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Cloud processing of gases and aerosols in the Community Multiscale Air Quality (CMAQ) model: Impacts of extended chemistry
Citation:
Fahey, K., N. Sareen, A. Carlton, Bill Hutzell, AND D. Luecken. Cloud processing of gases and aerosols in the Community Multiscale Air Quality (CMAQ) model: Impacts of extended chemistry. 2017 International Aerosol Modeling Algorithms Conferences, Davis, CA, December 06 - 07, 2017.
Impact/Purpose:
This presentation describes the utilization of a new framework to study cloud chemistry in CMAQ. Here we summarize past work and look at the impacts of an expanded cloud chemistry mechanism on mode pollutant concentrations. Additional in-cloud SOA chemistry can lead to significant increases in predicted cloud SOA levels in the summer, both at the surface and aloft. Additional inorganic chemistry can impact sulfate and nitrate concentrations in the winter. This work is expected to contribute to more accurate modeling of the spatiotemporal evolution of pollutants in CMAQ and the NGAQM.
Description:
Clouds and fogs can significantly impact the concentration and distribution of atmospheric gases and aerosols through chemistry, scavenging, and transport. This presentation summarizes the representation of cloud processes in the Community Multiscale Air Quality (CMAQ) modeling system and their relative impacts on simulated gas and particulate concentrations, with a focus on the extendable aqueous-phase chemistry option (AQCHEM-KMT), available starting with CMAQv5.1. For AQCHEM-KMT, the Kinetic PreProcessor (KPP) was used to generate a Rosenbrock solver to integrate the stiff system of ordinary differential equations that describe the mass transfer, chemical kinetics, and scavenging processes of CMAQ clouds. The development of AQCHEM-KMT and the use of KPP facilitates straightforward implementation and investigation of more extensive cloud chemical mechanisms in CMAQ, as well as furthers our ability to investigate the impacts of microphysical parameters on cloud chemistry. With month-long summer and winter CMAQ simulations, we will examine the relative impacts of cloud chemistry and wet deposition on simulated gas and aerosol concentrations, paying special attention to the sensitivity of model response to choice of aqueous chemical mechanism as well as mass transfer and scavenging assumptions. Additionally we will investigate the relative importance of resolved vs. subgrid clouds on CMAQ cloud chemistry.
