March 17, 2009
Smoke and Haze in the Midwest Ahead of an Advancing Cold Front; Code Yellow/Orange PM2.5 Air Quality in Southern California
There are two major areas of elevated PM2.5 concentrations in the nation today, as indicated by the loop of PM2.5 AQI values (below on left). The Los Angeles and San Diego, California metropolitan areas are observing scattered readings of Code Yellow (Moderate), with Code Orange (Unhealthy for Sensitive Groups) in Riverside County, most likely due to haze. A more extensive area of Code Yellow air quality is spread across the Ohio River Valley, much of the Great Lakes, and portions of the Central Plains, with a few isolated Code Orange readings. The polluted air mass is evident in today’s MODIS Terra true color image (below on right overlaid with AQI values).
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Satellite and meteorological evidence suggests that a combination of smoke from agricultural fires and haze in a stagnant air mass ahead of an advancing cold front is responsible for the Midwestern air quality situation. Today’s MODIS Terra AOD image for EPA Region 5 (below on left) indicates elevated AOD in southern Michigan. In addition, NOAA’s Hazard Mapping System (HMS) Fire and Smoke Product (below on right) identified a large smoke plume in the same region, which HMS attributed to agricultural burns that occurred yesterday in Arkansas, Oklahoma and Kansas.
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As Ray noted on Sunday, ozone generation is ramping up again in some parts of the country. The Texas Commission on Environmental Quality issued an Ozone Watch for the Houston, Galveston, and Brazoria areas today because atmospheric conditions are favorable for generation of high levels of ozone. Currently, at 5:30 PM EDT, ozone air quality is in the Code Green (Good) range in the Houston-Galveston-Brazoria area, but the NOAA-EPA National Air Quality Forecasting System numerical ozone model (below) indicates that Texas, the Southwest, and southern Plains could see 8-hour ozone levels in the upper end of the Code Yellow range today.
