Dynamics of baroclinic jets on extrasolar planets is studied using three-dimensional general circulation models (GCMs) which solve the traditional hydrostatic primitive equations. The focus is on: i ) baroclinic ow and instability on hot-Jupiters; ii ) detailed GCM intercomparison in a commonly used extrasolar planet setup; and, iii ) equatorial superrotation on Earth-like planets. Stability, non-linear evolution and equilibration of high-speed ageostrophic jets are studied under adiabatic condition relevant to hot-Jupiters. It is found that zonal jets can be baroclinically unstable, despite the planetary size of the Rossby deformation scale, and that high resolution is necessary to capture the process. Non-linear jet evolution is then used as a test case to assess model convergence in ve GCMs used in current hot-Jupiter simulations. The GCMs are also tested under a diabatic condition (thermal relaxation on a short timescale) similar to that used in many hot-Jupiter studies. In the latter case, in particular, the models show signi cant inter- and intra-model variability, limiting their quantitative prediction capability. Some models severely violate global angular momentum conservation. The generation of equatorial superrotation in Earth-like atmospheres, subject to \Held & Suarez-like" zonally-symmetric thermal forcing is also studied. It is shown that transition to superrotation occurs when the meridional gradient of the equilibrium surface entropy is weak in this setup. Two factors contribute to the onset of superrotation | suppression of breaking Rossby waves (generated by midlatitude baroclinic instability) that decelerate the equatorial ow, and, generation of inertial and barotropic instabilities in the equatorial region that provide the stirring to accelerate the equatorial ow. In summary, forcing condition and physical setup used in current hot-Jupiter simulations severely stretch model performance and predictive capability. Superrotation in Earth-like conditions may be common, but its strength decreases with resolution. Broadly, numerical convergence must be assessed in GCM experiments for each problem or setup considered.

This study investigates the hydrodynamic variations along the Gao-ping Submarine Canyon influence by the topography effects. The data used in this study were collected from two cruises of field observations using research vessel OR3. Instruments applied include sb-ADCP¡Bbm-ADCP¡Bmoored-ADCP¡BCTD and several vertical strings of temperature loggers. Parameters recorded include flow velocities, water temperature and tidal elevation. The analysis method is enlightenment by the case study in the Monterey Canyon of California. The results show that (1) the current speed in the lower layer is faster than that of upper layer, which is explained due to v-shape of topography and bottom-trapped effect of internal tide. This result is consistent with previous studies. (2) In flood tide, the currents flowed into the Canyon from deep water to shallower. The baroclinic kinetic energy decreased to 0.2 at the turning point of canyon axis at 230m water, whichwas caused mainly by bottom friction. On the other hand, the baroclinic kinetic energy increased to 0.47 at 250m water in ebb tide when there was less influence of bottom friction. (3) In comparison the effects of bottom slope and area of cross section of the canyon, the baroclinic kinetic energy dissipation was mainly occurred at up slope flow during the flood tide. The change of the canyon width had less influence. During the ebb, the baroclinic kinetic energy was mainly due to the change of canyon width in the region shallower then the 230m of the second turning of the canyon. (4) The loss of kinetic energy during flooding up slope current can be verified by the changes of water mass temperature. Cold bottom was raised to upper layer when there was large drop of kinetic energy. There was likely a conversion of kinetic energy to potential energy. No upwelled cold water detected during ebb current with increase of kinetic energy.

