It's April -- flowers blooming, ozone arriving

Posted by Mark Grossi on April 10, 2014 

Downtown Fresno on a murky air day.


Flowers are blooming, temperatures are spiking and ozone is returning in the San Joaquin Valley -- which breached the ozone threshold more than any other place in America last year.

From March to mid-April, people's lungs get a break between the soot season and the ozone season. Those who suffer with allergies may not get much of a break, though.

Either way, it's time to get in an ozone state of mind -- exercising outdoors early, consolidating errands in a vehicle, minimizing idling at drive-up windows.

This year, the ozone season started briefly with a single March exceedance in the tiny Kern County community of Edison, which is not far from Arvin, a notorious smog trap in past years. 

Now Edison is beginning to have problems again. There were exceedances Tuesday and Wednesday.

Heat, sunshine and pollutants create the ozone. Edison is downwind of the Bakersfield metropolitan area, so pollution plumes drift into the town.

The same phenomenon happens in the Fresno County community of Parlier. The same is true for Sequoia National Park's entrance station at Ash Mountain, which has some of the highest ozone exceedance totals in the country.

It's weird. Small towns and a national park along the Valley's east side seem to get the worst of it, even though you don't see much of a rush-hour traffic jam in any of these places.

The air quality has improved over the last decade. The Valley had its fewest-ever exceedances of the federal eight-hour standard last year. Yet it was still the highest total in the country.

Motorists continue to pay an extra fee on their vehicle registration each year after this region failed to meet the cleanup deadline for the one-hour ozone standard. But the local air district says the Valley achieved the standard last year and has petitioned federal authorities to lift that requirement.

Back to April. The month can be relatively free of ozone problems, if the weather stays cool and breezy. The month of May also can be cool and breezy, further delaying ozone season.

But when the brisk breeze stops and the mercury climbs, it's on.

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