Gnamma #88 - Fog Ontology
For the past six years I’ve lived near San Francisco, a place with a particularly charismatic fog presence. (“Karl”). In the subtle seasonality of coastal California, fog is also one of the better markers of time: the chilly and damp conditions of “Fogust” (now) contrast with the starkly clear bluebird days coming soon in November. People who say the Bay Area doesn't have seasons are just bringing the expectation of dramatic continental climates to a place that's running a different system.
Fog can be difficult to define, even, at a quick pass. Is it different from a low-slung cloud? At what threshold do we go from damp condensing air to… fog proper? The slippery, airborne phenomenon, a flavor of "occult precipitation"--fog challenges us because the word denotes a “thing” that really sits across a few spectra of environmental effects.
This graphical article by the New York Times from a couple years ago points to some of the high-level processes that make fog happen. Ocean waters along the coast of California, during the summer especially, are cold thanks to a high-pressure system driving winds from the northwest and an oceanographic process called upwelling. This brings cold waters from the deep up towards the surface of the coastal ocean. When warm and wet air flows over this cold ocean water, the air cools to its dew point and condenses into the wall of cloud and fog you can often see, looking westward from San Francisco. Going inland, the temperature gradient between the coastal ocean and the hot central valley of California sucks this foggy air inland, through whatever gaps are present in the coastal mountain ranges. And the biggest gap is the Golden Gate and the city of San Francisco. (Despite all its hills!) There is a dance of processes: the large-scale meteorological system, the physical oceanography, the flows of winds, and the geographic contours of the place. Then, as fog navigates the valleys and alleys of the terrestrial landscape, it gets “burned off” by warmer temperatures and turbulent mixing, finally pulling this delicate dance apart.
You can see why an environmental fluid mechanist would be excited about fog (oceans! wind patterns! turbulence!), but for those same reasons, meteorologists have 9-point lists required to try to predict fog’s presence. So even though seasonal patterns are dependable at some level, fog is notoriously difficult to predict. We instead might just check if the fog is here today.
Despite this difficulty, using fog as a potential water resource is an idea floating around various hydrologists’ heads. In foggy places around the world, people have “harvested” fog for centuries. Today, this is largely done with enormous meshes that catch the condensation and pull it down into collection basins. While this has potential in truly barren-arid and sparsely-settled places, a quick calculation of the infrastructure needed to harvest fog at large scales makes it economically infeasible in a place like San Francisco, where water use is high and real estate is pricey.
More interesting to me is how fog, as a form of water, would fit into management schemes as a water resource. Different types of freshwater are simpler for water management in different ways. Reservoirs have their fixed volumes and typically controlled outlets; rivers change their flow rates relatively smoothly and their geometries very slowly; groundwater can be difficult to visualize but it behaves in predictable ways when we have the soil and geology well-characterized. Fog’s delicate dynamism and ephemerality contrast against the ease of control in surface and sub-surface water resources on daily timescales. The seasonal statistical reliability is its only saving grace for management.
These challenges, however, point to some of the key assumptions underlying water resource management strategies. California, which so heavily depends on the slow release of melting snow from the Sierra Nevada mountains for its water planning over the dry summers, has faced historical challenges in water management from the fickleness of the snow season. (And, of course, how the water gets appropriated and used—"drought" is a constructed phenomenon.) Contemporary times, with a shrinking winter season and a more rapid snow melt in the spring, challenge expectations of fixed and easy-to-predict resources to use. This is nothing new: natural resource management is the art of turning something messy and patchy into a a simple and reliable commodity. But the less tangible and predictable the system, the more difficult it is to instrumentalize.
I've linked previously to the U.S. Geological Survey's updated water cycle diagram, but it's worth another visit: there's so much going on! Water is a truly three-dimensional, constantly changing presence across our little blue planet. Fog reminds us that it doesn't exist in a fixed way, like how we can find the ocean always in the same place. Water's natural trajectory is dynamic, more like a puddle evaporating on a hot day.
The title of this newsletter is inspired by one of my favorite lines from poet Ian Hamilton Finlay: “A garden is not an object but a process.” Fog is not an object at all: it challenges the fixed material view of the world that the engineering mindset loves. A water reservoir is more clearly an object, with its defined dimensions and properties. A river gets a bit more ontologically murky… not being defined by some specific batch of water but rather water’s flowing and mutable course. Snow is complicated mostly for its nuanced melting dynamics: rain falling on snow and refreezing change the makeup of snowbanks and their densities. But of all the forms of water and precipitation, fog is a fleeting flavor of air, likely the best described as a process—or the intersection of a few processes—rather than an imagined “reservoir in the sky.” I suspect that most of the conceptual model underpinning resource management thinking is the desire to turn the messy three-dimensional quilt of water in solid, liquid, and gaseous forms over the globe into a few well-quantified stocks and flows.
My point is that what fog is may just be fundamentally at odds with this engineering-first model of water management. We need serious leaps of faith and technology to wrangle fog into the controlled behavior we’ve grown to expect from water infrastructure. Or we need to change our expectations and embrace the assemblage of processes as the thing itself.
Shrouded,
Lukas
p.s. I quit the postdoc I had! I am navigating a search for other jobs to start essentially immediately in coastal engineering and science, and otherwise trying to enjoy some gasps of time to read and write and surf. I want to re-invest in this newsletter and have a slew of posts in the queue... because writing is the best way I know how to think and boy, do I love thinking. Let me know if my skills could be useful to you for anything: I could use some side gigs.