The DISCOVER-AQ project ended in Houston yesterday with a run of three days of increasing ozone and finally on Friday some elevated particulate pollution. But, the area was plagued much of the month with cloudy conditions and today a large band of clouds crossed the state of Texas. The NASA P3-B airplane returned to the East Coast today and went hunting fires in Georgia. The RGB from MODIS Aqua shows how clear it was across the country and the MODIS Aqua AOD shows uniformly low AOD across the country.
GASP, however, is showing high AOD east and west of the cloud band. Recall that GASP only has one visible channel and in the fall when vegetation senesces, a reddening artifact occurs and gives high AOD. VIIRS, however, shows the other extreme. There are no retrievals of AOD to speak of. Very perplexing trying to make a story out of the satellite picture today.
Update: Sunday September 29, 2013 at 17:00 EDT
Finishing off this post back in the Eastern Time Zone. The cloudiness that ran through the center of the US now has spread to cover much of the eastern half of the country. Driving through western Virginia this morning, I had the pleasure of fog accompanying me for a hundred miles or so.
One area of elevated PM is in the southern San Joaquin Valley. This arises from a nearly continuous 35-40 µg m-3 reading from Bakersfield in the AIRNOW reports. The reading in Visalia is about 10 µg m-3. It is not impossible to have such a gradient in the SJV as we saw in the second DISCOVER-AQ deployment last January, but usually it would show up on satellite. There is no unusual AOD in the areas and today's MODIS image looks very clear. It remains to be seen if this reading is real or an artifact.