Tuesday, July 17, 2012

The Fickle Finger of Fog

What a gorgeous day today turned out to be!  Stunning, it was, especially the afternoon and evening hours.  Based on this morning, which was socked in, all day yesterday, which was so pea soup-thick with fog it felt like it was raining, and the past 10 days, which were (you got it) foggy and cold, I would’ a bet money on more of the same.  What do they say, though: “If you don’t like the weather in San Francisco, wait a couple hours.”  That’s right; we’re gonna talk about the weather.

“The coldest winter I ever spent was a summer in San Francisco.”

The above one-liner is often attributed to Mark Twain, but its true origin is forever shrouded in mystery, much like the coast of northern California this July is shrouded in fog.  Lots and lots of fog.  For the final two weeks of June 2012, San Francisco basked in blue skies and above average temperatures (much of the rest of the county sizzled).  Then Mother Nature turned on the A/C.  When she did the mercury plummeted, the Golden Gate Bridge disappeared behind a wall of thick, puffy white, and Alcatraz was enveloped in a long, low arm of gray that stretched all the way to Berkeley and the Oakland Hills.  Like clockwork bands of tourists waiting for a cable car suddenly found themselves chilled to the bone.  You’d spot them huddled together in shivering masses at the corner of Bay and Mason or California and Van Ness - even worse at Chestnut and Laguna as they waited for the #28 MUNI bus to the bridge for a wet and windy walk across the span - no doubt lamenting their choice of sightseeing garb: shorts and tee-shirts instead of pants and a sweater (more like it sometimes…a parka).

Scientists classify fog into several different categories, the names dependant on how it was formed: radiation fog, advection fog, evaporation fog, upslope fog, freezing fog and ice fog.  The first two, radiation and advection, are the types we in the Bay Area know and love.  “Know” meaning deal with, and “love” meaning love/hate.

The following two paragraphs are from the National Oceanic and Atmospheric Administration (NOAA) website:

Radiation fog forms at night under clear skies with calm winds when heat absorbed by the earth’s surface during the day is radiated into space.  As the earth’s surface continues to cool, provided a deep enough layer of moist air is present near the ground, the humidity will reach 100% and fog will form.  Radiation fog varies in depth from 3 feet to about 1,000 feet, is always found at ground level and usually remains stationary.

Advection fog often looks like radiation fog and is also the result of condensation.  However, the condensation in this case is caused not by a reduction in surface temperature, but rather by the horizontal movement of warm moist air over a cold surface.  This means that advection fog can sometimes be distinguished from radiation fog by its horizontal motion along the ground.  Sea fogs are always advection fogs, because the oceans don’t radiate heat in the same way as land and so never cool sufficiently to produce radiation fog.  Fog forms at sea when warm air associated with a warm current drifts over a cold current and condensation takes place.  Sometimes such fogs are drawn inland by low pressure, as often occurs on the Pacific coast of North America.

Okay, I’m back.

Here in the Bay Area radiation fog is often called tule fog, named so after the tule grass of the California wetlands, and usually occurs inland during the fall and winter.  Our local advection fog is…well, it’s what we have now: big time summertime sea fog, or coastal fog.  Thank you, Mr. Pacific Ocean.

It may drive us crazy sometimes – the lack of sun, the wind, the damp and the cold - and we may long for the balmier climes that bless our inland brethren or those back east, but let’s face it: Life in San Francisco would be much different, maybe not as pleasant and certainly not as dramatic, without the fickle finger of fog.

First things first.  My apartment (and many like it) would probably come equipped with a humming, perhaps irritatingly noisy air conditioner.  At night it would be so god-awful hot I’d have to turn the contraption on, thus drowning out the mournful, hauntingly beautiful moan of the foghorn and the barking sea lions I sometimes hear as I fall asleep.  Next, we’d all have screens on our windows, which we don't need because the cool and the wind help keep mosquitoes and other pesky bugs at bay.  Finally, take away our iconic, usually brisk and blustery San Francisco sea air and after a month the city would turn stagnant, sticky, suffocating.  The pavement and the concrete would bake and before long certain parts of certain neighborhoods would smell…even worse than they do now.  Think of some of those urban centers back east during a prolonged heat spell (sorry New York City, but I’ve stayed with you in August).  Hell, then think of the winters.

