Since clouds were covering much of the East, let's talk about the West.
Today, Environment California Research and Policy Center released a report showing that the state's clean car standards have helped the air pollution due to automobiles to decrease by more than 85 percent since 1975.
They show that in 40 years people are driving much more but despite that, emissions of nitrogen oxides (NOx) and volatile organic compounds (VOCs) - the main precursors of tropospheric ozone formation - have decreased from 5,000 tons/day to 1,000 ton/day. But the report also shows that despite the progress, most of the population in California is still breathing in dirty air.
The report can be viewed/downloaded here.
Below I show figures 1 (left) and 7 (right) from the report. Figure 1 shows the average annual number of days exceeding the 8-hour average O3 standard in 10 years (1974-1984) and figure 2 shows the number of days in 2009 only.
Another figure from the report reinforces that although the ozone concentration has decreased over the years, unhealthy levels are still an issue.
Now, about the air quality today:
Following Ray's discussion on the poor air quality in San Joaquin Valley, haze continues degrading the visibility as we can see in these two webcam images: Sequoia National Park as of 7:30 PST(left) and Point Reyes National Seashore as of 07:45 PST (right).
MODIS AQUA RGB image also shows hazy conditions over the San Joaquin Valley and AIRNow AQI loop shows moderate to unhealthy levels of PM2.5 in the region.