Fog by its very nature is insubstantial. Though often thick enough to veil entire mountains, it is always too flimsy to grasp. Fog may look and feel airy, but its wisps can hold a sizable amount of moisture. The idea of fog as a source of water is driving investigations into how this airborne river might be used by human and wildland communities.
Since 2005, Fernandez and his students have set up seven fog collectors around Monterey Bay. Two are located in the NRS's Fort Ord Natural Reserve, two on the CSU campus, and three in Big Sur. CSUMB itself is nearly adjacent to the Fort Ord reserve and, like the reserve, occupies lands once controlled by the army.
The devices are simple, but effective. Each consists of a one-meter-square frame with a double layer of plastic mesh stretched across the opening. Water particles in fog collect on the mesh, bead into larger drops, and trickle into a trough below. The design of the collectors follows an international standard.
A weather station located near each collector helps pinpoint the meteorological harbingers of fog. "This way we can know that, when there's fog, the humidity is this and the temperature just swung from a to b. We can come up with a set of metrics to determine not only when we have fog, but how much water that fog is delivering," Fernandez says.
Observing the collectors at work, however, requires being present at just the right times. In the years since he's deployed the devices around campus, Fernandez has observed them dripping water on only a few occasions. The majority of the collection occurs at night. "Not a time you want to be out in the middle of the chaparral when it's foggy," he says.
More recently, Fernandez has begun teaming up with researchers at NASA Ames Research Center near Mountain View, south of San Francisco. The space agency wants to know how to use satellite images to sense fog from space. The tricky part about fogcasting is distinguishing ground-hugging fog from high-altitude clouds.
The space agency funded the construction of three student-built collectors in Big Sur. All are located within less than a mile of one another on a ranch formerly owned by Candid Camera host Alan Funt. One was set up at an altitude of 2,000 feet, atop a bluff overlooking the ocean; the second is nestled downslope amid chaparral; and the third resides near sea level beneath the redwoods.
These collectors help NASA scientists verify whether or not the moisture their satellites detect is ground fog. So far, data from the satellite images concur with that of the water gauges about 80 percent of the time, at least at the high-elevation Big Sur site.
What isn't so clear is how much water arrives with each fog bank. Fernandez is closing in on the answer to this question as well by measuring fog-water production. His collectors are fitted with rain gauges that record the water collected by the trough every 15 minutes. "This gives us a more quantitative way to measure the amount of fog a region is getting at a given time," Fernandez says.
The collectors produce a phenomenal amount of liquid. One collector on campus can make about 3 liters a day; the record holder, perched above Big Sur, generates up to 7 liters per day, all of it generated by fog droplets that are only 10 to 40 microns in size — roughly the size of a single mushroom spore.
The Monterey Bay devices are built to standard design specifications thought to collect about half the moisture in fog. So Fernandez's data can be compared directly against data from collectors in places as far-flung as Morocco, the Canary Islands, Israel, and Chile. The water from many of these collectors is used for drinking and irrigation. But gathering data from standardized fog collectors around the world could clear up many more of the questions swirling around ephemeral fog. — KMW