THE SEASONS
Too great emphasis cannot be laid upon the futility, at present, of trying
to forecast the weather for more than a very few days in advance. Long
range efforts are not made by the Bureau because with its present limited
knowledge of the factors that control seasons and with the present limited
facilities for collecting data the process of looking into next month has
not been perfected, and the attempt to investigate next winter's weather
proves scientifically impossible.
As usual, fakers step in where science fears to tread. With goose-bones
(not their own) and hickory nuts they prophesy with all their might. And
if their prophecies come true, as sometimes they must, there is wide
rejoicing in the newspapers and the cause of science is set back by just
so much. But science cannot be thwarted in the end and every year new
discoveries are made, new speculations proved true or forever false, and
some time, doubtless, the weather will be predicted from year to year
with the same 85% accuracy with which the 36 hour forecast is now made.
Experimenting is worth the little that it costs, too, for to know when the
summer is to be dry or wet, hot or cold will be a boon to everybody and to
the farmer most of all.
One conclusion has already been reached by officials in the Weather Bureau
and scientists generally. It has been decided by long search through
creditable records, painstaking comparisons of averages coupled with the
most accurate investigations for half a century, that, on the basis of ten
years, our seasons do not change. That is, counting the decade as a unit,
our weather keeps to the same level of efficiency through the centuries.
This statement comes always as a blow. It always provokes argument and
citations of grandmother's blizzards. There is a great and universal
hesitation in believing that our weather is as good to-day as it used to
be. The good old times when there was a general debauch of snow and you
could skate all winter on anything but the Atlantic Ocean certainly appear
no more. As a matter of fact there has been a change, but it has been in
our memories. In grandmother's youth the trains,--if they had trains
then,--doubtless were stalled by a big snow for then they did not have
rotary plows. In father's day they may have had an unbroken winter of
sleighing. We couldn't now; sleighs are extinct. But in our time, in fact
every year, some record is being broken and the records go back a
respectable length of time.
For example in Philadelphia the most accurate records made by standard
instruments have been kept for 43 years. During this time the highest wind
velocity was recorded in 1878 (75 miles an hour). The greatest rainfall in
24 hours occurred in 1898 (5.89 inches). The lowest temperature was
registered in 1899 (6 degrees below zero); the highest in 1901 (103
degrees). The greatest number of thunderstorms for any one year took place
in 1905 when we had 51. As late as 1909 the heaviest snowfall ever
recorded at this station, amounting to 21 inches, occurred. And just a few
weeks ago (April 3rd, 1915) it snowed 19 inches in half as many hours. All
these items do not indicate a climate decreasing in virility very swiftly.
But there is more evidence yet that Philadelphia is experiencing the same
varieties of weather in about the same proportions. Diaries of observant
men running back to 1700 show that almost any kind of memory could be
founded on fact, that the same violent changes in temperature, the same
deep snows and unseasonable seasons that we endure to-day were noticed
then. To quote:
"The whole winter of 1780 was intensely cold. The Delaware was closed from
the 1st of December to the 14th of March. The ice was from two to three
feet thick." We despaired of ever living up to this until three years ago
when the same thing happened and sleighs crossed the river a little above
the city. And despite the new ice-boats!
"The winter of 1779 was very mild, particularly the month of February when
trees were in blossom."
"On the 31st of December, 1764, the Delaware was frozen completely over in
one night, and the weather continued cold until the 28th of March with
snow about two and a half feet deep."
"The winter of 1756 was very mild. The first snow was as late as the 18th
of March."
And so it goes. 1750 was mild; 1742 "one of the coldest since the
settlement of the country"; 1741 was intensely cold, 1725 mild, 1714 very
mild after the 15th of January, 1697 long, stormy and severely cold. The
upshot of it all is that February violets and April snows were just as
well known to General Washington as they are to us.
[Illustration: NIMBUS
_Courtesy of Richard F. Warren_
Nimbus is any cloud from which rain is falling, and the important thing to
know is how to judge from the formless thing how much longer it is to
rain. The wind is the surest guide. In this picture the nimbus cloud is
only that at the end of the cape. All the rest is torn stratus and
cumulus, which needs to condense a little further before it becomes
nimbus. This will likely happen because the cloud at the left is very
dark. The broken appearance denotes some wind. Rain does not fall from a
mottled sky nor yet a streaky one; the nimbus is uniform in appearance. In
summer a break in the nimbus will show a veil of cirro-stratus above. Just
nimbus by itself will not support much of a storm. In winter if the nimbus
is particularly seamless snow is about to fall.]
But though all facts point to the fact that the climate does not change in
a decade or a generation or a dozen generations, there is some comfort for
those who are not satisfied in knowing that it doesn't stay the same
forever. During the carboniferous times the poles were as warm as the
tropics and when the Ice Age came on it was very chilly everywhere. If one
might only live an eon or two he might then well complain of the changing
climate.
