The impact of MM5 and WRF meteorology over complex terrain on CHIMERE model calculations

• Main Authors: A. de Meij, A. Gzella, C. Cuvelier, P. Thunis, B. Bessagnet, J. F. Vinuesa, L. Menut, H. M. Kelder
• Format: Article
• Language: English
• Published: Copernicus Publications 2009-09-01
• Series: Atmospheric Chemistry and Physics
• Online Access: http://www.atmos-chem-phys.net/9/6611/2009/acp-9-6611-2009.pdf

The objective of this study is to evaluate the impact of meteorological input data on calculated gas and aerosol concentrations. We use two different meteorological models (MM5 and WRF) together with the chemistry transport model CHIMERE. We focus on the Po valley area (Italy) for January and June 2005. <br><br> Firstly we evaluate the meteorological parameters with observations. The analysis shows that the performance of both models in calculating surface parameters is similar, however differences are still observed. <br><br> Secondly, we analyze the impact of using MM5 and WRF on calculated PM₁₀ and O₃ concentrations. In general CHIMERE/MM5 and CHIMERE/WRF underestimate the PMv concentrations for January. The difference in PM₁₀ concentrations for January between CHIMERE/MM5 and CHIMERE/WRF is around a factor 1.6 (PM₁₀ higher for CHIMERE/MM5). This difference and the larger underestimation in PM₁₀ concentrations by CHIMERE/WRF are related to the differences in heat fluxes and the resulting PBL heights calculated by WRF. In general the PBL height by WRF meteorology is a factor 2.8 higher at noon in January than calculated by MM5. This study showed that the difference in microphysics scheme has an impact on the profile of cloud liquid water (CLW) calculated by the meteorological driver and therefore on the production of SO₄ aerosol. <br><br> A sensitivity analysis shows that changing the Noah Land Surface Model (LSM) in our WRF pre-processing for the 5-layer soil temperature model, calculated monthly mean PMv concentrations increase by 30%, due to the change in the heat fluxes and the resulting PBL heights. <br><br> For June, PM₁₀ calculated concentrations by CHIMERE/MM5 and CHIMERE/WRF are similar and agree with the observations. Calculated O₃ values for June are in general overestimated by a factor 1.3 by CHIMERE/MM5 and CHIMERE/WRF. High temporal correlations are found between modeled and observed O₃ concentrations.