Automated model reduction for atmospheric chemical mechanisms

EPA Grant Number: R840013
Title: Automated model reduction for atmospheric chemical mechanisms
Investigators: McNeill, V. Faye , Fiore, Arlene M , Westervelt, Daniel , Henze, Daven
Institution: Columbia University in the City of New York
EPA Project Officer: Chung, Serena
Project Period: August 1, 2020 through July 31, 2023
Project Amount: $799,699
RFA: Chemical Mechanisms to Address New Challenges in Air Quality Modeling (2019) RFA Text |  Recipients Lists
Research Category: Air , Air Quality and Air Toxics

Objective:

We will develop the Columbia University Atmospheric Chemistry Model Reduction (AMORE) algorithm, an automated tool for flexibly generating accurate condensed chemical mechanisms for use in atmospheric chemistry and air quality models. We will apply AMORE to develop an updated condensed gas-phase isoprene oxidation mechanism, and implement it into GEOS-Chem and CMAQ in order to study the impact of using condensed mechanisms on simulations of ozone, PM and components, and the air toxic HCHO.

Approach:

 AMORE will be developed based on a novel graph-based analysis algorithm and simplified quasi-steady state analysis. Using isoprene oxidation as a test case, we will apply AMORE to generate reduced gas-phase mechanisms, broadly applicable atmospheric conditions encountered in the US, starting from a state-of-the art full-complexity model. Mechanisms generated by AMORE will be tested in a box model in order to determine how model performance, compared to the full mechanism and to laboratory data from the literature, varies with mechanism size. Metrics for evaluation will include predicted concentrations and lifetimes for O3, NOx, OH, SOA precursors, and HCHO. A reduced mechanism chosen for a balance of accuracy and model size will be incorporated into global GEOS-Chem and contiguous U.S.A. CMAQ. The updated models will be evaluated against observations from ground-based networks and recent field campaigns. Sensitivity simulations will be performed to evaluate the impact of the new condensed, updated mechanism on predictions of exceedances for ozone and PM, uncertainty in tracer concentrations, model simulation time, and contribution of anthropogenic versus biogenic emissions to air quality in both the condensed and default chemical mechanisms for comparison.

Expected Results:

Outputs will include the AMORE program, condensed mechanisms, updated versions of CMAQ and GEOS-Chem featuring the condensed mechanisms, and simulated tracer concentrations. AMORE will be open source and publicly available. By facilitating rapid, timely model updates it will enable the improved, sustained and consistent development of chemical mechanisms for air quality forecasting, research, and policy analysis.Our focus on air quality management metrics will help guide better air quality management strategies and improved risk assessment/ management.

Supplemental Keywords:

air, ambient air, toxics, particulates, ozone, modeling, general circulation models, chemical transport