The center of tropical storm Hanna is off the Georgia coast right now (right: NWS Hurricane Center track forecast; left: UW MODIS Today rgb from MODIS Aqua and EPA AIRNow PM2.5), see right image with forecasted track as of 5 PM EDT. As you can see (compare to Amy's post on Tuesday), the storm track has shifted east. Hana will reach southern VA around 2 pm tomorrow and the D.C area later in the afternoon and it is expected that it will bring good air quality to the east. The storm has already brought good air quality to the southeast, but air quality is still primarily in the moderate range over the northeast (bottom: UW MODIS Today rgb from MODIS Terra and EPA AIRNow PM2.5). Ozone was the lead pollutant in some parts of New York, leading to code orange conditions in Albany.

ELF operated for approximately 36 hours to monitor the atmospheric boundary layer during today and yesterday's Air Quality Action Event. The PM2.5 ground monitors in the Washington DC-Baltimore metro area (left panel) show that during the time that ELF operated the PM2.5 AQI levels were Moderate-Unhealthy for Sensitive groups. From the lidar timeseries we can see how the boundary layer rose on September 3rd up to 1.75 km. During the night of the 3rd the winds shifted from a northern to a southerly flow (right panel) recirculating pollutants and bringing moisture/water vapor into the Mid-Atlantic region. This humidity rose the PM2.5 concentrations and extended the boundary layer close to 3 km. Water vapor mixing ratio timeseries from ALEX,the Raman lidar, confirm the presence of H2O vapor up to 3km (plot not shown).

The increase in the PM2.5 concentrations is associated to the increase of photons scattered back to the lidar receiver (figure below). Also, related to the change of direction and speed of last night winds was the formation of a low level jet, as shown in the wind profiler timeseries. This event was weaker that the one we experienced on June 13th. We observed a region of convergence, around 6:00 UTC, characterized by low wind speeds (~ 5 m/s) associated with a southerly wind shift, that results in aerosol lifting. After 6:00 UTC, a thick residual layer above the core of the low level jet is coincidental with directional shear.

Today’s MODIS TERRA RGB image (top, left) shows strong lingering haze over the upper east coast and the Atlantic, offshore from North Carolina all the way to Maine. This leads to strong MODIS TERRA AOD values (top, right), especially over Maryland, Delaware, New Jersey and Pennsylvania (above 0.6 at 550 nm). This haze appears to be partly composed of fine particles and contained in a (well mixed?) atmospheric boundary layer as “unhealthy for sensitive groups” levels are measured today at the ground in the states previously mentioned (EPA AIRNow’s PM2.5 map, bellow, left). The same “Unhealthy for sensitive groups” levels are recorded on today’s EPA AIRNOw’s ozone level map (bellow, right).
Stay tuned to read what our ground-based LIDAR profile analyst, Ruben Delgado, has to say about the vertical distribution of aerosols over Baltimore, Maryland…

Poor air quality over the East coast will not last as the intense heat breaks down tomorrow, due to the landfall of tropical storm Hanna (clearly visible on today’s MODIS TERRA RGB image). According to forecasters at the National Hurricane Center, it is increasingly unlikely that Tropical Storm Hanna will strengthen to hurricane status before making landfall tomorrow.

Finally, the rest of the country shows mainly “good” air conditions, to the exception of California where PM2.5 levels are “moderate” and Ozone levels are “unhealthy for sensitive groups”.

Today’s Terra MODIS image (below left) is a dramatic depiction of both Tropical Depression Gustav, nearly stationary over the mid-Mississippi River Valley, and lingering haze in the Midwest. Haze can be seen to the south and southwest of Lake Erie (right side of left picture). Zooming out to a more regional view, Google Earth (below right) shows us the maximum AQI measured on the ground for whichever pollutant is dominating, either PM2.5 or ozone. Several readings in the Midwest are Code Orange (Unhealthy for Sensitive Groups) for both PM2.5 and ozone. Farther east, it is only ozone causing the Code Orange from Washington DC up to Philadelphia.

The rest of the country is relatively quiet in terms of air quality (AIRNow PM2.5 and ozone), except for some isolated fires in California, and a lingering plume of SO2 from the Kasatochi Volcano in Alaska. This plume is moving north and currently situated over North Dakota and western Minnesota according to the NOAA HMS text.

