Browsing by Subject "baroclinic"
Now showing 1 - 3 of 3
Results Per Page
Sort Options
Item Assessing the frictional and baroclinic contributions to stratified wake formation: a parameter space study(Texas A&M University, 2006-08-16) Smith, Jamie BrookeThe baroclinic and surface-frictional contributions to stratified wake formation are considered as a function of the non-dimensional height ( = Nho/U) and aspect-ratio ( = ho/L) of the barrier. Numerical simulations are computed for a wide range of the - parameter space, including both unstratified ( = 0) and highly stratified ( = 4) flows and for terrain slopes characteristic of both geophysical ( = 0.1) and laboratory scale ( = 2.0) obstacles. Simulations both with and without applied surface stresses are compared to gain insight into the baroclinic and surface-frictional contributions to each flow. Particular emphasis is given to the changes in kinematic wake structure, the relative contributions of skin and pressure drag, and the vertical momentum flux observed as the mountain height and terrain slope are varied. We also examine several cases from the parameter-space study in more detail using a method for decomposing the flow into baroclinic and viscous parts. The decompositions show that for large- and small- flows, wake generation is primarily baroclinic in nature, while at smaller- and/or larger-, the wake becomes increasingly surface frictional.Item Effects of baroclinicity on storm divergence and stratiform rain in a precipitating subtropical region(2009-05-15) Hopper, Jr., Larry JohnDivergence structures associated with the spectrum of precipitating systems in the subtropics and midlatitudes are not well documented. A mesoscale model (MM5) is employed to quantify the relative importance different baroclinic environments have on divergence profiles for common storm types in southeast Texas, a subtropical region. Divergence profiles averaged over a 100 x 100 nested grid with 3-km grid spacing are calculated from the model-derived wind fields for each storm. The divergence profiles simulated for selected storms are consistent with those calculated from an S-band radar using the velocity-azimuth display (VAD) technique. Divergence profiles from well-modeled storms vary in magnitude and structure across the spectrum of baroclinicities and storm types common in southeast Texas. Barotropic storms more characteristic of the Tropics generate the most elevated divergence (and thus diabatic heating) structures with the largest magnitudes. As the degree of baroclinicity increases, stratiform area fractions increase while the levels of non-divergence (LNDs) decrease. However, some weakly baroclinic storms contain stratiform area fractions and divergence profiles with magnitudes and LNDs that are similar to barotropic storms, despite having lower tropopause heights and less deep convection. Additional convection forms after the passage of some of the modeled barotropic and weakly baroclinic storms that contain elevated divergence signatures, circumstantially suggesting that heating at upper-levels may cause diabatic feedbacks that help drive regions of persistent convection in the subtropics. Applying a two-dimensional stratiform-convective separation algorithm to MM5 reflectivity data generates realistic stratiform and convective divergence signals. Stratiform regions in barotropic storms contain thicker, more elevated mid-level convergence structures with larger magnitudes than strongly baroclinic storms, while weakly baroclinic storms have LNDs that fall somewhere in between with magnitudes similar to barotropic storms. Divergence profiles within convective regions typically become more elevated as baroclinicity decreases, although variations in magnitude are less coherent. These simulations suggest that MM5 adequately captures mass field perturbations within convective and stratiform regions, the latter of which produces diabatic feedbacks capable of generating additional convection. As a result, future research determining the climatological dynamic response caused by divergence profiles in MM5 may be feasible.Item Extended three-dimensional ADCIRC hydrodynamic model to include baroclinic flow and sediment transport(Texas A&M University, 2004-09-30) Pandoe, Wahyu WidodoThe objective of this research is to identify the circulation patterns of the water and sediment fluxes in coastal and estuarine zones, where the shoaling processes correlate with tide generating flow patterns. The research provides a better understanding of the characteristics of spatial and temporal variability of currents. An important deviation from previous research is the inclusion of the baroclinic term, which becomes very important in density driven flows. The understanding of this process provides a basis for determining how the water circulation three-dimensionally controls the hydrodynamics of the system and ultimately transports the suspended and soluble materials due to combined currents and waves. A three-dimensional circulation model is used to calculate the water circulation. The model is based on the three-dimensional (3D) version of Advanced Circulation (AD-CIRC) Hydrodynamic Model with extending the Sediment Transport module. The model is based on the finite element method on unstructured grids. The output of the hydrody-namic model is used to estimate spatial and temporal advections, dispersions and bottom shear stress for the erosion, suspension, deposition and transport of sediment. The model development includes extending the existing three-dimensional (3D) ADCIRC Model with (1) baroclinic forcing term and (2) transport module of suspended and soluble materials. The transport module covers the erosion, material suspension and deposition processes for both cohesive and non-cohesive type sediments. The inclusion of the baroclinic demonstrates the potential of over or underpredicting the total net transport of suspended cohesive sediment under influence of currents. The model provides less than 6% error of theoretical mass conservation for eroded, suspended and deposited sediment material. The inclusion of the baroclinic term in stratified water demonstrates the prevailing longshore sediment transport. It is shown that the model has an application to the transport of the cohesive sediments from the mouth of the Mississippi River along the north shore of the Gulf of Mexico towards and along the Texas coast. The model is also applicable to determine the design erosion thickness of a cap for isolating contaminated dredged material and to evaluate the appro-priate grain size of cap sediments to minimize the erosion.