Simulazioni meteorologiche con il modello WRF di un evento d'inquinamento in Valle D'Aosta

This thesis work concerns the study of a pollutants dispersion event in Aosta Valley through the use of WRF model at high resolution. Such resolution is necessary to more accurately represent both the complex terrain and the meteorological phenomena that occur over it and that affect on air quality. Indeed in an alpine terrain, like the valdostan one, the meteorological variables present a great variability, that the models are not always able to reproduce with sufficient accuracy. Furthermore the situation results even more complicated by the fact that the region main valley is very deep and so difficult to be reproduced in detail. This master thesis is part of a collaboration with ARPA Valle D'Aosta and in particular is carried out the first part of the work. In this work the WRF meteorological model at resolutions of 1 km and 0.5 km with innovative configurations is used, in order to assess if the increase of resolution allows a more accurate reproduction of orography and of alpine meteorological phenomenology. The simulations results were qualitatively and quantitatively compared with the COSMO model ones at a 2.8 km resolution, used in a previous study of ARPA Valle D'Aosta, and with in-situ measured data near 24 stations uniformly distibuted over the entire region. The data analysis shown how, qualitatively, increasing the resolution, the model is able to reproduce the main meteorological phenomena that occur over a complex terrain. By a quantitative point of view the agreement with measured data depends on terrain morphology and on altitude and position of the station. The results of this first part of the work will then be used for the pollutant dispersion study, through FARM model, in order to evaluate the effect of a finer modelling on dispersive dynamics, for a more accurate identification of pollution sources and for study the influence of pollutant advection from bordering regions.