Why Bay Area air quality is poor, stagnant right now
Air quality across the Bay Area was “moderate” to “unhealthy” Thursday morning due to a high-pressure system trapping pollutants in the air over the region, meteorologists said.
The high-pressure system that brought sunny skies and seasonable weather to the Bay Area this week has also made the air stagnant, meteorologists said. A temperature inversion is to blame.
That’s when the air closest to the ground is cooler than higher elevations, allowing fine particles from car exhaust and fireplaces to stay trapped at the ground level.
“Typically we have onshore winds that are blowing and bringing in fresh marine air across the region,” said Roger Gass, a meteorologist with the National Weather Service.
“We have not had that because we’ve had this high pressure in place (that) at times allows some of those particulates to settle into the region and not see much movement,” he added.
Air quality ranged from “moderate” to “unhealthy for all” across the region, according to The Chronicle’s California Air Quality Map.
Aaron Richardson, a spokesperson with the Bay Area Air Quality Management District, said poorer air quality levels at this time of year weren’t unusual.
He said people using their fireplaces is the biggest source of fine particle pollution.
The Bay Area received a lot of rain in the past two months that helped clear the air, he said.
“But now with this highpressure system, pollution is building up a little bit,” Richardson said.
The Bay Area Air Quality Management District forecast the Bay Area would see air quality levels to be moderate in all regions Wednesday and Thursday, but no Spare the Air alerts have yet been issued.
Richardson said the district will continue to monitor air quality levels.