Bismarck daily tribune. [volume] (Bismarck, Dakota [N.D.]) 1881-1916, 1901-03-25
aEtIeN = Ntls ..t1~tt5,W. - a II \ "4I. ~ @#aFISEEXEE
OF CHINOOK

WARM WINDS WHICH SWEEP.
OVER THE DAKOTAS ANALYZED
BY A WEATHER MAN, FROM "A
SCIENTIFIC STANDPOINT.
o. w. Roberts, Yankton's weather
man, makes the following explanation
of the chinook winds, which sweep
over the Dakotas and are among the
meteorological phenomena OF the
northwest: =
"As the Dakotas are more or less
subject to the influences of what are
usually termed Chinook" winds it
may be interesting to many to have a
general understanding Of the character
as we'll as the causes that produce
them. it is we'll known that they are
particularly noted for their remarkable
heat and extreme dryness, Mountain
ranges are necessary for their formal
ton, hence only those localities ada
cent to such elevations exprince their
effects. The principal Chinook winds
in this section of the country reach us
from a westerly direction. l will ex-
plain az clearly as I can the formation
OF these winds. f..
1--WE all know that If we pour alco-
rol in the palm of our hand that a cool
ing sensation is experienced. Heat
is required in evaporation; and the
cooling sensation is due to loss of heat
from our hand required in the evapo-
ration of the alcohol. According to
the law of the conservation of energy,
no energy is yer wasted, and the heat
that is required in evaporation will
again become liberated through the
process of precipitation. This is an
essential fact in the explanation of
the chinook winds. 1t is also well
temperature and pressure has a certain
capacity for holding moisture, and
that if we increase the temperature,
thereby increasing the volume, we also
increase the moisture holding capacity,
and inversely, if we decrease the tenn
perature, we decrease its capacity.
There must then be a point in this re-
duction process when the air will con-
tain a maximum amount of moisture
for that particular temperature and
pressure and any reduction below this
will cause a part of this moisture to be
precipitated. This point is known
as the dew point.
THE moist air from the Pacific NOV
ing landward becomes cooled by COM
ing in contact with the colder moun
tain, and still further by expansion
due to elevation. AS the, air becomes
more and more elevated the dew point
is finally reached and precipitation
takes place. AS before stated, when
precipitation takes place latent heat is
liberated, the temperature 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 success
sion of coolings practically all the
moisture is deposited on the windward
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. It is
now ready for it's downward journey
and it's temperature is gradually in
creased, due this time to compression;
and when it reaches the plains on the
leeward side Of the mountain it is like
a breath from furnace in the intens-
ity OF its heat. Like an unsaturated
sponge, 1t absorbes all the moisture
in it's path, causing the drifts of snow
to vanish az if by magic, yet not ap-
preciably increasing the volumes Of
the rivers and creeks"
a. q EFp 81 -- N-