaying the high-resolution Sea Surface Temperature field from the Southern Ocean version of Q-GCM.

In addition the model will be used to look at midlatitude coupled modes and propagation of Rossby waves in coupled systems.

Code is freely available from the Q-GCM Homepage.

Time-dependent Hydraulic Models

The dynamics of flow through ocean straits is well described by internal hydraulic theory. A relevant extension to standard hydraulic theory is time-dependent hydraulics, which has been investigated using two simple models. These models solve the one-dimensional one-layer shallow water equations, or the two-layer shallow water equations as shown in the maximal exchange example on the left. The models are used in the following publications:

J. NYCANDER, A. McC. HOGG & L. M. FRANKCOMBE, (2008). Open boundary conditions for nonlinear shallow water models. Ocean Mod., doi:10.1016/j.ocemod.2008.06.003. [Online copy from OM]

L. M. FRANKCOMBE & A. McC. HOGG, (2007). Tidal modulation of two-layer hydraulic exchange flows. Ocean Science, 3, 179-188. [On-line copy from OS]

Downloads

The code is freely available for download via the links below. The latest version is v2.0 (30th April 2008) which includes both the one- and two-layer versions in the one code. The download is a tar file format -- instructions can be found once the package is untarred.

DOWNLOAD onedee_v2.0

There are also older versions of this code which separate the one- and two-layer cases:

DOWNLOAD onedee_unilayer_v1.3

DOWNLOAD onedee_bilayer_v1.5

Sixth-Order Eigenvalue Solver

WAVDIF is a fortran code to solve for the viscous sixth order wave equation, expressed as:

This code can be used, for example, to solve for stability of a stratified shear flow, incorporating the effects of viscocsity. The image on the right shows a comparison of Kelvin-Helmholtz and Holmboe instability properties (a) without and (b) with viscosity. The red dots show the transition from KH to Holmboe, with KE active at low Richardson number.

This code is co-written by Kraig Winters, and is used in the following papers:

A. McC. HOGG & G. N. IVEY, (2003). The Kelvin-Helmholtz to Holmboe instability transition in stratified exchange flows. J. Fluid. Mech. 477, 339-362. [On-line Copy from JFM]

L. BOEGMAN, J. IMBERGER, G.N. IVEY & J.P. ANTENUCCI, (2003) High-frequency internal waves in large stratified lakes. Limnol. Oceanogr. 48, 895-919.

A. McC. HOGG, K. B. WINTERS & G. N. IVEY, (2001). Linear Internal waves and the control of stratified exchange flows. J. Fluid. Mech., 447, 357-375. [On-line Copy from JFM]

Downloads

The code is freely available for download via the links below. The latest version is v3.1. The download is a gzipped tar file format -- instructions can be found once the package is untarred.

DOWNLOAD wavdif_v3.1

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