Long-Term Evaluation of the AIRPACT Air Quality Forecast Skill for the Pacific Northwest

Long-term evaluation of the AIRPACT air quality forecast skill for the Pacific Northwest.

Author’s: Jordan Munson, Joseph Vaughan, Brian Lamb, and Yunha Lee

The Air Indicator Report for Public Awareness and Community Tracking (AIRPACT) system forecasts daily air quality (AQ) over the Pacific Northwest (PNW) region, with the goal of providing air quality information to the public. Since 2001, the AIRPACT forecasting system has been successfully operated by Washington State University (WSU) for the NW-AIRQUEST’s air quality consortium. AIRPACT consists of the Sparse Matrix Operator Kernel Emissions (SMOKE) Model to provide temporal and spatial emissions, the Community Multiscale Air Quality Modeling (CMAQ) system to simulate hourly ozone and particulate matter and related precursor concentrations over PNW region, and meteorology forecasts based on Weather Research and Forecasting (WRF) model operated by the University of Washington. The AIRPACT forecast is publicly available through our website (http://lar.wsu.edu/airpact/), where current and past forecasts can be accessed. We have evaluated AIRPACT for the last ten years (2009 -2018) against the EPA Air Quality System (AQS) observations. During this period, AIRPACT has been intermittently updated with improved physical and chemical processes as well as with updated emissions and higher resolution modeling domains. Forecast output has been archived for AQS stations throughout the Northwest, although data availability for certain sites has been intermittent. Our evaluation results document how overall forecast skill has changed as the AIRPACT system has evolved. AIRPACT predicts significant trends reflected in observations, but generally over-predicts ozone and has a tendency to under-predict particulate matter. The AIRPACT system’s ability to predict these values has changed subtly over the version updates, but generally has improved over time.