The Atmosphere Flashcards
Different layers of atmosphere
Troposphere
Stratosphere
Mesosphere
Thermosphere
Troposphere
Its upper limit may vary by an addition or subtraction of a few kilometers depending upon the temperature and nature of the terrestrial surface. Its thickness at the equator is greater than that at the pole. Its depth at the equator is 15km and at the pole is 8 km. The mass of troposphere is 70% of the atmosphere.
The temperature in the troposphere decreases with the increase in the altitude and falls to -56*c at the upper end of the troposphere.
Tropopause
The point at which the temperature inversion takes place . It is a narrow transition layer at the top of the troposphere at 10- 20 km of altitude in which the temperature starts suddenly to increase.
Stratosphere
It is situated above the troposphere and tropopause and constitutes the buffering strip and is responsible for the transition from one major environmental segment to the other. It is called stratopause and it is the region that is present immediately above the stratosphere. It marks the transition from the stratosphere to the next major region called the mesosphere. It reflects the sound waves from the earth back to the earths surface and thus plays a major role in radio and television broadcast. In the stratosphere–2oC is the temperature of the upper boundary of this region. The major components of the stratosphere are nitrogen, oxygen and ozone.
Mesosphere
It contains nitrogen, oxygen, ozone and nitric oxide as the principle species. The ozone is present in low concentration. On its top is the third transitional layer of the atmosphere called the mesopause. The major characteristic of mesosphere is the temperature. The temperature starts decreasing again with the start of mesosphere and the temperature profile exhibits a positive lapse rate. The temperature continues falling up to the end of the mesopause.
Thermosphere
The principal chemical species encountered in its composition are nitrogen, oxygen both in the atomic and molecular form O2+,O+, O-NO+. There is thus also a higher concentration of negatively charges ions and electrons in thermosphere. The condition of the atmosphere being highly rarified, the charged species in the thermosphere persist for longer period. Due to the presence ions in significantly higher concentration the region is called lono sphere.
Homosphere
It is the lower region of the atmosphere that extends from the earth surface to about 100 km of altitude. The basis of its nomenclature is homogenous composition of air in this region. There is a region of homosphere were most of the chemical reactions like formation of ozone, oxides of nitrogen etc. take place. This is called chemosphere.
Heterosphere
It extends from100 to 500 km of altitude and is situated just above the homosphere. In this region there is a high degree variation in the composition of the air and this heterogeneity forms the basis of its nomenclature. It includes the part of mesosphere and most of the ionosphere. Thus the air in this region contains a number of anions, cations and electrons. The ions constitute the charged belt that reflects the radio waves and helps in radio communication.
