"Perfect Storm" Sparks California Air Quality Crisis

Via Cliff Mass Weather and Climate blog,

The Air Quality Health Crisis from the California Wildfires

The smoke from the California wildfires near Paradise, CA is producing the greatest air quality health crisis in the modern history of California.   Schools, universities, and sports events are being cancelled.

Although the terrible loss of life directly caused by wildfires in and near Paradise should not be minimized in any way, the health impacts of smoke will be profound, with millions of people being exposed to high concentrations of wood smoke. 

Hospitalizations will surely increase and some increase mortality of vulnerable populations should be expected.

MODIS satellite imagery on Thursday at noon.  Dense smoke filled the central valley of CA and moved directly over the Bay Area.

For me, it is also personal.  My son, a healthy young man of 27 living in San Francisco, is greatly feeling that smoke as is his similarly aged co-workers and friends.  If young, healthy individuals are being sickened, can you image the impacts of those that are vulnerable?

The current air quality conditions around the Bay area are pretty extreme (see below), with much of San Francisco and neighboring areas in the very unhealthy range (200-300).   Looking at data around the world, it appears that San Francisco now has worse air quality than any major metropolitan area in the world, worse than even Beijing and Mumbai.

But what really stands out is the longevity of this poor air quality event-- extending 7-9 days now for many central CA locations.    From my perusal of the air quality data of the Bay Area Air Quality Agency and other sources, this event is unprecedented in the 20 year period of data available.

The meteorological set up that has produced this air quality disaster started with strong offshore-directed "Diablo" winds driven by a large difference in pressure between the western interior (high pressure over Nevada) and the coast (lower pressure or trough)....see weather map below for the morning of November 8th. These strong winds initiated the fires and thus the smoke.

This was followed by a the building of high pressure aloft over the region (see upper level map for November 13th below)

and the development of modest high pressure over the intermountain west and a weak offshore pressure difference that produced light offshore flow, which moved westward through the Bay Area.  So there is no way for clean, Pacific area to reach the Bay Area in this pattern, and smoke from the Camp fires is continuously draining into the Bay Area.

But it is worse than that.  With high pressure aloft, there is sinking air in the middle troposphere (the lowest layer of the atmosphere that extends from the surface to roughly 30,000 ft), and that sinking aloft contributes to the development of a low-level inversion (temps warming with height)...something demonstrated by the radiosonde (balloon-lofted weather station) at Oakland yesterday morning.   Inversions acts as barriers to vertical motion of air.  The smoke is being held to a layer near the surface.

In short, we have had the "perfect storm" for dense smoke over the Bay Area and unfortunately this pattern is not going to shift in a radical way until next Tuesday.

But there is something positive to report.  The NOAA HRRR smoke system shows bad conditions today, but substantial improvement on Saturday as a weak push of marine air comes into San Francisco and the coast.  My son will be pleased.

Forecast of near-surface smoke at 5 PM today.

Some improvement on the coast and part of San Francisco Saturday at 4 PM.