THE VARIOUS FORMS OF FOG

 

over SB
Fog over Santa Barbara and the harbor

Fog

The fog comes
On little cat feet.

It sits looking
Over harbor and city
On silent haunches
And then moves on

–Carl Sandburg

 

I’ve lived in coastal California for all of my 87 years, so you think by now I would have developed at least a tolerance for the fog which arrives each summer.  But I’m one of those unfortunate people whose moods are dictated by the weather.  Awaking to sunshine fills me with good cheer.  A gray beginning sets a similar mood for the morning.

Yes, I’ve heard the arguments – fog delivers at least some moisture in this driest of seasons during perhaps this most serious of droughts.  And the cloud cover protects plants from the desiccation by the summer sun.

I’m also aware that taking the perspective of a naturalist delivers me from being a victim of moods (moods are nice enough when they are cheerful ones).  I’ve spent the last few days doing research, reacquainting myself with my library including historical books like “Up and Down California,” Brewer’s fascinating account of doing a geographic and geological survey of the state in the 1850’s, and going a century back to the classical account of California’s coast by Richard Henry Dana in “Two Years Before the Mast.”  I’ve also been mining Google for gems of information.

Dana didn’t mention fog as he was more concerned about the winter when the anchored ship could be caught by a southeast storm gale and be blown ashore before they could set sail for the open ocean.

At the risk of sounding pedantic, here are some basic facts.  Our fog – advection fog – comes mostly in the summer months when the Northern Pacific High is in command.  That zone of high pressure that squats over the eastern Pacific, fends off storms that might come in from the north, and establishes summer wind patterns. In the late spring and early summer, the wind picks up speed and blows down the coast.  The wind displaces the warmer surface water causing an upwelling of the deeper, cold water.  When the warmer wind passes over the chilly water, the moist air condenses into tiny liquid droplets suspended in the air, forming fog.

from book
The movement of fog onshore on a typical summer day (“A Naturalist’s Guide to the Santa Barbara Region” Joan Easton Lentz.  Illustrator: Peter Gaede)

Often the fog is drawn inland by the low pressure lying over the hot the Great Central Valley.  The fog usually retreats back to the immediate coast where it may persist all day, and sometimes for days on end.  In Santa Barbara, those foggy days may be called May Gray or June Gloom. In Northern California the winds and chill air at Pt. Reyes makes it one of the foggiest places in the world with an average of 200 foggy days a year.

 

I favor those late summer and early autumn days of exoticdecreasing coastal fogs when the Pacific High begins to slowly shift south allowing for the possibility of an early rain coming down from the north.  Or when humidity sometimes moves north bringing the possibility of a thunderstorm and wonderful cloud effects.  Exotic weather heightens one’s senses.

northernI’m also reading about how coastal fogs along the north coast have allowed the redwood forest to persist.  Once, when the climate was much wetter, redwoods were common over much of the continent.  But as the climate became drier and cooler, the redwood forests retreated to a narrow band along the immediate coast of Northern California visited by ocean fogs in the summer.

I once read that sunny California has more fog than any other state when you consider that the coast in the summer is often foggy and in the winter, damp, ground-hugging tule fogs covback to sbering the Great Central Valley can blot out the sun for days on end until the next rain storm sweeps the fog away for a time.  The so-called radiation fog often follows the rain when the earth is both chilled and damp and the drier air above it condenses, forming fog.  I remember once driving across the Sacramento Valley at night and I could see that the fog came up to the cow’s belly, leaving its head in the clear.

Back to Santa Barbara: In his journal; ”Up and Down California” William Brewer writes on Tuesday, March 12 (1861).  “Still foggy and wet.  This weather is abominable – now for nearly two weeks we have had foggy, damp weather, tramping through wet bushes, riding in damp, foggy air, burning wet wood to dry ourselves, no sun to dry our damp blankets.  I find that it makes some of my joints squeak with rheumatic twinges.  Went out this morning, found it so wet that we had to return to camp”.

Five days later on Sunday Evening, March 17, he writes:  “We have had a clear hot day, after two week’s fog, and have improved the opportunity to dry our blankets and clothes, botanic papers, etc.”

I don’t recall in my four years of living in Santa Barbara of having a foggy spell in March.  What does ring true is the strength of the sun.  Even on foggy days, as the fog begins to thin one can feel the heat of the sun.  I remember being warned as a child, that I could be badly sunburned by the sun in a light fog.

I’m not sure about this, but it’s my impression that the west coast of the continents at our latitudes often have summer coastal fog.  In the case of Peru, Chile and Namibia in Africa, these are deserts with little or no rain, and no surface or groundwater.  A certain Namibian beetle sleeps with its hindquarters raised and in the morning shifts its position to allow the condensed moisture to run into his mouth for a drink.  Incas, living on the barren slopes off the west-facing Andes, after observing that pots under shrubs and small trees filled with fog drip, learned to string up nets made of small mesh which would sift drifting fog, collectinggreen up to a hundred gallons a day.

In the Bay Area where I lived, researchers measured in the rainless summer the equivalent of 10 inches of rain under the pines and eucalyptus along the ridgeline of the foggy Berkeley Hills.  I noticed how on my summer walks in the grasslands, yellow and dry by May, I could count on a circle of fresh green grass within the drip line of each tree.  The long narrow leaves of the eucalyptus and the slender pine needles did an especially efficient job of combing out moisture  from the drifting fog.

Harvesting fog

Why not string a series of nets along Twin Peaks in San Francisco?  Unfortunately such a meager harvest could only supply the needs of a small neighborhood. But there are small villages in the arid west coast of South America and elsewhere, where enough water was collected with fog nets to grow crops, irrigate orchards and have enough left over for personal use.

One such community is Bellavista, a village of 200 people on the dry slopes above Lima, Peru.  With almost no rain, no river, or groundwater, the village had to be served by anto  expensive water trucks from Lima.Lima

Conservationists Kai Tiederman and Anna Lummerich, working with a non-profit supported in part by the National Geographic, showed the villagers how to construct the fog catchers — nylon mesh stretched between poles.  The villagers did the heavy work, carrying sand bags 800 feet up the steep hill to stabilize the poles and to build pools to store the collected water.  With the wind blowing the heavy fog through the nets they can now collect 600 gallons a day.

end 1The newly-planted 700 tara trees will be able to eventually collect their own water.  Tara trees produce valuable tannin.end 2

Okay, I’m convinced.  Bring on the fog and no more grumbling about gray mornings.

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