The EPA AirNow KML image (left) shows Moderate AQIs caused by heightened concentrations of PM2.5 in the East and in Southern California. The Southeastern US is experiencing elevated levels of ozone, reaching points of Unhealthy for Sensitive Groups (USG) mostly in Maryland and in central Georgia. These levels start to peak around 3:00 PM, as seen in the combined ozone and PM2.5 loop (right). As previously mentioned in past posts, the Moderate PM2.5 readings in Texas are presumably on account of Saharan Desert dust. As for the rest of the South, temperatures are climbing with a high pressure system bringing in a few showers, causing the stubborn build up of PM2.5. LA and Phoenix are also experiencing the same problems, two really hot and air polluted cities, which is understandable this time of year.
The NAAPS model (left) predicts dust and sulfates to be the culprits behind what we are seeing in the Southeast. The model also shows dust ranging from 0.1 to 0.4 blowing over the central US while sulfate surface concentrations reaching levels of 0.2 as well as high concentrations of Nitrates (KNMI OMI image, bottom) cover most of the Eastern US. HMS imagery (right) shows lack of any significant fires or smoke plumes over the country. However, light to medium smoke from the wildfires between Lake Athabasca and the Great Slave Lake in Canada are spreading over most of the Northwestern territories.