Ground-Level Ozone and Fine Particulate Matter Forecasting Research Products

Nationwide air quality forecast maps indicate areas of concern for poor air quality.

While outdoor air quality has improved dramatically over the past few decades, air pollution is still recognized as a major cause of acute and chronic respiratory and cardiovascular problems and annually leads to tens of thousands of premature deaths. The costs of health effects in the United States each year is more than $100 billion. Accurate air quality forecasts enable communities to take actions that can reduce the severity of episodes of poor air quality (e.g., encourage people to telecommute or take mass transit instead of driving). They also enable individuals to take protective actions that limit their own exposure to poor air quality, such as limiting exercise or staying indoors.

The Air Resources Laboratory’s  Air Quality Forecasting research helps to ensure that forecast models, run operationally by NOAA’s National Weather Service (NWS), provide consistently high quality forecast products and support air quality planners and managers, air quality forecasters, and the research community. To this end, ARL has led the research, configuration and testing of the National Air Quality Forecasting Capability, an integrated modeling system linking the National Weather Service’s numerical weather prediction model to the NOAA-EPA developed Community Multiscale Air Quality model. As a result of ARL’s research, NOAA has consistently improved operational air quality forecasting products.

The two most important air pollutants of concern are ground-level ozone (O3) and fine particulate matter (PM2.5). These pollutants are linked to serious health impacts, including chronic bronchitis, asthma, and premature deaths. They also contribute to reduced visibility (PM2.5), crop damage (O3), and greater vulnerability to disease in some tree species (O3).

Ozone, O3, is a gas typically produced from other air pollutants reacting in the presence of sunlight. O3 is a major constituent of smog. Motor vehicles, power plants, industrial operations, gasoline vapors, and chemical solvents, as well as natural processes, are emission sources of the pollutants that act to form ground-level O3. Fine particulate matter (PM2.5) is composed of tiny particles with a diameter of 2.5 micrometers or less (or less than 1/30th the width of a human hair). PM2.5 is especially dangerous to human health because fine particles can be inhaled into and accumulate in the respiratory system. PM2.5 is emitted directly into the air from combustion processes (burning of fossil fuels, residential fireplaces, agricultural burning, and fires), volcanic emissions, and windblown dust and can also form in the air as a result of chemical reactions.

ARL has a world class emission modeling team working with scientists in other NOAA laboratories, other federal agencies, and universities to improve air quality forecasting models and to generate data needed to model the significant processes that control the concentrations of ground-level O3.

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Air Quality Forecasting Research Products

An example map of ground-level ozone concentrations predicted for the continental U.S. The NWS generates such maps twice daily using an ARL- developed modeling system.

Pollutants released into the air can impact air quality, as well as terrestrial and aquatic ecosystems when the pollutants deposit to Earth. Effective targeting of air pollution controls depends on having good scientific understanding of which specific pollutant sources and regions are contributing to air and water quality issues. While much progress has been made in reducing releases of harmful air pollutants, many locations in the U.S. continue to experience problems associated with poor air quality. Air pollutants also damage crops and forests, degrade aquatic ecosystems, and contribute to climate change.

ARL evaluates and improves computer models used by NOAA’s National Weather Service to forecast the occurrence of ground-level ozone and fine particulate matter. These forecasts improve the ability of communities and individuals to respond to anticipated episodes of poor air quality by reducing pollutant emissions (e.g., limiting driving) and by taking personal protective measures (e.g., limiting outdoor exercise).

ARL also conducts research on the exchange of pollutants between the air and the Earth’s surface. This improves scientific understanding of atmospheric chemistry and guides policies concerning air quality management and ecosystem health. ARL researchers focus on pollutants, such as mercury, reactive nitrogen, and sulfur compounds, which can have significant impact on the environment and—in the case of mercury—human health.

ARL’s activities include: a) developing and applying a specialized modeling system that tracks mercury emissions and links these emissions to atmospheric transport, transformation, and deposition; b) conducting long- term, intensive ambient air monitoring of mercury; c) conducting short- term, process-level field studies for mercury and reactive nitrogen compounds; and d) supporting long-term, research-grade monitoring of pollutants in precipitation.

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