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Non-hydrostatic Modeling of Exchange Flows Across Complex Geometries
Flows between ocean and marginal sea basins are often connected by narrow channels and shallow sills. In this study, we address the effect of lateral and vertical geometric constrictions on mixing and hydraulic control. We conduct a set of numerical experiments of the lock-exchange problem in the presence of lateral and vertical contractions. Large eddy simulations (LES) are carried out using the high-order non-hydrostatic spectral element model Nek5000. A spanwise-averaged 2D non-hydrostatic model, denoted SAM, is also employed. Comparison between 2D and 3D models are conducted on the basis of the shape of the density interface and the time evolution of the background potential energy that quantifies the cumulative effects of the stratified mixing in the system
Interactive dust-radiation modeling: A step to improve weather forecasts
[ 1] Inclusion of mineral dust radiative effects could lead to a significant improvement in the radiation balance of numerical weather prediction models with subsequent improvements in the weather forecast itself. In this study the radiative effects of mineral dust have been fully incorporated into a regional atmospheric dust model. Dust affects the radiative fluxes at the surface and the top of the atmosphere and the temperature profiles at every model time step when the radiation module is processed. These changes influence the atmospheric dynamics, moisture physics, and near-surface conditions. Furthermore, dust emission is modified by changes in friction velocity and turbulent exchange coefficients; dust turbulent mixing, transport, and deposition are altered by changes in atmospheric stability, precipitation conditions, and free-atmosphere winds. A major dust outbreak with dust optical depths reaching 3.5 at 550 nm over the Mediterranean region on April 2002 is selected to assess the radiative dust effects on the atmosphere at a regional level. A strong dust negative feedback upon dust emission ( 35-45% reduction of the AOD) resulted from the smaller outgoing sensible turbulent heat flux decreasing the turbulent momentum transfer from the atmosphere and consequently dust emission. Significant improvements of the atmospheric temperature and mean sea-level pressure forecasts are obtained over dust-affected areas by considerably reducing both warm and cold temperature biases existing in the model without dust-radiation interactions. This study demonstrates that the use of the proposed model with integrated dust and atmospheric radiation represents a promising approach for further improvements in numerical weather prediction practice and radiative impact assessment over dust-affected areas