Sure, during the summer months we might be able to regularly linger on Baker Beach without a blanket; brave the possible great white shark and swim at Stinson without a wet suit; more often enjoy a leisurely stroll on Ocean Beach without gloves, a scarf and a hat; even drive up and down the coast with the top down all the time.  We’d probably even witness more of those badass thunder and lightning storms (one of the things I miss about Ohio).  All this might seem a tantalizing scenario, but over time our unique and uniquely beautiful landscape would cease to be just that.  San Francisco is a great city, a world-class city, but it’s the surrounding wilderness and our close proximity to it, both terrestrial and aquatic, that seals the deal for me.

Big case in point.  The coast redwoods (sequoia sempervirens), the tallest trees in the world, absolutely adore the fog.  Probably wouldn’t thrive here without it.  The stately, handsome giants suck up most of their summertime moisture needs not through their roots from rain, but through their needles from the thick fog that collects in west-facing valleys open to the sea.  Without the 100" of yearly precipitation that fosters places like Muir Woods, Big Basin, Montgomery State Reserve and the Redwoods National Parks what else would disappear?  The western sword ferns that carpet a redwood forest floor, certainly; perhaps the Douglas fir, the redwood violet and trillium.  Probably much more.  Chop down a redwood forest and you're left with coastal scrub chaparral, fine in it's own right but nothing compared with an ecosystem practically endemic to California.

Our local cast of animal characters would be different as well, especially those that depend on the Pacific Ocean for food or call the big briny Home Sweet Home, because fog goes hand in hand with upwelling.  And upwelling, like summer in San Francisco, is way cool.

When seasonal winds on the California coast zip north to south, as they typically do during June, July and August, the earth’s rotation, in an example of what's known as the Coriolis effect, pushes surface water offshore.  To fill the void left behind, cold, nutrient rich water rises up from the depths, bringing with it all sorts of teeny-weenie phytoplankton, which blooms once it sees the light.  That’s upwelling, in a nutshell, but that’s not the end of the story.  Myriad forms of zooplankton follow the microscopic plant life; they chow down, also bloom, and present their calling card to the next creature up the food chain: a homely little crustacean called krill.  As upwelling continues the population of krill explodes, and with that explosion the table is set for a truly massive annual feeding frenzy that lasts through October.  Pelicans, grebes, cormorants, auklets, murres, phalaropes, puffins, black-footed albatross, sardines, herring, squid, salmon, tuna, harbor seals, sea lions, elephants seals, harbor porpoises, Dall’s porpoises, Risso’s dolphins, Pacific white-sided dolphins, killer whales, gray whales, humpbacks, fins and the big blues: they fly and flap and swim our way to feast on the abundance of food.  And not just a few: seabirds by the hundreds of thousands, whales by the hundreds!  As I write this there are reports of upwards of 40 blue whales hanging around Monterey Bay, with several others spotted out by the Farallon Islands.  Enormous pods of rampaging dolphins have already been seen, and humpbacks abound.  Yup, our part of the Pacific is amazingly fecund, especially during the summer (and especially this year, apparently).  If you’re into such things, and I am, there are few finer places on the planet to watch the show.  Fog is our friend.

And c’mon now, visually the F-word is oftentimes utterly enchanting - moody, changeable and alive, almost - and it usually never sticks around that long.  Couple of days at most (in the case of July 2012, a couple of weeks?), then the weather patterns change, the gloom retreats for a spell and the mercury rises to a (comparatively) balmy 64 or even (gasp!) 69 degrees.

The yin and yang of Mother Nature shall persist, though, just as it always does.  Sooner or later that first tentative whisper of fog will once again creep over the coastal hills, stretch a long, eager tentacle east across the center of the bay, and before long swallow the Golden Gate, partially or whole.  The temperature will nosedive 10 degrees; the foghorns blast to life.  Come afternoon the top of the Transamerica building and Coit Tower will no longer be visible, and by nightfall the entire city of San Francisco will be enveloped in a misty swirl of white and gray; a chilly wet that keeps the Buena Vista Café awash in tourists (and locals) craving a warm Irish coffee.  An eerie cloak that often makes me wonder if Jack the Ripper isn’t still alive and well and living in northern California, silently roaming the hills and alleyways of the City by the Bay.

I could go on, but it's now 7:00 in the evening, the wind has quieted, and it's just too beautiful outside.  In the Fort Mason District, where I live, the warmest part of the day, even.  I gotta get out for a nice long sunset walk by the bay while the gettin's good, before the you-know-what sneaks back into you-know-where for who knows how long.

Peter J. Palmer
July 2012


  1. i love you pp m?

  2. Love, love, love this! Your words created a picture in my mind that stuck with me long after I read this. I have always loved S. F. since I was a little girl. I read a book that took place there. Yet, I have never visited the city. Hope to soon! Love, your cousin in Fl., Dee