Initial (IC) and boundary conditions (BC) are required in order to solve the set of stiff differential equations included in air quality models. In this work, the influences of ICeBC are analyzed in the northeastern Iberian Peninsula (NEIP) by applying MM5-EMICAT2000-CMAQ. A multiscale-nested configuration has been used to generate the ICeBC. The wider domain (D1) covers an area of 1392 X 1104 km2 centered in the Iberian Peninsula. Domain 2 (D2) covers an area of 272 X 272 km2 in the NEIP (D2) with high spatial and temporal resolution. The information related to BC has been supplied to D2 through one-way nesting. Different scenarios were considered (base case, increments of +50% in ozone (O3) IC, +50% in O3 BC, +50% in O3 precursors IC, +50% in O3 precursors BC and clean BC). The impacts of the IC on a site decrease with simulation time. Focusing on the conditions within the PBL, a 48-h spin-up time is sufficient to reduce the impact factor of IC to 10% or less for O3 since the influence of pervasive local emissions. The influences of BC are more important for areas near domain boundaries, especially in areas where the contribution of O3 precursors is due to a short-medium range transport.

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