Application of the Hyperdual-step Method in the Community Multiscale Air Quality Model (CMAQ) for the Assessment of Aerosol Formation from Volatile Chemical Products (VCPs)

JIACHEN LIU, Shannon Capps, Drexel University

     Abstract Number: 237
     Working Group: Chemicals of Emerging Concern in Aerosol: Sources, Transformations, and Impacts

Abstract
The Community Multiscale Air Quality (CMAQ) model is a chemical transport model utilized to study the physicochemical processes in the atmosphere using meteorology and emissions as inputs. CMAQ has helped researchers and policymakers to comprehend the complexities associated with aerosol formation processes. In policy-related scenarios, the first- and second-order partial derivatives of output variables, such as criteria pollutant concentrations, with respect to input variables, such as emissions, are often of interest to ascertain expected changes due to emissions control strategies. Several methods have been employed to address this challenge, such as the higher-order direct decoupled method (CMAQ-HDDM) and the adjoint method (CMAQ-adjoint). We recently developed a novel, augmented version of CMAQ (CMAQ-hyd) capable of computing numerically exact first- and second-order sensitivities of all modeled species concentrations with respect to select emissions. The EPA developed new emissions profiles to account for emissions from VCPs (Seltzer et al., 2021). We exploit the new emissions profiles and employ CMAQ-hyd to calculate sensitivities and evaluate the health impacts of VCP-related aerosol formation across the continental United States. This study demonstrates the novel application of the hyperdual-step method in CMAQ to enhance our understanding of aerosol formation from VCPs and the potential of the novel model being applied to answer other critical policy-related questions.