ACP Atmospheric Chemistry and Physics ACP 1680-7324 Copernicus GmbH Göttingen, Germany 10.5194/acp-12-3677-2012 Nudging technique for scale bridging in air quality/climate atmospheric composition modelling Maurizi A. 1 Russo F. 1 D'Isidoro M. 2 Tampieri F. 1 Istituto di Scienze dell'Atmosfera e del Clima, Consiglio Nazionale delle Ricerche, 40129 Bologna, Italy Italian National Agency for New Technologies, Energy and Sustainable Economic Development ENEA, Air Pollution Unit, via Martiri di Monte Sole, 4 40129 Bologna, Italy 24 04 2012 12 8 3677 3685 This is an open-access article ditributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited. This article is available from http://www.atmos-chem-phys.net/12/3677/2012/acp-12-3677-2012.html The full text article is available as a PDF file from http://www.atmos-chem-phys.net/12/3677/2012/acp-12-3677-2012.pdf

The interaction between air quality and climate involves dynamical scales that cover a very wide range. Bridging these scales in numerical simulations is fundamental in studies devoted to megacity/hot-spot impacts on larger scales. A technique based on nudging is proposed as a bridging method that can couple different models at different scales. <br></br> Here, nudging is used to force low resolution chemical composition models with a run of a high resolution model on a critical area. A one-year numerical experiment focused on the Po Valley hot spot is performed using the BOLCHEM model to asses the method. <br></br> The results show that the model response is stable to perturbation induced by the nudging and that, taking the high resolution run as a reference, performances of the nudged run increase with respect to the non-forced run. The effect outside the forcing area depends on transport and is significant in a relevant number of events although it becomes weak on seasonal or yearly basis.

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