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Abstract
Abstract. The global Flow-following finite-volume Icosahedral Model (FIM), which was developed in the Global Systems Laboratory (GSL) of NOAA, has been coupled inline with aerosol and gas-phase chemistry schemes of different complexity using the chemistry and aerosol packages from WRF-Chem v3.7, named FIM-Chem v1. The three chemistry schemes include (1) the simple aerosol modules from the Goddard Chemistry Aerosol Radiation and Transport model that includes only simplified sulfur chemistry, black carbon (BC), organic carbon (OC), and sectional dust and sea salt modules (GOCART); (2) the photochemical gas phase of the Regional Atmospheric Chemistry Mechanism (RACM) coupled to GOCART to determine the impact of more realistic gas-phase chemistry on the GOCART aerosol simulations (RACM_GOCART); and (3) a further sophistication within the aerosol modules by replacing GOCART with a modal aerosol scheme that includes secondary organic aerosols (SOAs) based on the volatility basis set (VBS) approach (RACM_SOA_VBS). FIM-Chem is able to simulate aerosol, gas-phase chemical species, and SOA at various spatial resolutions with different levels of complexity and quantify the impact of aerosol on numerical weather prediction (NWP). We compare the results of RACM_GOCART and GOCART schemes which use the default climatological model fields for OH, H2O2, and NO3. We find significant reductions of sulfate that are on the order of 40 % to 80 % over the eastern US and are up to 40 % near the Beijing region over China when using the RACM_GOCART scheme. We also evaluate the model performance by comparing it with the Atmospheric Tomography Mission (ATom-1) aircraft measurements in the summer of 2016. FIM-Chem shows good performance in capturing the aerosol and gas-phase tracers. The model-predicted vertical profiles of biomass burning plumes and dust plumes off western Africa are also reproduced reasonably well.
Highlights
The impacts of aerosol on weather and climate are generally attributed to the direct, semidirect, indirect, and surface albedo effects, with the direct effect predominating radiative forcing over a global scale (e.g., Bauer and Menon, 2012)
The detailed variations of the O3 and CO vertical profiles still show some slight differences between the model and observation, but the model generally forecasts the vertical changes with altitude, and the CO using RACM_GOCART is slightly lower than that of the RACM_SOA_VBS scheme above 5 km height
We investigate the relationships of some key species for the biomass burning plumes observed on 15 and 17 August 2016 between 22◦ S and 22◦ N below 6 km (Fig. 17) for the RACM_SOA_VBS scheme
Summary
The impacts of aerosol on weather and climate are generally attributed to the direct, semidirect, indirect, and surface albedo effects, with the direct effect predominating radiative forcing over a global scale (e.g., Bauer and Menon, 2012). Wang et al, 2014; Colarco et al, 2014) Since it is increasingly common for modeling systems to start using prognostic online aerosol schemes and more accurate emissions, many studies exist that show the importance of including aerosols at least for case studies or over limited time periods. The current real-time forecast uses simple bulk aerosol modules from the Goddard Chemistry Aerosol Radiation and Transport (GOCART) model, with a simplified chemistry for sulfate production. This chemistry scheme does not include NOx/volatile organic compound (VOC) gas chemistry or secondary organic aerosol (SOA) formation.
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