ACPD Atmospheric Chemistry and Physics Discussions ACPD 1680-7375 Copernicus GmbH Göttingen, Germany 10.5194/acpd-11-17177-2011 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 20 06 2011 11 6 17177 17199 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-discuss.net/11/17177/2011/acpd-11-17177-2011.html The full text article is available as a PDF file from http://www.atmos-chem-phys-discuss.net/11/17177/2011/acpd-11-17177-2011.pdf

The interaction between air quality and climate involves dynamical scales that cover an immensely wide range. Bridging these scales in numerical simulations is fundamental in studies devoted to megacity/hot-spot impacts on climate. The nudging technique 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 using a high resolution run on critical areas. 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, if a high resolution run is taken as a reference, there is an increase in model skills of low resolution run when the technique is applied. This improvement depends on the species and the season. The effect spreads outside the forcing area and remains noticeable over an extension about 9 times larger.

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