Impact of meteorology on air quality modeling over the Po valley in northern Italy

Abstract

A series of sensitivity tests has been made on both a meteorological model (MM5, Mesoscale Meteorological Model) and a chemical transport model (CHIMERE) to better understand the reasons for the underestimation of modeled particulate matter (PM) concentrations in the Po valley in winter. For the January 2005, time period chosen to perform the sensitivity tests, different techniques to nudge meteorological observations from regulatory networks into MM5 are explored to improve the model performance, especially the simulation of the frequent low wind regimes in this area. The sensitivity of the CHIMERE modeled PM concentrations to these different meteorological inputs are then evaluated. A further analysis of the CHIMERE model and in particular the in-cloud scavenging and vertical diffusion schemes reveals the need of improving some parameterizations when the model is applied in areas with frequent episodes of mist, fog and low stratus, as the Po valley in winter. Sensitivity of modeled PM to turbulence parameters, wind, temperature and cloud liquid water content both for surface and for vertical profiles in one of the most polluted and complex areas in Europe are discussed.JRC.H.2 - Air and Climat