MyCMAQ: Operational Air Quality Forecast System for Malaysia and Southeast Asia

MyCMAQ is a real-time operational air quality forecasting system developed to provide routine, high-resolution forecasts of atmospheric pollutants over Malaysia and the Southeast Asia region. The system comprises two major modelling components: the Weather Research and Forecasting model with the Advanced Research WRF dynamical core (WRF-ARW) and the Community Multiscale Air Quality (CMAQ) model. MyCMAQ is maintained and supported by the Malaysian Meteorological Department (MetMalaysia) as part of its commitment to environmental monitoring and open data dissemination.

Meteorological fields for MyCMAQ are generated using WRF-ARW version 4.5.2. Initial and lateral boundary conditions are provided by operational forecasts from the Global Forecast System (GFS), updated at six-hour intervals. The modelling framework employs a two-domain nested configuration, consisting of a regional domain at 27 km horizontal resolution covering Southeast Asia and a higher-resolution domain at 9 km focusing on Malaysia and its surrounding areas. Physical parameterisation schemes are selected to represent tropical atmospheric processes, including convection, boundary layer dynamics, land–surface interactions, and large-scale monsoon circulation patterns.

Air quality simulations are performed using the Community Multiscale Air Quality model version 5.5, developed by the US Environmental Protection Agency. The chemical configuration adopts the CB6r3 gas-phase mechanism coupled with the AE7 aerosol module, enabling the simulation of photochemical ozone formation, secondary aerosol production, and the transport and transformation of gaseous and particulate pollutants. CMAQ is driven by hourly meteorological outputs from WRF to ensure consistency between atmospheric dynamics and chemical processes.

Anthropogenic emissions in MyCMAQ are derived from the MIX-Asia emission inventory, which provides sector-resolved emissions for Asian countries, including industry, power generation, transportation, and residential activities. The MIX-Asia dataset is dynamically processed and spatially and temporally allocated to the model grids to ensure compatibility with the CMAQ framework and regional simulation requirements. Biomass burning emissions are obtained from the Fire INventory from NCAR (FINN) version 2.5.1 near-real-time product, which supplies daily global fire emission estimates. These emissions are processed into gridded, hourly, three-dimensional fields for use in CMAQ, allowing the system to capture rapid changes associated with wildfire and open burning events.

MyCMAQ forecasts are initialised daily at 00 UTC and extend up to five days ahead. Model outputs are produced at hourly resolution for both model domains. Forecast products include concentrations of particulate matter with aerodynamic diameters below 2.5 µm and 10 µm (PM₂.₅ and PM₁₀), ozone (O₃), nitrogen dioxide (NO₂), sulfur dioxide (SO₂), and black carbon. All MyCMAQ forecast products are made freely available to the public to support air quality awareness, scientific research, and environmental decision-making across Malaysia and Southeast Asia.