heat traps – Southern California’s Fourth of July air-quality alerts ended Sunday afternoon, but the region’s heat wave threatens to keep soot and fine particles near the ground as winds weaken and onshore flow falters.
For the first time in days, the official air-quality alerts tied to the Fourth of July fireworks ended Sunday afternoon. But the relief came with an immediate catch: the heat that followed was strong enough to slow the normal clearing of pollution.
“It’s so hot, even the fallout from the fireworks is sluggish,” a National Weather Service meteorologist, Carol Ciliberti, said Sunday.
Ciliberti pointed to the atmosphere over Southern California as the reason. A high-pressure system driving temperature spikes is also suppressing much of the particulate matter and pushing it closer to the ground. she said. If pollution forms a layer aloft, that layer can get held down instead of mixing out and dispersing.
“If there’s a layer where there’s smoggy or particle stuff, then it’s suppressed closer to the ground, so that makes the situation worse,” Ciliberti said.
Normally, the region relies on onshore flow to help flush the air—winds moving west-to-southwest create an ocean breeze that pushes air away from the coasts. But Ciliberti said Sunday’s winds were weaker, meaning there wasn’t enough movement to carry the pollution out.
“If we had stronger onshore flow, that would help to disperse some of the fine particle pollution,” Ciliberti said. “That’s not happening.”
Even so, she said straggling celebrations were expected to continue Sunday night. They were not expected to create the same amount of pollution as the Fourth itself.
The fireworks aren’t arriving in a vacuum. This year’s smog and soot issues come on the heels of a late June warehouse fire in Boyle Heights that released extraordinary amounts of soot and smoke across Los Angeles County—on par with pollution generated by the previous year’s wildfires.
Saturday evening. the South Coast Air Quality Management District issued an alert for hazardous air quality due to the soot and particulates from fireworks. That alert ended at 3 p.m. Sunday for central and southern Los Angeles County, northern Orange County, and Riverside and San Bernardino counties.
July 4 and July 5 are traditionally two of the worst days of the year for Southern California’s air quality. according to the South Coast AQMD. With the heat set to remain the focus for Sunday and into the rest of the week. the question for residents is no longer whether alerts have lifted—it’s whether the air can clear fast enough on its own.
Southern California air quality Fourth of July heat wave soot particulates South Coast Air Quality Management District National Weather Service Carol Ciliberti Boyle Heights warehouse fire
So basically the fireworks stopped but the smoke just decides to stay? Love that for us.
I keep seeing “heat trap” like it’s some new thing but isn’t it just smog? The winds are weaker, okay… but why wasn’t anyone preventing the heat in the first place.
They said alerts ended Sunday afternoon and then “instant catch” like the soot is still hanging around, which yeah. But also that Boyle Heights warehouse fire is probably why everybody’s coughing. I don’t get how we can have fireworks AND a fire and everyone acts surprised.
Wait so if the winds aren’t pushing it toward the ocean, wouldn’t that mean just open your windows? Like people say stay inside but then it’s “onshore flow” so… just step outside and breathe slower? idk I’m confused.