Today’s air quality was very similar to yesterday’s, as seen in the loops of PM2.5 and ozone AQI values (below). Conditions persisted in the Code Green (Good) range, except for a few areas of Code Yellow (Moderate) PM2.5 in the southern Midwest, south Texas, and southern California.

One of the main reasons that air quality continued in the Good range today was the persistent stationary front that stubbornly remains draped across the East Coast, Gulf Coast, and Texas, bringing severe weather and flooding rains to much of the Eastern half of the country. Today’s MODIS Aqua true color image, overlaid with the current AQI values and 17:30 UTC synoptic analysis (below) shows the location of the stationary front and the associated cloud cover. What looks like haze in the true color image over west Texas and the Southwest is cirrus clouds.

It’s been a quiet day for air quality across the nation today, with both PM2.5 and ozone mostly in the Code Green (Good) range, as shown by the loops of AQI values (below). There were only a few scattered areas of Code Yellow (Moderate) PM2.5 in the Great Lakes region, south Texas, and southern California, and the Houston-Galveston-Brazoria area reported 8-hour average ozone values just into the Code Orange (Unhealthy for Sensitive Groups) range.

A stationary front that has brought steady rain to much of the eastern half of the country for the past two days was the main source of today’s good air quality. Today’s MODIS Terra true color image, overlaid with this morning’s synoptic analysis and the current AQI values (below, in Google Earth) shows the location of the stationary front and associated cloud cover.

In the image on the left below, I've superimposed a number of sources. The underlying RGB MODIS image is from MODISToday at UW, the yellow and green circles are PM indices from AIRNOW, and the numbers are from CoCoRaHs, which is a cooperative observer program that measures precipitation. While we see some Moderate PM readings around the Great Lakes, the bigger pollutant today was water as the rain which is moving through has left over an inch of rain in many areas (blue numbers are >0.75"). On the right image, the AIRNOW PM readings in the LA basin are superimposed over the MODIS Terra RGB this morning. Haze can be seen streaming westward over Santa Catalina Island.

There are a few stations in the US that have elevated PM today (mostly in TX, OH, FL) but there are no obvious sources seen from space. Much of the country is under cloud and severe flooding is forecast through KY, TN and AL. California has elevated PM near Sacramento but that, too, is under cloud. What looked to be a big smoke plume coming off South Carolina is nothing more than high cirrus clouds. We know that from the temperature of the infrared retrievals.

Today clouds were covering most of the US as we can see in Aqua MODIS image (top,left) making it almost impossible to visualize any event on the ground. PM2.5 levels were mostly good (top, right) with exception of California, Texas and the Northeast (from Pennsylvania to Maine) which presented moderate levels through most of the day.
Ozone levels were moderate to unhealthy (code orange) in California and Arizona (bottom, left) throughout the day. In the boundary East Montana/West North Dakota and also in Wyoming ozone reached moderate levels in the late afternoon.
NOAA HMS team reported smoke plumes coming from Central America and spreading out to Gulf of Mexico and North Pacific (bottom, right).

Good Air quality (measured in hourly PM 2.5 AQI) dominated the nation today, with some scattered Moderate AQI around Ohio and southern California for parts of the day. Ozone was quiet across the country except for southern California, where Code Orange levels were reached in the afternoon.

Most of the eastern half of the country was covered in weather systems, making any identification of smoke or other items difficult. That being said, no substantial plumes or haze were seen. This is in agreement with NOAA’s fire hazard mapping system, which does not show any smoke plumes in the U.S. There are, however, a number of large plumes in Central America, and it is possible that some of that smoke could move into the U.S. in coming days.

Air quality was mostly good across the country today, with a few isolated pockets of code yellow (moderate) air quality for PM2.5 and ozone (see AIRNow maps, below left and right, respectively).

Today’s Aqua MODIS true color image shows widespread clouds in the eastern half of the U.S. The corresponding Aqua MODIS AOD indicates relatively high levels of light extinction due to particles in Nevada. The NOAA Hazard Mapping System Fire and Smoke Product shows very little fire activity in the U.S., especially in comparison with recent weeks. (Mexico and Guatemala, on the other hand, continue to experience heavy fire activity).

As for the elevated AOD in Nevada, the Navy Aerosol Analysis and Prediction System shows us that this may be a dust event.