U.S. Air Quality

“Unhealthy for sensitive groups” in Georgia this morning but mostly “Good” over the country.

According to today’s late afternoon AIRNow’s EPA PM2.5 map (top, left), the air quality is mostly “good” through out the country except for some relatively scarce “moderate” air quality conditions. On another hand, Georgia experienced “unhealthy for sensitive groups” conditions until the early afternoon (top, right). This is probably due to the remains of fire activity in the region as reported yesterday by the SSD fire team at NOAA.

Today’s MODIS TERRA AOD map (bottom, left) shows strong light extinction values over Iowa, Nebraska and Missouri as well as over the Atlantic, offshore from North and South Carolina. The HMS map shows no particular smoke plume over those areas. Also, a closer look at those two regions (MODIS TERRA RGB image over the Midwest and the Atlantic, bottom right), shows a significant cloud cover that prevents us from seeing any kind of particle event.

Let’s note that the strong MODIS AOD values could be due to cloud shadow contamination. According to a paper in 2005 about the residual cloud contamination on MODIS estimates of aerosol over ocean [Kaufmann et al., 2005], it has been found that despite the MODIS unique cirrus detection channel, and vigorous spatial-spectral cloud rejection, the total cloud contamination (due to thin cirrus and lower broken clouds) contributes to over-estimate the global aerosol average optical thickness by 0.02.