As shown in Adam's earlier post, good PM2.5 AQI levels were experienced throughout the eastern US. In Baltimore, the Oldtown ground monitoring station recorded PM2.5 concentrations that ranged between 5-12 ug/m3 (Good AQI levels: 16-39). A homogeneous boundary layer extended up to 1 km throughout today's timeseries. In order to show today's timeseries the color scale was reduced by a factor of 3.5, when compared with the lidar post of August 27th.

Code Yellow PM 2.5 conditions are continuing throughout the Midwest, continuing the trend described over the last few days (See the PM 2.5 hourly AQI animation from AirNow below). Code Yellow ozone is also present through much of Ohio and Indiana, with some in surrounding states as well.

There were no wildfires producing smoke visible on AOD or producing plumes in NOAA’s Hazard Mapping System for today in the Continental US. However, the Smoke Text Product indicates a small wildfire in Trinity County, CA, and also notes that elevated SO2 levels can be expected in Minnesota, Iowa, Wisconsin, Illinois, and parts of Michigan and Indiana that has been carried over from an eruption of the Kasatochi Volcano in the Aleutian Islands of Alaska nearly a month ago. The haze that this has mixed with can be clearly seen over Illinois, Wisconsin, and Michigan on the SSEC’s MODIS Today Terra Region 3 Image Below, with the corresponding IDEA Region 5 AOD:

Former Hurricane Gustav has now been downgraded by the National Hurricane Center to a Tropical Depression, and is expected to downgrade to a remnant low within 72 hours. There are, however, three additional named tropical storms in the Atlantic (From West to East: Hanna, Ike, and Josephine). Hanna is expected to make landfall on Eastern Florida, Georgia, and South Carolina on Friday, as described in this National Hurricane Center product:

Increased Ozone can be expected in those areas ahead of the storm as high pressure air causes relatively stagnant air. However, as the storm (or possibly hurricane by that point) passes through, ozone and PM 2.5 should be very low due to high winds, large amounts of rain, and minimal sunlight.

The big story on Labor Day is Hurricane Gustav, which made landfall at approximately 14:30 UTC (9:30 AM local time) this morning along the Louisiana coast, near Cocodrie, according to the National Hurricane Center. Prior to landfall, Gustav weakened to a Category 2 hurricane on the Saffir-Simpson scale, which was good news for residents of Louisiana. The ridge of high pressure over the eastern U.S. that Ray referred to yesterday will continue to push Gustav on a northwesterly course and slow its forward speed, increasing the threat of severe flooding in the Texas-Louisiana-Mississippi area over the next few days. The MODIS Terra true color image below of the USA7 region from the SSEC MODIS Today website shows the wide extent of Gustav as it made landfall. Hurricane Hanna is still out in the Caribbean and is expected to make landfall in northeastern Florida, Georgia, or South Carolina on Friday, and Tropical Storm Ike formed today in the central Atlantic. It’s shaping up to be an active Atlantic hurricane season, so all interests in the Gulf region and southeastern U.S. should keep an eye on the development and track of Hanna and Ike.

In other news, the haze across the Midwest that has been a persistent feature since last week continued again today. PM2.5 air quality was in the Code Yellow (Moderate) range across the Mississippi River Valley, the Great Lakes region, and the Ohio River valley today, due to the haze, as shown in the loop of today’s PM2.5 hourly AQI values from the AIRNow website (below on left). Ozone was mostly Code Green (good) today, except for a few scattered outbreaks of hourly Moderate conditions in the Great Lakes region, as seen in today’s loop of ozone hourly AQI values from the AIRNow website (below on right).

Today’s MODIS Terra true color image of the USA3 region from the SSEC MODIS Today website (below on left) shows the extent of the haze across the Great Lakes, Ohio River Valley, and eastern Midwest. NOAA’s Hazard Mapping System is reporting that smoke from fires in the western U.S. is mixed in with the haze. Elevated AOD from particulates associated with the smoke and haze is evident in today’s MODIS Terra AOD image for EPA region 5 from the NESDIS IDEA website (below on right). The hazy conditions are likely to persist at least another day, due to the building high pressure ridge over the eastern U.S. In addition, Code Orange (Unhealthy for Sensitive Groups) ozone levels are forecast across the southern Great Lakes region for Tuesday, as the ridge of high pressure brings sunny skies and light winds to the area. Areas directly impacted by Hurricane Gustav along the Gulf Coast will have very good air quality due to the steady rain, cloud cover, and gusty winds.