her changes. Recently studies of the upper atmosphere, currently being conducted by earth satellites and missile probing, have shown these assumptions to be incorrect. The atmosphere has three well-defined strata.3 The layer of the air next to the earth, which extends upward for about ten miles, is known as the troposphere. On the whole, it makes up about 75 percent of all the weight of the atmosphere, because most of the solar radiation is absorbed by the earth’s surface which warms the air immediately surrounding it. A steady decrease of temperature with the increasing elevation is a mot striking characteristic. The upper layers are colder because of their greater distance from the earth’s surface and rapid radiation of heat into space. The temperatures within the troposphere decrease about 3.5 degrees per 1000 feet increase in altitude. Within the troposphere, winds and air currents distribute heat and moisture. Strong winds, called jet streams are located at the upper levels of the troposphere. These jet streams are both complex and widespread in occurrence. They normally show a wave shaped pattern and move from west to east at velocities of
150 mph, but velocities as
400 mph have been noted. The influences of changing locations and strengths of jet streams upon weather conditions and patterns are no doubt considerable. Current intensive research may eventually reveal their true significance.4 Above the troposphere to a height of about 50 miles is a zone called the stratosphere. The stratosphere is separated from the troposphere by a zone of uniform temperatures called the tropopause. Within the lower portions of the stratosphere is a layer of ozone gases which filter out most of the ultraviolet rays from the sun. The ozone layer varies with air pressure. If this zone were not there, the full blast of the sun’s ultraviolet light would burn our skins, blind our eyes and eventually result in our destruction. Within the stratosphere, the temperature and atmospheric composition are relatively uniform.5 The layer upward of about 50 miles is the most fascinating but the least known of the three strata. It is called the ionosphere because it consists of electrically charges particles called ions, thrown from the sun. The northern lights ( aurora borealis ) originate within this highly charged portion of the atmosphere. Its effect upon weather conditions, if any, is as yet unknown.
1Paragraph 2 _____.
A.The Definition and The Description of The Ions B.The Definition And The Description of The Stratosphere C.The Sun’s Rays D.Recent Studies of The Upper Atmosphere Versus Past Studies E.The Definition And The Description of The Troposphere F.The Composition of The Atmosphere
2Paragraph 1 _____.
A.The Definition and The Description of The Ions B.The Definition And The Description of The Stratosphere C.The Sun’s Rays D.Recent Studies of The Upper Atmosphere Versus Past Studies E.The Definition And The Description of The Troposphere F.The Composition of The Atmosphere
3The troposphere is the warmest part of the atmosphere because it _______.
A.contains a layer of ozone gases. B.about 42 degrees colder than on the ground. C.21% oxygen by weight. D.less than 1% of xenon by volume E.about 75 degrees colder than in Interlaken F.is warmed by the earth’s heat.
4The atmosphere con
