San Mateo County CA Archives History - Books .....Chapter VII Climatic Peculiarities Of The Coast 1893
************************************************
Copyright.  All rights reserved.
http://www.usgwarchives.net/copyright.htm
http://www.usgwarchives.net/ca/cafiles.htm
************************************************

File contributed for use in USGenWeb Archives by:
Joy Fisher cagwarchives@gmail.com January 12, 2007, 3:14 am

Book Title: Memorial And Biographical History Of The Coast Counties Of Central California.

CHAPTER VII.
CLIMATIC PECULIARITIES OF THE COAST.

OUR uniform temperature throughout the year, on this coast, is largely due to
that great conservator of climate, the ocean, on our western border. During the
winter months, warm southeast winds prevail at intervals. The long winter
nights, with the lessened amount of heat from the sun, and consequent cooler
atmosphere, reduce the temperature of the southeast winds, coming from a warmer
region, and cause the condensation and precipitation of their moisture in the
form of copious showers of rain. This makes the so-called rainy season; during
which (especially, if there is much south wind) there is a general growth of
vegetation, as in spring in the Eastern States. Exceptionally dry seasons are
caused by a failure of these southerly winds in their seasons; when this occurs
the weather is colder, with more frost than in wet winters, when the south winds
prevail.

  In October, when the days are shortening and the resident of the Atlantic
States is hauling his "back logs" over the frozen ground, to protect himself
against the long, cold nights of winter, the farmer on the borders of the bay of
San Francisco is plowing his land for the next year's crop. Should the rains
begin in October, by the first of November the hills are green. The new season's
growth follows close upon the heels of harvest, and often overtakes the vintage.
Grain may be sown as early as October, or as late as April, and will perfect a
crop. Corn is rarely planted until the rains cease. In favorable locations the
japonica, the rose, and geranium will bloom all the year round.

  About the first of April the climatic condition is reversed. The days grow
long and warm, the south winds cease entirely, and are succeeded by the regular
northwest winds. The temperature of these winds from the ocean is colder than
the temperature on land; hence their moisture is dissipated instead of condensed
as it passes over the heated plains, and all clouds disappear altogether,
resulting in the absence of rains until the return of the southerly winds again
in autumn. From the above it will be seen why it is that the winters on the
California coast are comparatively warm, and the summers cool; in other words,
why we have an all-the-year equable climate, being a benefaction from the
all-generous ocean.

THE CAUSES OF OUR WET AND DRY SEASONS.

  As the summer sun, after it passes the equator in its northward march, heats
up the interior, or the Colorado desert, each day, rarefying the atmosphere and
causing it to rise over an immense area, thereby creating, or tending to create,
a vacuum, the surrounding air, and especially the cooler and heavier air of the
ocean, rushes in along the surface of the earth, to replace the attenuated;
lighter, rising air of this vast interior region. And thus it is that the
trade-winds of the Pacific ocean north of the equator, which, as mariners tell
us, blow six months in summer towards the southwest, are diverted inland near
the coast each day, with such force as to drive off, or in fact to dissipate
altogether all clouds, which might but for this powerful local cause tend to
gather and produce rain as in most other parts of the world. Now, as aqueous
precipitation is caused by precisely the same law, whether produced by natural
or artificial processes, it follows that if vapor is distilled or condensed into
liquid, artifically as in the still-worm, by passing from a heated state to a
relatively cooler state, or from a warm to a colder locality, then air currents
bearing moisture,-and all air currents do carry moisture, whether visible in the
form of vapor, or clouds, or not-must have their aqueous particles condensed by
the cold when passing from a warm to a relatively cool locality. Air currents,
moving from the equatorial regions toward either pole must have their watery
particles chilled and condensed by the increasing cold and by the intenser cold
overhead, and, if the process is continued long enough, precipitated, in the
form of mist, rain, hail or snow. This is the general law; and it is uniform and
inexorable in its operations, whether invoked by Nature or by man. And the
converse of this law is equally inexorable and uniform in its operations. If
relative cold condenses, relative heat dissipates.

  Herein then are found the causes, both of our wet and our dry seasons. The
heating up of the interior daily, while the sun is north of the equator, causes
a draft or suction of air-currents from where it is cool to where it is warm,
the result of which is the dissipation or dispersion of the moisture which those
air currents may carry. Therefore, the agencies which cause rain elsewhere are
wholly inoperative here so long as the sun is north of the equator. All winds,
and all fogs and clouds within the area of this all-potent local cause, to wit,
the suction of the daily super-heated desert, are subordinated to its action,
and the phenomenon of rain becomes, as a rule, impossible. And thus we have our
long, dry, but bracing, summers near the seacoast.

