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Performance studies of planetary boundary layer schemes in WRF-Chem for the Andean region of Southern Ecuador

Abstract:

In tandem with emissions, the dynamics of the Planetary Boundary Layer (PBL) strongly define the concentration of pollutants in the atmosphere. The PBL parameterization schemes of numerical models need to be assessed to identify which one provides the best performance. We simulated the meteorology and transport of pollutants in Cuenca (Andean region of Southern Ecuador, 2400 masl) during September 2014, using the Carbon Bond Mechanism Z (CBMZ) for gaseous species and the Model for Simulation Aerosol Interactions and Chemistry (MOSAIC) for aerosol, from the Weather Research & Forecasting with Chemistry (WRF-Chem) model. Simulations were done under 6 PBL schemes: 1 Yonsei University, YSU; 2 Mellor-Yamada-Janjic, MYJ; 3 Hong and Pang, GFS; 4 Mellor-Yamada Nakanishi and Niino Level 2.5, MYNN2; 5 Mellor-Yamada Nakanishi and Niino Level 3, MYNN3; 6 Asymmetric Convective Model PBL, ACM2. The MYJ (local, 1.5 order of closure) and YSU (nonlocal, first order of closure) schemes showed on average the best skill, with capturing 81% and 78% of short-term air quality observations. For the MYJ scheme, the inclusion of direct effects between aerosol and meteorology increased the percentage of capturing of short and long-term air quality by 5% and 13% respectively, in comparison with modeling without feedbacks. In the future it is necessary to explore the effects in modeling of direct and indirect feedbacks, in combination with other parameterizations and aerosol-chemical mechanisms.