UMBC lidars have been operating non-stop since yesterday in support of the Maryland Department of the Environment, as Ozone and PM2.5 concentrations reached Code Orange and Yellow (Unhealthy for Sensitive Groups and Moderate, respectively) AQI levels along the eastern coast of the United States. Clear skies, northwesterly transport, and warm air advection aloft associated with a high pressure system over the Mid-Atlantic United States are triggering this multi-day poor air quality event. Lidar observations (attenuated backscatter was plotted in a logarithmic scale to easily highlight today's observations) show the planetary boundary layer (PBL) extending up to 2 km, and above the PBL particle pollution extending up 6 km. According to NOAA HYSPLIT 48 hours back trajectories (Google Earth merged image- NOAA HYSPLIT and MODIS Terra AOD from June 18) of the air mass above the PBL indicate it was located over the Midwest US, where 2 days ago NOAA HMS reported the presence of smoke from the Colorado High Park and Little Sand Fires.
Today's MODIS Terra AOD retrieval reveals high readings along the eastern US due to associated with system discussed above. The high readings north of Tennessee, according to NOAA's Hazard Mapping System Fire and Smoke Product are due to smoke from the fires in North Carolina.