Page 251 - NS-2 Textbook

246 NAUTICAL SCIENCES

(Ar) 0.9% exosphere
1 111~;IIII-<\~~ DIOXIDE (C02) 000
0.03%
WATER VAPOR (H20)
VARIABLE %

AND TRACES Of:

CARBON MONOXIDE (CO) 1
HElIUM (He)
HYDROGEN (H21 thermosphere
KRYPTON (Kr)
METHANE (CH!J
NEON (Ne) ionosphere
NITROUS OXIDE (N20)
OlONE (Oal
XENON (Xe)
70

mesosphere

chemosphere

What we call the "air ocean" is really a mixture of gases. By volume
it is composed of about 21 percent oxygen and 78 percent nitrogen,
with the remaining 1 percent made up of carbon dioxide, hydrogen,
helium, and traces of the rare gases such as neon, argon, krypton,
and xenon.

TROPOPAUSE
The tropopause is that transitional zone between the tro- The atmosphere consists of five principal layers. Each layer has
unique characteristics. Their exact boundaries are indistinct. The
posphere and the near void of the stratosphere. It starts
numbers shown here represent average heights.
just above the troposphere, at altitudes of from 5 to 11
miles, and it is divided into three overlapping areas:
tropical, extratropical, and Arctic tropopauses. The area
near the Earth's surface. Thus in winter the streams are
between 20,000 and 40,000 feet is of importance to air
over the temperate zones, where u.s. and Eurasian pilots
navigation. This is where the jet stream is located, a cur-
can take advantage of them. Huwever, in summer the jet
rent of air that moves swiftly from west to east around
streams move much farther north, out of most of the
the Earth. The jet stream is most prominent above the
main commercial air lanes.
extra-tropical and Arctic tropopause overlaps.
The jet stream was discovered in World War II, when
B-29 bombers flying about 4 miles high found great as-
STRATOSPHERE
sistance from westerly winds of up to 300 mph. Planes
were able to get into this stream and increase ground The stratospizere lies just above the tropopause and ex-
speed, shorten air time, and conserve fuel. Staying out of tends to an altitude of about 30 miles. There is almost no
these currents on the rehlIn trip also saved time and fuel. "\veather here because the air is too thin to create clouds.
The jet streams have nmv been charted seasonally as The temperature in the stratosphere drops much more
well as geographically. It has been found that these slowly than in the lower layer. In fact, the temperahlre
winds are strongest over Japan and the New England averages a fairly constant -40 degrees F to -50 degrees F
states. Three major jet streams move over the North and actually begins to get warmer in the upper limits. By
American continent in winter. One of them nearly blan- the time a pilot has reached the stratosphere, about three-
kets the United States. Information on the jet streams is fourths of the weight of the air is below the aircraft. Mod-
especially significant to commercial airlines, which use ern commercial aircraft seek to fly in the stratosphere
the information in plotting their flight paths. 'when not using the jet streams because there is so much
There is a direct relationship between the jet streams less air resistance. This makes much better fuel mileage
and lower ahnospheric air masses. Meteorologists have possible. Pilots also favor this flying level because there
found that the jet streams move with the cool air masses is no turbulence and they can fly at top speeds.