AAAR 37th Annual Conference October 14 - October 18, 2019 Oregon Convention Center Portland, Oregon, USA
Abstract View
ISORROPIA-MCX: Implementation of the Multicomplex Variable Method into the Aerosol Thermodynamic Model, ISORROPIA
BRYAN BERMAN, Isaiah Sauvageau, Shannon Capps, Ryan Russell, Drexel University
Abstract Number: 691 Working Group: Aerosol Chemistry
Abstract Sensitivity analysis using atmospheric chemical transport models provides a deeper understanding of how specific emissions affect pollutant concentrations. Given a model with emissions as inputs and pollutant concentrations as outputs, this analysis is achieved by computing the partial derivatives of the underlying functions with respect to their input variables. Implementing higher-order sensitivity calculations can be quite difficult even though they are important to understanding nonlinear processes. A novel approach to sensitivity analysis leverages multicomplex variables to improve accuracy over the finite difference method and ease of implementation over the decoupled direct method (DDM).
Here, the multicomplex variable method (MCX) is implemented in the inorganic aerosol thermodynamic equilibrium model, ISORROPIA, which treats the Na+ - SO42- - HSO4- - NH4+ - NO3- - Cl- - H2O aerosol system (ISORROPIA-MCX). Specifically, the first- and second-order sensitivities of an inorganic species in the aerosol or gaseous phase with respect to the total concentrations are calculated. ISORROPIA-MCX is beneficial because there are enough inputs and outputs to demonstrate a main advantage of the method, which is simultaneously calculating multiple sensitivities. This is useful for understanding many atmospheric processes such as determining how much an aerosol constituent influences aerosol acidity. Furthermore, the ability to compute higher order derivatives is useful when the functions are nonlinear as it avoids subtractive cancellation and numerical round-off errors. Since thermodynamics is a nonlinear process and ISORROPIA uses nonlinear functions, we demonstrate the advantages of calculating higher order sensitivities using MCX. This work demonstrates the multi-complex variable method in ISORROPIA and shows its utility for investigating aerosol acidity