The dissertation first investigates gravity wave generation and propagation from jets within idealized vortex dipoles using a nonhydrostatic mesoscale model. Several initially balanced and localized jets induced by vortex dipoles are examined here. Within these dipoles, inertia-gravity waves with intrinsic frequencies 1-2 times the Coriolis parameter are simulated in the jet exit region. The ray tracing analysis reveals strong variation of wave characteristics along ray paths. The dependence of wave amplitude on the Rossby number is examined through experiments in which the two vortices are initially separated by a large distance but subsequently approach each other and form a vortex dipole with an associated amplifying localized jet. The amplitude of stationary gravity waves in the simulations with a 90-km grid spacing increases nearly linearly with the square of the Rossby number but significantly more rapidly when smaller grid spacing is used. To further address the source mechanism of the gravity waves within the vortex dipole, a linear numerical framework is developed based on the framework proposed by Plougonven and Zhang (2007). Using the nonlinearly balanced fields as the basic state and driven by three types of large scale forcing, the vorticity, divergence and thermodynamic forcing, this linear model is utilized to obtain linear wave responses. The wave packets in the linear responses compare reasonably well with the MM5 simulated gravity waves. It is suggested that the vorticity forcing is the leading contribution to both gravity waves in the jet exit region and the ascent/descent feature in the jet core. This linear model is also adopted to study inertia-gravity waves in the vicinity of a baroclinic jet during the life cycle of an idealized baroclinic wave. It is found that the thermodynamic forcing and the vorticity forcing are equally important to the gravity waves in the low stratosphere, but the divergence forcing is again playing a lesser role. Two groups of wave packets are present in the linear responses; their sources appear to locate either near the surface front or near the middle/upper tropospheric jet.

No description available.

Thesis (M.S.)--Florida State University, 2005. / Advisor: Dr. Philip Cunningham, Florida State University, College of Arts and Sciences, Dept. of Meteorology. Title and description from dissertation home page (viewed June 7, 2005). Document formatted into pages; contains xiv, 118 pages. Includes bibliographical references.

Thesis (Ph. D.)--Massachusetts Institute of Technology, 1984. / Includes bibliographical references (p. 127-135).

Thesis (Ph. D.)--Texas A & M University, 1992. / Vita. Includes bibliographical references (leaves 101-102).

No description available.

Finite difference numerical models based upon the Navier-Stokes equations with the Boussinesq approximation have been utilized to study the dynamics of a rotating liquid with horizontal density gradients. There are two configurations analyzed: a cylindrical annulus of water rotating about a vertical axis (parallel to the body force), and a hemispherical shell of silicone oil with a radial body force, rotating about the polar axis. In both the cylindrical and spherical configurations, the thermal and mechanical forcings (boundary conditions) are symmetric about the axis of rotation. The physical parameters varied are the rotation rate and the amplitude of the horizontal thermal forcing. Two numerical models have been developed for each geometrical configuration: one to calculate axisymmetric flows and another to test the stability of those flows to non-axisymmetric perturbations. The primary purpose of the models is to determine whether axisymmetric or non-axisymmetric flow will be observed in a corresponding laboratory experiment. For the cylindrical annulus, the predictions of axisymmetric and non-axisymmetric flow are in good agreement with laboratory experiments previously performed. In the spherical experiment considered, which has not been performed in the laboratory, there is evidence that if the rotation rate is fixed and the latitudinal thermal forcing is reduced, there exists a transition from non-axisymmetric to axisymmetric flow, but that as the rotation rate is decreased for a fixed latitudinal thermal gradient on the boundaries, the flow does not become axisymmetric. The structures of some of the fastest growing eigenmodes are presented for both cylindrical and spherical cases. Analyses of the energetics indicate that the waves in all cases considered are essentially baroclinic in nature.

As pointed out by Farrell, a normalmode analysis alone may be not enough for a convicing investigation of baroclinic stability. In some models growth rates can be achieved large enough to enable nonlinear growth also in parameter ranges of neutral normalmodes. According to Farrell one has also to consider that structures, which achieve optimal growth for a given, fixed time interval (i.e. the singular vectors). Fischer (1998) investigated this problem for the classical Eady-model with q' = 0 - a case which can be treated analytically. In this paper we want to give a short overview of an investigation of singular vectors in Eady-models with β ≠ 0 and q' = 0. Our aim was to understand the influence of β ≠ 0 on optimal growth. Qualitative differences to Fischer’s results are only found at small wavenumbers below the longwave cutoff. The most remarkable difference beyond the longwave cutoff is the fact, that the singular vectors of the model with β ≠ 0 grow faster in the upper half of the fluid than in the lower half for the considered basic flows. The growth rates for parameter ranges of neutral normalmodes are too small to enable nonlinear growth effects in meteorologically relevant times. For long timescales we find, that the cutoffs must be understood more as a smooth transition to instability.