WRF-CALGRID: Un sistema di previsioni giornaliere dell'inquinamento da ozono in Toscana

At the LaMMA laboratory the WRF-CALGRID ozone-pollution regional forecasting system has been developed, which is based on the CALGRID photochemical grid dispersion model, developed by Earth Tech Inc. and distributed by the California Air Resource Board. The system, focused on the Tuscany region, is based on two daily forecasts, one reproducing the meteorology over the study domain, and the other providing chemical boundary conditions. Meteo forecasts are performed by the WRF regional scale model, which is operative at LaMMA for the daily forecasting service, whereas boundary conditions are forecast by the CHIMERE regional chemical and transport model of the PREV'AIR European-scale air quality forecasting system. Thus, the run of the WRF-CALGRID system starts only once both meteorological and chemical forecasts are available. Each day a 96 hours simulation is run starting from 00:00 A.M. of the preceding day, which is merely used to inizialize the system. The result is then a 3-days forecasting: today, tomorrow, and the day after tomorrow. Daily meteo forecasts over the domain, performed by the WRF model at a 10 Km resolution, are scaled to the 4 Km system's final resolution through the CALMET meteo postprocessor. Chemical forecasts needed to set boundary conditions to CALGRID are provided by the CHIMERE model. Since CHIMERE uses the MELCHIOR chemical mechanism (44 species and 120 reactions) being different from the CALGRID's one, a suitable species conversion proved to be necessary to the SAPRC-90 mechanism (50 species and 129 reactions) implemented in CALGRID. Emission data over the study domain are provided by the IRSE regional emission inventory of the Tuscany region Authority. WRF-CALGRID system results are ozone daily mean and maximum concentrations over the Tuscany region. The system has been preliminary applied during the month of May 2007. Results achieved over this experimental time period showed a good accuracy level with respect to observations provided by chemical stations against local comparison has been made to. Starting from June 1st 2007, the WRF-CALGRID forecasting system is operative at LaMMA and may be accessed at the address: http://www.lamma.rete.toscana.it/ eng/aria/index_concO3_d0.html.