Professor Giorgio Passerini from the University of Ancona visited WIT recently and delivered a lecture on "Circulation Models in Coastal Valleys" in which he discussed a range of models suitable for these regions and the best way to introduce the complex topography of the area.
Coastal regions have particular characteristics, which are difficult to model and special atmospheric effects need to be taken into consideration.
Giorgio referred, in particular, to a region of Italy called the Esino Valley, which includes the town of Ancona. There exists the largest refinery in Europe in addition to major motorways. Before attempting to model the zone using computer simulation, a series of tests were carried out in the proximity of Ancona to determine the extent of the air pollution.
It was decided to apply a numerical weather model with sufficiently high horizontal and vertical resolution to forecast mesoscale weather phenomena (such as the well know MM5 and RAMS models). They allow for varying horizontal resolution and spacing typically of less than 30kms.
These circulation models are able to provide detailed analysis and accordingly to represent the intensity of small-scale weather phenomena provided that the vertical resolution is represented properly.
The Esino Valley region is a particularly interesting case study, due to its complex topography and to the presence of the city of Ancona. The Valley is surrounded by hillsides sharply rising to mountain height, which renders the shape of the valley very complex. The region also experiences coastal breezes produced by the different heating ratios of land and sea.
The RAMS software used in the study can analyse all these processes using a multiple grid nested system such that a coarse grid can define the boundary conditions and a finer grid to model more accurately the region of interest. RAMS can accept Meteorological data as well as topographical information. The sea surface temperature, an important parameter for these simulations can also be given. The model presents the output in graphical form and can give prognostic simulations to study the effect of a variety of different conditions.
Giorgio presented a series of applications in the Esino Valley, demonstrating how the model behaves in terms of precision and accuracy of the results. As a conclusion, the introduction of high resolution terrain data in the model has been shown to increase the accuracy of atmospheric dynamic simulation. This enhancement is more important in coastline areas where temperature and humidity gradients can trigger unique types of breeze phenomena.
Wessex Institute