The National tribune. [volume] (Washington, D.C.) 1877-1917, 1890-03-06

THE WEATHER.

Movements or the Atmosphere and Their Causes.
We have shown in previous article that the
solar heat IS the prtmuH mobile OF all atrnos-
pheric movements. But while this enormous
force IL al. peryading aud over-prcsent there
are others which have an influence that cannot
be neglected.
1t is now generally acknowledged in the
dynamics Of meteoroiogy that there are four
principal forces which must be taken into
account in a correct theory OF the winds. The
first arises from the greater specific gravity Of
tho atmosphere in some places than Others on
account of its condition as 10 temperature aud
the dew point; for when IL becomes heated in
any place or charged with vapor 10 greater
degree than at others, il becomes specifically
lighter; hence tho equilibrium Is destroyed;
there Is "A flowing together there Of the heavier
air on all sides, which dlsplaces the lighter air,
aud causes Ii TO rise up aud 10 flow out In
contrary direction.
A second force arises from the tendency
which the atmospere has under the influence
Of gravity when from any cause IL has risen
above The general level. TO flow TO places Of
lower level. These two forces generally pro-
ducc counter currents.
Again, when from any cauge particle Of mir
has been put in motion toward the y. or $.
the combination Of this motion with the Tota-
tory motion OF tho earth produces third
force which causes detection of the motion To
tho f. when this motion is toward the n, and
detection 10 the w. when 10 Is toward the S.
This is the same as one Of the forces contained
in La Places general equations Of tho tides the
analytical expression of which Is = sin cos
nur; being the latitude, n tho motion Of the
earth at the equator, the velocity of the
particle n. or s., and the radius Of the earth.
The fourth aud last force arises from the
combination Of relative T.. or w. motion Of
the atmosphere with the r0tatory motion Of the
earth. In consequence Of the atmosphere
revolving on q common axis with that of the
earth, each particle is impressed with "A centr-
fugal force which, being resolved into YER
tical and horizontal force the latter causes it
| TO assume q sphcrOidal form, conforming % the
| figure of the earth. But if the rotatory motion
| OF any part Of tho atmosphere is greater than
| that Of the surface Of the earth, or, in other
words, If any part Of the atmosphere has rela-
| tive eastcrly motion with regard to the carth's
| surface, this force is increased aud If ii has q
relative westerly motion, IL is diminished and
! this difference gives rise TO q disturbing force
which prevents the atmosphere being in q state
| Of equilibrium with figure conforming 10 that
| of the earth's surface, but causes accumua-
| ton Of the atmosphere at certain ATTITUDES and
| a depression at Others; and the consequent
difference in the pressures OF the atmosphere
| at these ATTITUDES very materially influence It's
| motions. This force is also expressed by one Of
| the terms of La Places equations, the analyti-
cal expression of which il sin II v 4, o being
| the relative eastern or western velocity of the
| atmosphere. Whatever direction u body moves
on the surface of the earth, there is force ars-
ing from tho earth's rotation which defects il
TO the right in the northern hemisphere but te
the ieG 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 Alst
the Well-estabiished facts that all storms move
from west to east in the northern hemisphere
and that the general trend of the paths of al
Lows is northeasterly. Also, that the circula
ton Of the air about q Low in the northern
hemisphere is from right to left, and the con
tIary in the case of High. In the southeri
| hemisphere these motions are reversed.