Climate, however, is one thing, weather another. The climate is the sum
total of the weather. Climate is as enduring as our Constitution, the
weather is as changeable as our city governments. No matter how proud a
scientist may be of the lasting qualities of the climate, he has to admit
that our weather, taken day by day or even year by year, is versatile in
the extreme. And the question he has set himself to solve is how to
explain the variations of the seasonable weather. He wants to find out why
all winters are not alike, and why no two successive springs are the same.
Then he will be on firm ground at last and able to make scientific
forecasts for the ensuing year.
The obvious thing was to find out as accurately as possible what had
happened and science's keenest eye was focused on records in the hope of
discovering fixed periods of warmth or wetness, cycles of cold and
drought. So far no cycles have been discovered that are beyond dispute.
Nothing has been found that cannot be contradicted successfully. This is
discouraging.
One of the most frequent starting places for investigators is the spots on
the sun. They found that periods of three, eight, eleven, and thirty-five
years should bear some resemblance; 1901 was eagerly looked forward to.
They wanted it to correspond with the remarkably cool summer of 1867. When
it started off in July with a temperature of 103 degrees, the highest ever
recorded in Philadelphia, they concluded that the sunspots were fooling
them. A connection between sunspots and weather has not been established,
therefore, although they are now known to affect the electrical condition
of the earth's atmosphere. Longer periods of observation will permit
comparisons that may yet define concurrent cycles of sunspots and weather.
A definite weather cycle has not yet been discovered, but one step in the
way has been cleared up. We now are pretty sure of one cause for unusual
single seasons of heat and cold.
There exist in winter great bodies of cold, dry air heaped up over Canada
and Siberia, which are formed by the greater rapidity of radiation over
land surfaces than over water. These mounds of cold air build up during
December, January, and February and form great so-called permanent areas
of high barometer. It is on the skirts of the Canadian high that the
smaller highs form which sweep over our country, giving us our cold waves.
Also in winter permanent lows form over the North Pacific and North
Atlantic where warm currents afford continuous supplies of warm moist air.
From the great Aleutian (Pacific) low spring most of the cyclones which
swing down below the border of the Canadian high, make their turn
somewhere in the Mississippi Valley, and then head for the Icelandic low.
It can be seen that if the Canadian high is a little stronger than usual
and spreads a little farther south, then the northern half of our country
will come more directly under its influence and we will experience an
unusually severe winter. As the storms are pushed south and as the cold
air pours into the northern quadrants the snow line is pushed south too.
Hence all abnormally snowy winters are caused by a strengthening of the
permanent Canadian high which may be central anywhere north of our Dakota
or Montana borders.
Conversely, if this high is weaker than usual the cyclones can cross the
country on a line farther north, there will be less snow, and the cold
waves that follow will be less severe or even non-existent.
In summer the reverse occurs. Great oceanic highs are built up over the
South Atlantic and South Pacific and a permanent low occupies the center
of our continent. The character of the season is determined by the
strength and position of these areas. The eastern states are affected
especially by the slow movements of the South Atlantic low. The puzzle is
why should these areas change their power and position, and if they must
change why don't they do it regularly? The puzzle will undoubtedly be
solved. These great centers of action will be plotted against and observed
from every vantage point by a thousand observers. A fascinating field for
scientific speculation opens.
At present our Government exchanges daily observations with stations in
Siberia, Canada, and the West Indies. The great storm-breeder, the
Aleutian Low, is watched from Alaskan shores. In the Atlantic the Bureau
needs stationary ships to record the growth and decline of the High over
the Azores. Knowledge of the wind circulation from this would inform us
whether our storms were to be shunted farther north and pushed somewhat
inland. A storm which is pushed to the left of its normal track increases
tremendously in intensity. Whereas a cyclone that limps slackly to the
right of its normal line loses intensity at once. It misses coil. In this
respect storms seem to resemble rattlesnakes.
The energy of the Azores High influences the number and destructiveness of
the West Indian hurricanes: the larger the area is the closer do the
hurricanes hug our shores and the more destruction do they accomplish.
The very sureness that the general average of the seasons is to be the
same enables us to guess pretty accurately for individual purposes as to
the kind of season coming next. A guess, let me add, is not a forecast. It
is a gamble and disapproved of by the Bureau, but until they supply us
with a basis for judgment we will have to go on guessing, for human
curiosity is as near to perpetual motion as the weather is to the lacking
fourth dimension.
One of these guesses is that if the winter has been a warm one the summer
will be cool, for the very good reason that the yearly average does depart
so slightly from the fixture. Unfortunately one hot summer does not mean
that the following summer will be cool. Certain sequences of the seasons
have been observed often enough to have been gathered into proverbs.
Everybody agrees that "A late spring never deceives." "A year of snow,
Fruit will grow." "A green winter makes a full churchyard."
Of the many hundreds of proverbs relating to the seasons a few are sage,
some outworn, and many sheer nonsense. Nearly all refer to the obvious
fact that one kind of season is followed by another rather unlike it, not
much telling what. And there, unsatisfactorily enough, they leave one. But
much is to be hoped for from the scientific explorations now in progress.
And until they are heard from few of us will realize how many seasonable
seasons we really enjoy.