Development of Hybrid Eulerian and Lagrangian Modeling Approaches to Investigate High Ozone Events in the Houston Metropolitan Area

Texas Air Quality Study 2000 measurements revealed that ozone productivity in the Houston Ship Channel area was abnormally higher than other comparable cities in USA due to the large emissions of highly reactive unsaturated hydrocarbons (alkenes). However, Eulerian air quality models used for the development of Houston State Implementation Plan and related modeling research showed much lower ozone productivity even with substantially increased alkene emissions. On the other hand, several Lagrangian plume models successfully reproduced the observed high ozone productivity through the adjustment of the model inputs including emissions, background concentrations, and meteorological parameters. Because the Eulerian and Lagrangian modeling systems utilized vastly different inputs, it was difficult to compare the results directly. In this paper, we will investigate the efficacy of the Eulerian and Lagrangian modeling approaches in reproducing the measured ozone productivity in the Houston Ship Channel area with the common model inputs used by the Eulerian modeling infrastructure. Three state-of-science modeling tools underdevelopment are; (1) multi-resolution Eulerian modeling tool, CMAQ/SAFE; (2) a hybrid Lagrangian model, CMAQ/Trajectory-Grid; and (3) a hybrid Lagrangian column model, CMAQ/STOPS. We will identify whether the different estimations of ozone productivity among these systems are coming from either the grossly different model inputs or details of model configurations. The combination of these state-of-science modeling tools provides a unique opportunity to isolate the real-world physical processes from the constraints of certain modeling paradigms.