January 5, 2013

0105 Weekend Edition: Air Quality Action Days across the US

As Patricia noted yesterday, Saturday was predicted to be an air quality action day in California and Utah, and the poor air quality did not disappoint. In December the EPA changed the AQI limits for PM2.5 down from 15 to 12 µg m-3 on an annual basis. The daily AQI remains at 35 µg m-3. The US AQI map is shown below and below that are two graphs of PM2.5 readings in Utah and the San Joaquin Valley. Both areas exceed the 24 hour averages and were those reading to occur throughout the year, they would be well above the exceedence levels. But the reason for the poor air quality at this time of year is poor dispersion. The boundary layer is quite shallow this time of year, especially over the snow covered Utah Basin. Both areas have seen significant population pressures over the last few decades so the amount of pollution is also rising. Starting next week NASA will study one of these areas, the San Joaquin Valley, as part of the DISCOVER-AQ mission. We will be blogging from Porterville, California, as that is the site where the UMBC lidars will be located. It should not be difficult to see haze of the magnitude of the graphs below.

Note the large variability in PM2.5 readings across the state of Utah.

Some people have a hard time visualizing the impact of these numbers. NOAA has given a clear day view of the Salt Lake Valley on the left and today's image on the right:

Update: Sunday January 6, 2013 18:00 EST

Three areas of the US have degraded air quality today. The Washington-New York I-95 corridor has elevated PM which reaches the USG level in a few locations (middle panel below). This is ahead of a front in relatively clear air. This is likely to move out by later this evening. Utah has very poor air quality again and it is code Red or Unhealthy levels throughout the day (bottom panel below). The concentrations continue to rise in Salt Lake City and Provo, Utah. California started with elevated PM but by 3:00AM a system has moved in with rain and the PM levels have dropped dramatically.

The poor air quality in Utah has made it to the Recommended Diaries list on Daily Kos.

Posted by Ray Hoff at January 5, 2013 4:10 PM
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