Evaluation of 3-day forecasts of Ozone and PM2.5 from the Air Indicator Report for Public Awareness and Community Tracking (AIRPACT) model

The AIRPACT (Air Indicator Report for Public Awareness and Community Tracking) model, version 5, is an air quality forecasting system that predicts air pollutants concentrations and depositions. The simulation domain is the Pacific northwestern United States, including Washington, Oregon, and Idaho. It was developed at Washington State University in 2001 and has been operating for over 20 years. In this research we extended the forecast period from 48 hours to 72 hours (3 days) and provided evaluation of Ozone and PM2.5 forecasts. The model performance is evaluated relative to ground-based measurements at AirNow observational sites; 27 for Ozone and 150 for PM2.5 and categorized to Urban, Suburban, and Rural stations. The evaluation of PM2.5 shows good agreement with observations during wildfire season and during periods of winter stagnation, while the evaluation for ozone shows a significant bias in the model during nighttime.