Mesoscale to LES Framework to Study Atmospheric Flows over Complex Island Terrain

LES are often used to study boundary layer turbulence and solve local wind/eddies phenomena in a much-detailed manner relatively to mesoscale models. Larger turbulent eddies are explicitly solved while the effects of smaller ones are parameterized. The principal objective of this study is to assess the capability of the Weather Research and Forecast Large Eddy Simulation (WRF-LES) framework, forced by mesoscale models for resolving the atmospheric flow within Madeira island complex orography. The first consideration was to implement very detailed topography (SRTM) and Land Use (CLC) data into the model, using high grid-resolution local domains (333, 200 and 100 m). A sensitivity study used different boundary conditions (CFSv2, ERA5, FNL and MERRA2) and two different domain configurations. Results shows that although the Kármán vortex streets are well replicated by the mesoscale systems, local phenomena such as an hydraulic jump that forms leeward of a mountain and the sea-mountain breezes, which develop between the daily thermal cycles, are better represented using LES. Nevertheless, the introduction of high-resolution Sea Surface Temperature fields from a regional ocean circulation model calculation did not show significant improvements, relatively to using the global satellite datasets. Comparing model with in-situ data, LES shows a better performance relatively to its mesoscale counterparts.