A contribution to subproject SATURN

Giovanna Finzi*, Giuseppe Brusasca, Patrizia Buttini, Giuseppe Calori, Giorgio Catenacci, Cristina Cavicchioli, Franco Desiato, Francesca Lena, Arnaldo Longhetto, Alberto Marzorati, Umberto Pellegrini, Guido Pirovano, Maurizio Riv a, Camillo Silibello and Marialuisa Volta

A prototype of integrated modelling system has been designed for Lombardia region, a densely inhabited and industrialized area, located in the Po Valley (Northern Italy), where frequent ozone episodes occur mainly during summer mont hs. The system includes 3D meteorological preprocessors, a flexible emission inventory module (POEM) and two photochemical transport models (CALGRID and STEM II). An experimental activity has also been performed in Milan urban area in connection to PIPAPO /LOOP campaign in spring 98.

The final goal of the project is to set up a decision support system allowing the urban and regional environmental managers to examine alternative emission scenarios, in order to delineate proper photochemical pollutants abatement s trategies. Starting from the implementation and validation on Milan metropolitan area, the objective is to assign the general methodological and input/output requirements of the system, in view of its possible application to other urban areas in collabora tion with local and national environmental agencies (see Fig. 1).

The activities performed by the research operational units are the following:

• selection of an intense ozone episode revealed during June 1996 and preparation of land-use, meteorological and chemical input data for model runs on a 240x232 km² domain covering all Lombardia Region;
• executions of preliminary simulations and first evaluation of the modelling system versus experimental data coming from local monitoring network;
• critical review of methods for the estimate of mixing height, turbulence parametrization and vertical diffusivities in urban areas;
• development of an emission model to perform spatial and temporal disaggregation and NMVOC splitting needed to provide the requested emission data for photochemical models;
• set-up of emission inventory data for episodic model runs on the simulation domain;
• execution of a preliminary experimental campaign in the Milan area in spring 1998 during the PIPAPO/LOOP campaign; ground level and vertical profile measurements of meteorological and chemical variables (examples are shown in Fig. 2).

A preprocessor model for emission input data (POEM, i.e. POllutant Emission Model) has been designed and applied to Lombardia Region. The model can provide both emission inventory and alternative scenario estimations by means of a m ixed approach. Starting from the annual national inventory, the top-down procedure resolves the aggregated emission data in spatial and time scale, splitting NMVOC into more defined species, while the bottom-up algorithm estimates emission f ields, taking into account local data or possible alternative pollution reduction strategies concerning particular source sets (traffic, heating, …). The disaggregation procedure is developed on three steps: spatial disaggregation, time modulation and spl itting of total NMVOC emission into components; different paths are allowed to the user in order to get emission output data according to the environmental impact simulation purposes. As emissions of each category can, in general, be attributed to one or more technologies, fuels and activities, the procedure steps are not independent, but connected each other beyond the particular pollution process having its own spatial distribution, temporal modulation and VOC speciation profile. Therefore the POEM mode l is designed to be technology-fuel oriented. The model outputs are all possible combinations of the following tasks:

• spatial disaggregation: starting from territorial level NUTS3 emissions, corresponding to the province level, the model estimates municipality emissions; then it is possible to distribute emissions on a gridded domain (Fig. 3 shows an output example, the NOx annual gridded anthropogenic emission field on Lombardia region);
• time modulation: starting from annual data base, the model can provide emission fields for an assigned time interval on a daily or hourly base;
• VOC splitting: the total VOC amount is splitted into SAROAD classification of compounds and lumped into emission classes, as needed by the photochemical transport model.

Taking into account recent EU guidelines on traffic emission scenarios scheduled for 2005, the corresponding emission fields have been estimated for the studied area and preliminary simulations of the consequent urban air quality impact have been performed; results point out the inadequacy of the assumed pollution abatement strategies and the need of a deeper understanding of the phenomenon, both from the available data and the scientific knowledge points of view.

Starting from the high interest related to Northern Italy area as for photochemical pollution phenomenon, due to geographical, meteorological and emission systems complexity, a strong need for co-ordination among the research and lo cal agencies teams working on the problem was evidenced; as a consequence, a proposal of assuming Lombardia region as a comparison and validation case study area for emission inventories, simulation models and urban experimental campaigns design was accep ted in the frame of EUROTRAC-2 Projects and a “Milan focal point” task force was established since summer 98.

• Insertion of analysed turbulence parametrizations in the whole modelling system and test against experimental data;
• ending of modelling activities on June’ 96 episode;
• preliminary modelling analysis of experimental data collected during spring 1998 Milano campaign;
• updating of the emission inventory to 1996 and future emission abatement scenarios processing;
• experimental campaign in Milan and Brescia in January-February 1999; VOCs sampling and analysis with diffusive sampler; data processing and analysis;
• future sustainable emission abatement scenarios processing.

This research was supported by MURST, Provincia di Brescia, ANPA (Italian National Environmental Agency), ENEL-SRI and Agip Petroli-ENI.