Computationally efficient modeling of atmospheric chemistry via Fully Equivalent Operational Models (FEOMs)
S.W. Wang, P.G. Georgopoulos (EOHSI, UMDNJ - R.W. Johnson Medical School
and Rutgers University);
G. Li, H. Rabitz (Department of Chemistry, Princeton University)
Atmospheric chemistry mechanisms are one of the most computationally intensive components of photochemical air quality simulation models (PAQSMs). Chemical kinetics calculations can consume as much as 90% of the total CPU time in simulations that employ chemistry-transport modules with comprehensive photochemical models. To relieve this computational burden, this work introduces a high-speed fully equivalent operational model (FEOM) to perform the chemical kinetics calculations. A high-speed FEOM for these types of calculations is based on expressing the concentrations of the chemical species as hierarchical correlated function expansions which capture the kinetic input-output relationships. The FEOM can be used to directly calculate output species concentrations and related chemical properties at a given reaction time based on the initial input species concentrations. The test application of the FEOM method on atmospheric chemistry presented here focuses on a photochemical box model study that utilizes the Carbon Bond Mechanism - IV (CB4). This study shows that the FEOM calculations of chemical species concentrations can maintain accuracy comparable to conventional chemistry solvers (e.g., the Gear-type implicit solvers), while being orders of magnitude faster.