  But when the sun passes south of the equator it ceases to heat the desert, and
therefore causes but little or no draft, and then agencies which usually bring
rain the world over, are free to operate here. And thus we have our so-called
rainy seasons, i. e., seasons during which it becomes possible for rains to come
here, as they do elsewhere.

  Another incidental peculiarity of our daily wind currents may be noted in this
connection. These ocean breezes come up daily with the sun (or as soon as he has
heated the desert, say at nine or ten o'clock) and go down with the sun. The
earth, being heated on the surface, cools quickly, whilst the ocean, heated to a
considerable depth, cools slowly, and thus it is sometimes warmer in the night
than the land; and thus it happens that we have sea breezes by day, and land
breezes by night. These latter, however, are not regular. Sometimes these night
currents are off and sometimes on land, and sometimes there are none at all.

  The copiousness of our summer fogs near the coast are at least a partial
substitute for irrigation. These dense fogs are condensed whenever they drift
inland, by the relatively colder temperature of the land in the night; and
vegetation feels their influence and absorbs their life-giving moisture. The
effect of a few such summer nights equals a light shower of rain. This is why
all farm, orchard, and other crops will mature near the coast without
irrigation. This also, as has already been remarked, is why the dense redwood
forests thrive so wonderfully all along the immediate coast of northern California.

  In this respect, the climate of the coast counties differs from that of the
great and magnificent interior valleys of the State (outside of the influence of
these heavy fogs), where irrigation is necessary to produce a crop.

  The temperature of the sea-breeze is from 55° to 60° Fahrenheit. When the
ocean winds do not blow, the valley temperature, east of the mountain, ranges
from 80 to 90 degrees in summer, but this heat is neither dangerous nor
oppressive, as the air is dry and the nights are always cool. There is rarely a
day in winter or summer, when work out of doors cannot be performed without
physical discomfort; and in winter there are bright days in California which
would lead a traveler, coming from the ice-bound East, to believe that he had
really found a climate rivaling that of ancient Italia; and few would question
his belief.

TOPOGRAPHY AS AFFECTING CLIMATE.

  The topography of San Mateo county, to a considerable extent, governs its
climate. The mountain range which constitutes the backbone of the county, at a
point some fourteen miles from the straits through which the waters of the
Pacific ocean flow into the bay of San Francisco, rapidly decline in height, and
seem to lose themselves in the ocean. From this point to the Golden Gate, the
face of the ground is broken into low, rolling hills and sand dunes of variable
height. The northwest summer trade winds, accompanied by detached drifts of fog,
sweep over this depression, and give San Francisco its harsh but not unhealthful
summer climate.

  But the mountain range in San Mateo county turns the current of the
sea-breeze, and holds back the fog which crawls up the slope, and banks itself
along the summit of the mountains, being condensed by the relative cold of that
attitude, and also slightly obstructed, perhaps, by the trees and shrubs which
crown the crest of the range. This mountain fog bank is the condensed freshness
of the sea, out of which a cool breeze flows down the eastern slope of the range
to the bay shore, cooling the atmosphere of the plains and foot-hills, without
the disagreeableness or inconvenience of the propelling winds, or actual contact
with the fog. In other words, the morning sun warms the temperature of the air
of the valley below, which (as relative heat, according to an invariable natural
law, always does) rarefies and dissipates the fog and tempers the breeze as it
flows down the slope.


Additional Comments:
Extracted from:

Memorial and Biographical History of the Coast Counties of Central California.

Illustrated.

Containing a History of this Important Section of the Pacific Coast from the
Earliest Period of its Discovery to the Present Time, together with Glimpses of
its Auspicious Future; Illustrations and Full-Page Portraits of some of its
Eminent Men, and Biographical Mention of many of its Pioneers, and Prominent
Citizens of To-day.



HENRY D. BARROWS,
Editor of the Historical Department.

LUTHER A. INGERSOLL,
Editor of the Biographical Department.

"A people that take no pride in the noble achievements of remote ancestors will
never achieve anything worthy to be remembered with pride by remote
descendants."-Macaulay.


File at: http://files.usgwarchives.net/ca/sanmateo/history/1893/memorial/chapterv209gms.txt

This file has been created by a form at http://www.genrecords.org/cafiles/

File size: 10.5 Kb