Since Monday we have conducted lidar observations at UMBC in support of Maryland Department of the Environment Air Quality Program. Our observations indicate the presence of particles aloft at heights between 2-6 km. Clouds were present throughout the first two days of observations. The clouds are represented in the figure by the intense red returns in our timeseries. HYSPLIT back-trajectories of the air mass between 2.5-4 km indicate that it originated in central Canada. The top right image is the HYSPLIT trajectories overlaid with last Monday's Aqua MODIS AOD retrieval indicating the presence of smoke particles over Baltimore.

NOAA HMS reported that remnant smoke originating from the wildfires in northwestern Canada is sweeping east and south into the northern central US moving east over the Great Lakes and extending to the Atlantic Seaboard and up through New England and into southern Quebec and New Brunswick. This smoke is the cause of the high AOD values reported in today's Aqua MODIS AOD retrieval. High AOD's were also reported over the Pacific Northwest, Montana and California.

Air Quality across the country seems better than it has been in days, with the areas of Moderate AQI seen in the EPA AQI loop below left largely near the coasts, except for some small spots popping up around the Great Lakes and Plains. Small areas of Unhealthy for Sensitive Groups and Unhealthy show up in central California, growing and shrinking by turns as the day goes on. The GASP AOD animation, below right, shows elevated AOD around central California and southern Texas. Also visible is a strip of elevated AOD stretching south from Canada and around the Great Lakes toward the Mid-Atlantic. The NWS wind imagery, below left, shows a counterclockwise circulation northeast of the Great Lakes, which would explain the drifting seen in the GASP animation and the curl in the smoke seen in the HMS image below right. This smoke is part of a plume covering much of Canada, largely originating in fires in the Northwest Territories and British Columbia. There is also a small area of smoke in central California that might be responsible for the higher AQIs in that area, as well as several fires in the Mississippi Valley and Southeast that might explain Moderate AQIs in this region.

The MODIS Terra image below (top left) shows areas of elevated AOD over the Great Lakes Region and Northern Canada, presumably from the light to heavy smoke originating from the NW Territories wildfire complex (HMS Google Earth image, top right). Remnant smoke from these wildfires last week loomed over most of the US. Today, the smoke surface concentration seems to have decreased except over the Great Lakes region and some areas in the central US. The low pressure system observed in today's NOAA Weather Map (bottom left) is most likely causing the aerosol mixing in the atmosphere, leading to healthier AQIs over much of the Eastern and central US.

Today's EPA AirNow forecast shows a spot of Unhealthy AQIs over central California, which eventually leveled to Moderate around 10:00 EDT. Another spot of Unhealthy AQIs popped up in central Washington around 12:00 EDT. The AQI for PM2.5 reached 170 in Leavenworth, Washington at this time, predicted to have been 64 - 128 ug/m^3 of smoke by the NAAPS Aerosol Model above (bottom right). USG conditions resurfaced in the same spot where the Unhealthy AQIs were noted in central California around 12:00 EDT. The HMS image above shows fires in this area with barely any visible smoke originating from them. The two new wildfires (both developed over the weekend) are the Sand Fire and El Portal and Dark Hole Fires, both reportedly still burning. In other news, a large dust cloud (presumably Saharan dust) is predicted by the NAAPS model to be traveling up the Caribbean, covering much of the Caribbean Islands and Central America. The MODIS Terra image above picks up high AOD levels over this area, just below Florida. Dust also seems to be a problem in the central US, predicted to reach 2.58 - 5.12 mg/m^3 over central Colorado.

The US and Canada continue to be covered by smoke. The HMS map shows most of North American impacted by the plumes from the West and the Northwest Territories. In Utah today, code Red or unhealthy conditions were seen overnight (below right).

In the east high AOD's were seen off Nova Scotia from transported smoke. The number of currently active fires in the Pacific Northwest is impressive. 36 fires are named on the National Forest Service fire page.

In Canada, the CALIPSO overpass on July 25 shows high and dense fire plumes.

Looking at the NOAA HMS Smoke and Fire Product (top left), the clumps of small red dots indicate masses of currently burning fires, with smoke plumes being indicated by the grey patches. The Great Slave and Bear Lake fires have created a large plume spanning into the Mid-Atlantic, with the heaviest smoke being in the Northeast portions of both Canada and the United States. The MODIS Aqua image (top right) illustrates clearly elevated AODs in the path of this plume, with the highest AODs corresponding to the high density areas of smoke. The HMS also picked up multiple plumes over the Central US stemming from the Nevada and Utah wildfires as mentioned yesterday by Daniel.

The EPA AIRNow combined AQI loop (bottom left) shows elevated AQIs in Utah and the Northeast, which could be a result of the smoke plumes. For the moderate AQIs in the Southeast, the main component was PM2.5, and the NAAPS Sulfate Model (bottom right) predicted elevated sulfate levels at 1800 UTC, which could explain the increased PM2.5 concentrations.

The EPA AQI loop, below left, shows areas of Moderate AQI across the Mid-Atlantic, Southeast, Great Plains, Rocky Mountains, and Pacific Southwest, with spots of Unhealthy for Sensitive Groups in the southern Plains, the Rocky Mountains, and Pacific Southwest. The HMS imagery, below right, shows smoke over the Rocky Mountains and Plains States from fires in Nevada and the Utah border, as well as a large swath from both these fires and those in the Northwest Territories stretching from the southern Plains through the Great Lakes region on into Canada. MODIS Aqua caught the smoke coming from the Bear Trap and Hampton fires in Nevada, in addition to a few clouds and their shadows, seen in the Google Earth image below.

The NWS air quality guidance below indicates that a combination of dust and ozone might be responsible for the elevated AQIs in southern California.

An enormous amount of smoke persists over much of Canada from large wildfire complexes throughout the Northwest Territories surrounding Great Slave and Great Bear Lake. The heavy smoke is visible in the MODIS Aqua rgb image below and is captured in today's AOD retrieval as well.

Nearly all of the US remains affected by remnant smoke from fires in Northwestern US and Canada, with some contribution from fires over East central Nevada. Clear zones include, Alaska, Washington, Oregon, California, Idaho, Nevada, Arizona, the Southeast US from the Mississippi River through North Carolina including all but the Florida panhandle. In today's MODIS Aqua AOD retrieval a large area of hazy aerosols and smoke can be seen across Oklahoma, Arkansas, Missouri, Kansas and Texas. US AQI levels were Moderate for PM2.5 along states on the eastern and southern edge of the smoke cloud, discussed above.