DeSoto times. (Hernando, Miss.) 1879-1898, 1890-05-01
METEOROLOGICAL FACTS.
ihe Inherent Movements of the Atmosphsr,
and Their Cauaes


and Their Causes.
Solar heat is the primum mobile of all
atmospheric movements But while
tEis enormous force is all-pervading and
ever-present, there are others which
have an influence that can not be neg
lected.
1t is now generally acknowledged in
'he dynamics of meteorology that there
are four principal forces which must be
taken into account in correct theory
OF the winds. The first arises from the
greater specific gravity of the atmo-
sphere in some places than others on
account of its condition as to tempera-
tnre and the dew point; for when it be-
comes heated in any place or charged
with vapor to greater degree than at
others, it becomes specifically lighter;
hence the equilibrium is destroyed;
there Is flowing together there of the
heavier air on all sides, which displaces
the lighter air, and causes it to rise up
and to flow out in contrary direction.
second force arises from the ten
dency which the atmosphere has under
the influence Of gravity, when from any
| cause it has risen above the general
level to flow to places of lower level.
These two forces generally produce
counter currents.
Again, when from any cause particle
of air has been put in motion toward
the N or S. the combination of this
motion with the rotatory motion of the
earth produces a third force, which
causes DETECTION of the motion to the
Il. when this motion is toward the
N, and a detection to the W.
when 1T is toward the S. This is the
same as one of the forces contained in
La Places general equations of the
tides, the analytical expression of which
is . sin cos nur; being the latitude,
n the motion of the earth at the equator,
u the velocity of the particle N. or s.,
and p the radius of the earth.
The fourth or last force arises from
the combination of relative E. or W..
motion of the atmosphere with the
rotatory motion of the earth. In con-
sequence of the atmosphere revolving
on common axis with that of the earth,
each particle is impressed with centri-
fugai force, which, being resolved into
vertical and horizontal force, the latter
causes it to assume a spheroidal form,
conforming to the figure of the earth.
But if the rotatory motion of any part
of the atmosphere is greater than that
Of the surface of the earth, or, in other
words, if any part of the atmosphere has
relative easterly motion with regard
to the earth's surface, this force is in
creased, and if it has relative westerly
motion, it is diminished; and this differ
ence gives rise to a disturbing force
which prevents the atmosphere from
being in state of equilibrium with a
figure conforming to that of the earth's
surface, but causes an accumulation OF
the atmosphere at certain latitudes and
depression at others; and the conse.
ouent difference in the pressures of the
atmosphere at these latitudes very ma
terially influence its motions. This
force is also expressed by one of the
terms of La Places equations, the ana
lytical expression of which is 2 sin
r being the relative eastern and west
ern velocity of the atmosphere. What
ever direction body moves on the sur
face of the earth, there is force arising
from the earth's rotation which defects
it to the rightin the northen hemisphere,
but to the left in the southern.
Among the effects of these forces are
the development of the well-known
Highs and Lows, as shown on the daily
weather map. Also the well-established
fact that all storms move from west to
east in the northern hemisphere and
that the general tend Of the paths of all
Lows is northeasterly. Also, that the
circulation of the air about Low in the
northern hemisphere is from right to
left, and the contrary in the case of a
High. In the southern hemisphere
these motions are eversed.-National