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AIr pollution forecasting

By: Dr. Jeff Masters, 2:49 PM GMT on May 18, 2006

Over the past decade, more state and local agencies have begun air quality forecasting for their communities. Today, about 300 cities nationwide are issuing air quality alerts based on forecast concentrations of known pollutants such as ozone and particle pollution, but have been doing so without the benefit of the kind of high-powered national forecasting technology and guidance that supports local weather forecasts. However, this is changing this year, with the arrival of new NOAA forecasting guidance to improve forecasters� ability to predict the onset, severity, and duration of poor air quality. For communities in most of the country, this will be the first time that comprehensive air quality predictions, with hour-by-hour information for cities, suburbs and rural communities alike will be available.

Figure 1. Ozone pollution forecast for 7pm EDT May 18, 2006, generated by NOAA's new air pollution forecasting system. With a major push of clean Canadian air over the eastern half of the country, the usual pattern of pollution over the Northeast and Midwest is absent today.

NOAA, in partnership with EPA, has implemented the first stages of an air quality forecast (AQF) capability. Now providing ozone forecast guidance for the eastern U.S. (predictions available at http://www.nws.noaa.gov/aq), the AQF capability uses the National Weather Service�s most advanced operational computer weather models at NOAA�s National Centers for Environmental Prediction (NCEP) coupled with a community multi-scale air quality (CMAQ) chemical transport model to produce daily forecast guidance for surface ozone. Meteorological information such as current and predicted temperature, humidity, winds, cloudiness, and precipitation, combined with pollutant emissions data supplied by EPA, are input to CMAQ to predict ozone concentrations through the next day. In summer, 2006 an experimental version of the AQF capability will cover the lower 48 states. Currently, the AQF capability covers the eastern US from the Atlantic Seaboard to the Mississippi Valley, with hourly and 8-hourly forecast ozone concentrations out to midnight, next day, at 12 km (about 7 miles) grid resolution. This information, converted to EPA�s health-based Air Quality Index (AQI) is also available on EPA�s AIRNow website.

In the next few years, the operational ozone prediction domain will be expanded still further to include Alaska and Hawaii and the forecast range will be extended out to several days. Also in development are predictions of airborne particulate matter (PM). As a component of the eventual PM forecast capability, a daily smoke forecast tool is being tested experimentally. For this tool, NOAA�s National Environmental Satellite and Data Information Service provides fire locations of active fires from complex satellite-based imaging techniques. Smoke transported from these fires is simulated with a computer transport model called HYSPLIT linked to NWS� operational weather forecast models. Predictions of the smoke are updated each morning and provided on a web site at http://www.nws.noaa.gov/aq-expr. State and local air quality forecasters will be able to use the expanding guidance when they prepare their forecasts or issue local alerts for their communities. The public, especially those with greater sensitivity to poor air quality, will be able to see hour-by-hour trends for the entire Nation and take appropriate actions.

I'll conclude my series on air pollution tomorrow, with a look at why one of NOAA's P-3 weather research aircraft will be flying an air pollution research project this summer in Texas instead of chasing hurricanes.

Jeff Masters

Air and Water Pollution

The views of the author are his/her own and do not necessarily represent the position of The Weather Company or its parent, IBM.