California’s famous gray curtain of coastal fog is getting some very close scientific scrutiny. Bay Area researchers, teaming up with colleagues at five universities, are launching a statewide campaign to map the chemistry and behavior of Pacific coastal fog, from San Diego all the way up to Humboldt County.
The multi-institution project will roll out field campaigns along the shoreline, collecting fog droplets and installing towers and sensors that track temperature, humidity, wind and solar radiation. Early samples have already turned up traces of methyl mercury, prompting scientists to dig into how fog might be ferrying ocean-derived contaminants into coastal forests and food webs.
The work is backed by a roughly $3.7 million, five-year grant, according to the Heising-Simons Foundation. As outlined by the Heising-Simons Foundation, the funding is meant to generate data that decision-makers can actually use, from sharper fog forecasts to localized projections that help coastal managers prepare for change.
At UC Santa Cruz, atmospheric chemist Peter Weiss-Penzias and colleagues will lead the deep dive into what is riding inside those fog droplets, with a particular focus on toxic chemicals and biological molecules. In a campus release, UC Santa Cruz reports that the team plans to collect samples at about 15 coastal sites and analyze nutrients, algal toxins and trace contaminants in fog water.
How the fieldwork will operate
The Pacific Coastal Fog Research collaboration will use both passive "towering" collectors and active samplers. The passive collectors intercept fog directly as it rolls through, while the active units use fans to pull droplets through a smaller device. These will be paired with covariance towers and meteorological sensors to capture what the fog is doing and what it is carrying at the same time.
Partner campuses describe plans to deploy these arrays from the San Diego region north to Humboldt County, with different teams responsible for keeping equipment running and carrying out nightly sample runs. The networked approach and the role of student-built equipment in the campaign are detailed by San Francisco State University.
Some collectors will be placed near heavy-traffic corridors and oil refineries, so researchers can test fog’s role in moving urban and industrial emissions inland. As reported by The Mercury News, larger field deployments are scheduled to begin in spring 2026, giving scientists a shot at sampling across seasons and under different airshed conditions.
Why fog matters to forests, wildlife and health
Fog droplets are very good at scavenging gases and particles out of the air. Once that cocktail settles out with the mist, it can be taken up by lichens and plants, then move up through food chains. Previous field work has linked this pathway to higher levels of methyl mercury in coastal predators.
Studies show that ocean-derived methyl mercury can be delivered to land by fog, where it accumulates in terrestrial food webs and raises concerns for both ecosystem and human exposure. Materials from the USGS Pacific Coastal Fog Project stress how much more detailed fog chemistry data is needed to guide conservation planning and public health decisions.
On the technical side, the gear is not immune to everyday mess. Passive fog towers can pick up bird droppings and other debris, so project teams will compare those readings with data from cleaner, but more power-hungry, active collectors to make sure the chemistry checks out. In the lab, groups will dissolve lichen samples in nitric acid, then run targeted analyses for mercury and other metals to map how contamination from fog deposits varies across the landscape. UC Santa Cruz notes that student and engineering teams will help design, build and validate the active sampling systems.
A photo that ran with coverage of the project showed fog pouring over Joaquin Miller Park in the Oakland Hills in mid-December, a visual reminder that the mist these teams are measuring is the same stuff that shapes local parks and neighborhoods. The Mercury News paired the image with a field-team overview that links campus labs directly to the landscapes they will be studying.
Organizers say the resulting datasets, from droplet chemistry to detailed maps of fog frequency, are expected to inform decisions on pollution management, habitat restoration and health advisories as the climate shifts. The funders and partner institutions plan to release open datasets and forecasts so land managers and policymakers have concrete observations to work from. As described by the Heising-Simons Foundation, the ultimate goal is to turn complex fog science into practical local tools.
