Deseret evening news. [volume] (Great Salt Lake City [Utah]) 1867-1920, 1906-07-03
THE TRADE WINDS
AND THE CYCLONES
interesting Scientific Facts About
The Greater Movements
OF the Air.
PLAIN PRINCIPLES EXPLAIN
s,,,n,c Flow of the Breeze and
The Rotary Motion OF the Deserts
Gigantic Whirls.


II was pure science at the University
,r,sh Yesterday. The professor DEM
U..r,ts5 that wherever the sun heats
-. earths surface the most there the
d heated. expands, and is forced
- IKE a cork in water, by the heavier
-. around It. Al the equator the heat
a ,sr moves A. degrees north and
=. Nth the season. the hot air ris-
tou'n NO. the sun is vertical, and the
h's t-,r, the north and the south
~ I'M and dsplaciug the heatc I
slr The earth moves most rapluiy al
tlI. ,1nstor. over 1000 miles per hour,
~ hat the air, which moves eastward
s,;-S Inc earth in It's rotation, Is ulere
,,,oying al that rate. AS me Wlnd
aovs In 10 the equatorial regions, u
isos behind the more rapidly moving
surface Of land or water az these
riaGes and appears as a wind blow
irr moi due south and due north, out
so1tbvest on the north and northwest
an he south OF the region Of greatest
heat. ,D,, ,,.,,.Ds
Tbsso are the trade winds. and they
tiou with great constaucy; but by the
,,r,e tbey reach the central zone %
rreatest heat the air has acquired the
Ind easterly motion Of the earth,
,rd a calm prevails, FOR the rising mir
n NO, felt as breeze. The zone 81 Gains
AL d 1 ID
latitude As the heated air gets cooled
hy rising. and still heavier by deposit
irr lts moisture. and by being COM
dressed laterally as It flows overhead
toward the temperate zones. Il sinks
The earth's surface and flows
toward the poles. j blows toward The
northeast in the northern and toward
Ire southeast IN IN southern hemi-
fphere. and is called the return trades
While zone OF variable winds lies
further north and south, where the Sc
trrn trades meet the polar winds We
i've IN the variable zone. Far north Is
The polar zone, IN which the winds blow
southwest In our hemisphere and north
vest in the southern polar zone.
WHAT CAUSES WINDS
The air at rest in the daytime Is the
densest and warmest next TO the eartAs
surface. and becomes thinner ana
cooler az successive attitudes, the aver
axe rate of cooling being one degree +.
for every 800 feet OF ascent. II. for
example, the sun warns the lower air
10 a temperature OF 90 degrees while
go feet above the desert sands. the
iemperature Is only 70 degrees, the sur
face air rising 800 feet viii be cooled
- ss.l. SO that the surrounding afr az
70 degrees will be heavier, and the air
that has risen will continue TO be fore
ID hIgher--a condition ~ unstable
equilibrium that viii exist whenever
ne air in rising 800 feet Is stu cur
rounded by air more than one degree
,,olsr than the heated air which began
"a kise. For n the air IN rising 800
fe,t comes 10 air Just one degree (ac-
ci-ately i.6) cooler than Itself 'vl-
5erty the air surrounding II VIII be or
The same weight as the air that has
risen. and a condition ~ stable equill-
frlum viii prevail with no tendency
10 further atmospheric motion. When
The surface dir Is Just enough warmer
than any layer above II % make up
for the change IN temperature that
would b. produced by the lower air
rising 10 the height Of any
above H., tho densltes are
potentially equal: not actually
EQUAL. FOR the lower Is compressed 10y
The weight Of that above g. and Is
heavier as well as warmer than that
above ANY further excess ~ surface
warmth brings about unstable equill-
hr.um; and any great excess VIII re-
suit IN A boiling ~ the air that
causes a whirlwind Of the c'cloni' or
der.
THE DESERT WHIRLWlND.
ONLY the desert can usually breed a
cyclone. and the Sahara is the breed
ing place Of the greatest and most de-
siructive ones. The afr must be- calm
10 begin with. for were II in motion
no part OF It would remain long enough
close 10 the ground 10 be greatly
warmed, The surface must be nat,
for we're u sloplng the lower air
would flow up the slopes as fast as b.
was a little heated. The surface must
he dry, for were IL wet much Of the
suns heat would be occupied In Cyap-
Grating the water and thus lost 20 the
lower air. Only on the desert. there
fore. can the sun readily warm the
surface air 10 such excess that the
lower layer may be compared 20 q film
81 oil balanced beneath a layer Of wa
ter As a little disturbance would
cause The two liquids 20 change places
30 with the very unstable equilibrium
~ TIE hot air on the desert, there is
strong uptuucht when the upseting
comes As me hot air wshes up.
me surrounding air flows IN. dust and
saa4 being blown 10 the center and
using with tte ascending current As
tht ar meets In the center, q rotary
Inouon Is established and the disturb
aiee becomes G. whirlwind. Forty feet
ron me center there may be only a
'Iee4e' Dat 10 the center the whirling
motion may become so strong that n
IaIIlel vacuum results. and objects are
,nol mo The center as II from d gun
lN small whiriwiuds the direction Of
l1e "hliling may be indinerently one
way or The other. according 10 the side
on which the indraught happens TO
ias' me center Such a whirlwlnd viii
,,op towards afternoon. when the sun
.'sN JUS power 10 supply the cause for
iI motion
THE REAL CYCLONE.
lhe larger cyl0nes are affected bv
NID ffffH'. rofnfffrs .rN ID .k.r. 80