Wood County reporter. [volume] (Grand Rapids [i.e. Wisconsin Rapids], Wis.) 1857-1923, 1901-07-04
CHINOOK WINDS.
Fierce Gales of the Cakotas and the
Causes That Produce Them.

Causes That Produce Them,
o. ". Roberts, 4anktoa's weather
man, makes the following explanation
of the Chinook winds which swept
over the Dakotas and are among the
meteorological phenomena of the
northwest:
LAS the Dakotas are more or less
subject to the influence of what are
usually termed Chinook winds. 4
may be interesting to many to have
a general understanding OF the
character as well as the causes that
produce them. 1t is we'll known that
they are particularly noted for their
remarkable heat and extreme dryness
Mountain ranges are necessary for
their formation, hence only those
localities adjacent to such elevations
experience their effects. The princi
pal Chinook winds in this section OF
the country reach us from a westerly
direction. I will explain as clearly as
l can the formation of these winds.
I'VE all know that if we pour
oiCOHol III tuC pam VI our ndnQ ?
cooling sensation is experienced
Heat is required in evaporation. and
the cooling sensation is due to loss of
heat from our hand required in the
evaporation Of alcohol. According to
the law of conservation of energy. no
energy is wasted and the heat that is
required in evaporation will again be-
come liberated through the process nj
precipitation. This is an essential tact
in the explanation of the Chinook
winds. 1t is also we'll known that A
volume of air at given temperature
and pressure has a certain capacitv
for holding moisture, and that. if we in
crease the temperature, we thereby in
crease the moisture-holding capacity.
and, inversely, if we decrease the
temperature, we decrease it's capacity.
There must then be a point in this re-
duction process when the air will con-
tain maximum amount of moisture
for that particular temperature and
pressure, and any reduction below
this will cause part of this moisture
~ bC pI SSIpIIciISu. Ills DOlnC IS
known as the dew point.
THE moist air from the Pacific
moving landward becomes cooled by
coming in contact with the colder
mountain air, and still further by ex-
pansion due to elevation AS the air
becomes more and more elevated the
dew-point is finally reached and pre-.
cipitation takes place. AS before
stated, when precipitation takes place
latent heat is liberated, the tempera-
ture of the air is increased, it expands.
and, becoming still lighter, rises
higher until the dew-point is reached
and precipitation is resumed once
more. By this succession of Coolings
practically all the moisture is de-
posted on the westward side of the
mountain and when it reaches the
summit it is practically dry air whose
temperature is far above the normal
for that elevation. 1t is now ready fo-
its downward journey and it's tenn
perature is gradually increased, due
this time to compression, and when it
reaches the plains on the leeward
side of the mountain it is like breath
from furnace in the intensity of it's
heat. Like an unsaturated sponge,
it absorbs all the moisture in it's
path, causing the drifts of snow to
vanish as if by magic, yet not ap-
preciably increasing the volumes of
the rivers and creeks. "-Bismark,