Current Air Quality and Smoke Monitoring
Air quality alerts and advisories (updated 6/18/2013):
The Carstens Fire started Monday, June 16, about 10 miles west of Yosemite in the Midpines area. As of Tuesday, June 18th, fire growth (or at least smoke production) appears to have slowed. Last reported acreage was 1600 acres, with 15% containment. Satellite imagery shows the plume spreading at least 100 miles to the north and south of Yosemite, though the high lofting of the smoke has limited impacts on air quality at the surface (Yosemite Valley graph, and webcam images below). Nighttime down-drainage winds are likely to continue cause some impact on air quality at the surface to the west of the fire's location, at least locally. Daytime winds are expected to continue switching from a northerly direction to a more westerly/southwesterly direction over the next day or two, bringing smoke more directly into, or at least over, Yosemite National Park.
The Mariposa County Air Pollution Control District has issued a Health alert for Mariposa County, including Yosemite National Park. More at:
Up-to-date webcam, satellite, and air quality information from sources in and around Yosemite can be found below:
Spring is usually the best time of year for smoke dispersion, and fire managers, when and where possible, try to take advantage of that good dispersion to get prescribed fire projects done before the stagnation and regional pollution (usually ozone) typical of summer months set in. Sometimes, smoke from local or regional fires also contributes. By the end of September though, ozone usually diminishes due to lower levels due to cooler fall temperatures, lower angle sunlight, and shorter days. Fires continue to occur in the fall before (or until) the rains come--as late as December in a dry year. Check back and scroll down to see the most current information on air quality and smoke impacts in Yosemite.
Yosemite NP monitors smoke/fine particles and ozone as part of a nationwide effort to protect air quality and public health. Current nationwide conditions are mapped below:
View of the Merced River Canyon, looking west from Yosemite Turtleback Dome, at 5,266 feet (1605 m) above sea level, toward the Central Valley. Direct links to other Yosemite webcams are below:
Yosemite Air Quality Monitoring: Fine particles/smoke at the Yosemite Valley Visitor's Center
The chart below plots both the 1-hour and running 24-hour average PM2.5 concentration, but only the 24-hour average should be used to compare with the standard. The standard is exceeded when the 24-hour concentrations go above 35 micrograms per cubic meter, as denoted by the line with the label NAT'L AMBIENT AIR QUALITY STANDARD. The background of the chart is color coded and relates to the EPA National Ambient Air Quality Standard for particulate matter, which is designed to protect human health.
A note on campfires and campgrounds: Some Yosemite campgrounds have many campsites and campfires. Emissions from many simultaneous campfires can degrade air quality on a local scale. This is especially true in the nighttime and early morning hours, when inversions trap and concentrate fine particles from those campfires near the ground, creating local conditions that are potentially unhealthy for sensitive individuals.
Ozone and human health in Yosemite: Because ozone pollution near the ground is usually only a concern on hot, sunny days, the ozone "season" runs May through September. Ozone is therefore rarely a human health concern in Yosemite during other times of the year. More on ozone and its health effects at AIRNow.gov.
Where in Yosemite is ozone usually a concern? Historically, data shows that ozone is worst in the Yosemite front-country (i.e., Wawona, El Portal, Crane Flat, and Camp Mather). At sites like these, ozone is often found at levels unhealthy for sensitive individuals (asthmatics or others with respiratory ailments). These unhealthy days often coincide with days that are unhealthy (Orange AQI) in the Central valley to our west, which is the primary source of this ozone.
In more sheltered areas like the Yosemite Valley and remote, high elevations areas like Tuolumne Meadows, ozone is usually much lower, rarely unhealthy even on most polluted of days.
When is ozone usually a human health concern in Yosemite? Highest levels of ozone on a given day usually occur in late afternoon and evening. If you have a respiratory condition, such as asthma, consult a doctor before exercising strenuously in front-country areas during late afternoon periods when high ozone might occur. Between the end of September/early October and May, ozone is usually not a human health concern in Yosemite.
Yosemite Ozone Monitoring:
Yosemite has been monitoring ozone at three sites for several years now: Seasonally at Yosemite Valley Schoolyard and Glacier Point, and year-round at Turtleback Dome.
The charts below plots both the 1-hour and running 8-hour average ozone concentration, but only the 8-hour average should be used to compare with the standard. The standard is exceeded when the 8-hour concentrations reach or go above 75 parts per billion, as denoted by the line with the label NAT'L AMBIENT AIR QUALITY STANDARD. The background of the chart is color coded and relates to the EPA National Ambient Air Quality Standard for ozone, which is designed to protect human health.
Ozone at Turtleback Dome west of the Yosemite Valley, overlooking the Merced River Canyon at 5,266 feet (1605 m):
Ozone at Yosemite Valley Schoolyard, near Yosemite Falls, at 3977 ft (1212 m) is no longer available in real time, but archived data can be found at: http://www.nature.nps.gov/air/monitoring/network.cfm
Online Tools to Locate a Fire Nearby
Did You Know?
Youth from local communities show off their artistic talent through poetry and art in Yosemite National Park’s Gateway Expressions Art and Poetry Contest. Families and park staff celebrate the creative talents of these local students through a special exhibit at The Ansel Adams Gallery in the fall.