Operational chemical weather forecasting with the ECCC online Regional Air Quality Deterministic Prediction System version 023 (RAQDPS023) – Part 1: system description

The online version of the Regional Air Quality Deterministic Prediction System (RAQDPS) is a chemical weather forecast system that has been employed operationally by Environment and Climate Change Canada (ECCC) since 2009. It is run twice per day to produce 72 h forecasts of hourly 10 km abundance fields of three key predictands, NO2, O3, and PM2.5 total mass, as well as other gas-phase chemical species, PM2.5 chemical components, and dry and wet deposition for Canada, the contiguous U.S., and northern Mexico. The forecasts of NO2, O3, and PM2.5 are needed to calculate the Air Quality Health Index (AQHI), which is used to communicate current and forecasted pollutant levels to the Canadian public. Version 023 of the RAQDPS (RAQDPS023) went into service at ECCC in December 2021 and was replaced by the RAQDPS025 in June 2024. This paper provides the first full description of any version of the online RAQDPS. After giving a brief history of the ECCC operational air quality forecasting program, the authors provide a comprehensive description of the RAQDPS023 forecast system as well as shorter descriptions of several upstream and downstream forecast and analysis systems. The latter include two upstream operational meteorological forecast systems that were based on version 5.1.0 of the ECCC Global Environmental Multiscale (GEM) numerical weather prediction model, one which used a global configuration, the Global Deterministic Prediction System (GDPS 8.0.0), and the other which used a regional configuration, the Regional Deterministic Prediction System (RDPS 8.0.0). An emissions processing system, an Updateable Model Output Statistics-based system for bias-corrected station-specific pollutant concentration forecasts (UMOS-AQ), and a regional objective analysis system for surface pollutant concentration fields, the Regional Deterministic Air Quality Analysis system (RDAQA 2.0.0), are also described.The online version of the Regional Air Quality Deterministic Prediction System (RAQDPS) is a chemical weather forecast system that has been employed operationally by Environment and Climate Change Canada (ECCC) since 2009. It is run twice per day to produce 72 h forecasts of hourly 10 km abundance fields of three key predictands, NO2, O3, and PM2.5 total mass, as well as other gas-phase chemical species, PM2.5 chemical components, and dry and wet deposition for Canada, the contiguous U.S., and northern Mexico. The forecasts of NO2, O3, and PM2.5 are needed to calculate the Air Quality Health Index (AQHI), which is used to communicate current and forecasted pollutant levels to the Canadian public. Version 023 of the RAQDPS (RAQDPS023) went into service at ECCC in December 2021 and was replaced by the RAQDPS025 in June 2024. 

This paper provides the first full description of any version of the online RAQDPS. After giving a brief history of the ECCC operational air quality forecasting program, the authors provide a comprehensive description of the RAQDPS023 forecast system as well as shorter descriptions of several upstream and downstream forecast and analysis systems. The latter include two upstream operational meteorological forecast systems that were based on version 5.1.0 of the ECCC Global Environmental Multiscale (GEM) numerical weather prediction model, one which used a global configuration, the Global Deterministic Prediction System (GDPS 8.0.0), and the other which used a regional configuration, the Regional Deterministic Prediction System (RDPS 8.0.0). An emissions processing system, an Updateable Model Output Statistics-based system for bias-corrected station-specific pollutant concentration forecasts (UMOS-AQ), and a regional objective analysis system for surface pollutant concentration fields, the Regional Deterministic Air Quality Analysis system (RDAQA 2.0.0), are also described.