Multi-model multi-analysis ensemble weather forecasting on the grid for the South Eastern Mediterranean Region

Weather forecasting is based on the use of numerical weather prediction (NWP) models that are able to perform the necessary calculations that describe/predict the major atmospheric processes. One common problem in weather forecasting derives from the uncertainty related to the chaotic behaviour of the atmosphere. A solution to that problem is to perform in addition to “deterministic” forecasts, “stochastic” forecasts that provide an estimate of the prediction skill. A computationally feasible approach towards this aim is to perform “ensemble forecasts”. Indeed, in the frame of SEE-GRID-SCI EU funded project a Regional scale Multi-model, Multi-analysis ensemble forecasting system (REFS) was built and ported on the Grid infrastructure. REFS is based on the use of four limited area models (namely BOLAM, MM5, ETA, and NMM) that are run using a multitude of initial and boundary conditions over the Mediterranean. This paper presents the tools and procedures followed for developing this application at a production level.     

Gulf Stream evolution through the Straits of Florida: the role of eddies and upwelling near Cuba

Ocean Dynamics - The meandering of the Gulf Stream through the Straits of Florida is associated with eddy activity to the north (along the Florida Keys) and the south (along the Cuban coast). This...     

The role of the West Florida Shelf topography on the Loop Current system variability

Ocean Dynamics - The evolution of the Loop Current (LC) system under the interaction with the complex topography of the Gulf of Mexico (GoM) is examined. Focusing on the eastern GoM, we study the...     

On the processes that influence the transport and fate of Mississippi waters under flooding outflow conditions

The Mississippi River (MR) freshwater outflow is a major circulation forcing mechanism for the Northern Gulf of Mexico. We investigate the transport and fate of the brackish waters under flood conditions. The largest outflow in history (45,000 m³/s in 2011) is compared with the second largest outflow in the last 8 years (41,000 m³/s in 2008). Realistically forced simulations reveal the synergistic effect of enhanced discharge, winds, stratification of ambient shelf waters, and offshore circulation over the transport of plume waters. The strongest impact is attributed to the evolution of the Loop Current (LC) and associated frontal cyclonic eddies and anticyclonic rings, which exhibited distinctly different influence during the two study periods. The northward LC intrusion in the summer of 2011 weakened and blocked the buoyancy-driven downstream (westward) transport of brackish waters. The 2011 flood was thus characterized by upstream (eastward) flow and an extensive coverage of the Mississippi–Alabama–Florida shelf. An immediate response between the LC and the brackish offshore eastward spreading is computed during and after this historic event. The absence of a LC northward intrusion during the 2008 flood, in combination with wind effects, promotes downstream advection of MR waters towards the Louisiana–Texas shelf; large amounts of buoyant waters are also retained near the Delta, subject to local offshore advection under the synergistic action of LC-associated counter-rotating eddies.     

Estimation of surface stress over a forest from sodar measurements and its use to parameterize the stable boundary-layer height

Sodar observations from three nights of the HAPEX-MOBILHY experiment have been used to compute covariances between single measurements of the three velocity components. From these, estimates of a low frequency friction velocityu _* are derived which show better correlation with observed values of the stable boundary layer (SBL) height,h, than directu _*-measurements by an ultrasonic anemometer. On the contrary, interdiurnal variability ofh is better correlated with directu _*-measurements. These findings should be mainly due to the problem of different spectral and spatial representativity of the twou _*-values.