TROPOSPHERE The troposphere is the lowest layer of Earths atmosphere. The troposphere starts at Earths surface and goes up to a height of 7 to 20 km above sea level. The term troposphere literally means turnover, meaning that in this region air mixes and constantly moves resulting in constant change called weather. Almost all weather occurs within this layer that why this is sometimes called as ZONE OF WEATHER. Air is warmest at the bottom of the troposphere near ground level. Higher up it gets colder. The boundary between the troposphere and the next upper layer is called tropopause.
STRATOSPHERE This layer is lying at about 20- 50 km. From the earth surface. The temperature in lower stratosphere remains the same but beyond, there is a gradual increase in temperature. Unlike the troposphere, there is no air mixing and no turbulence in this layer. Increase in temperature is due to the concentration of the gas ozone forming a layer called ozone layer. Ozone is a variant of oxygen compose of 3 atoms of oxygen. The boundary between the stratosphere and the next layer is called the stratopause.
MESOSPHERE Located within 50-80 km. from earth surface. The term literally means middle area. The temperature in this layer is decreasing. This is also the last layer with homogeneous air- air which is chiefly Oxygen and Nitrogen. Most meteors vaporize in the mesosphere. Some material from meteors lingers in the mesosphere, causing this layer to have a relatively high concentration of iron and other metal atoms. The boundary between the mesosphere and the next upper layer is called mesopause.
THERMOSPHERE This layer is lying beyond the mesosphere, specifically within 80-100 km. from the earth surface. Air in here is heterogeneous with varying amounts of Hydrogen and Helium. The actual temperature in the Thermosphere can reach as high as 2000º C! It is so hot here because nitrogen and oxygen in the atmosphere absorb a lot of radiation from space and convert it to heat. The boundary between the thermosphere and the exosphere above it is called the thermopause. The lower Thermosphere is called the Ionosphere; it extends from 80 to 550 kilometers above the Earths surface. Nitrogen, oxygen, and other particles in the Ionosphere absorb radiation from the sun and become electrically charged. Electrically charged particles are called ions, hence the name: the Ionosphere. These ions are important to radio because they reflect AM radio waves back to earth allowing for long distance messages to be sent.
THE THREE DISTINCT LAYERS EXIST IN THE IONOSPHERE1. D-layer – lowest layer containing the least amount of ions.2. E-layer – otherwise called the Kennelley-Heaveside Layer, the middle layer containing a higher concentration of ions.3. F-layer – also called Appleton layer, containing the highest concentration of ions. Intense ionization at daytime causes the absorption of radio waves instead of reflecting most of them back to the surface. At night, the ion concentration at the D layer falls because of the recombination of atoms. This makes the E and F layer very important for radio communication at night time. While listening to your radio sets at night, you will notice that it could pick up broadcasts from far off radio stations and even those from abroad. This is because of the absence of absorbing ions in the evenings.
EXOSPHERE Beyond 100 km. is the start of the earth’s outermost atmospheric layer, marking the beginning of the outer space. The air particles here are hotter than the ionosphere. The temperature are very high because of the incessant bombardment f cosmic rays. Density is very low the collisions between particles are extremely rare.
HEAT TRANSFERIN THE ATMOSPHERE
INSOLATION This is acronymfor Incoming SolarRadiation. Thisrefers to solarradiation reachingthe atmosphere andthe surface andbecomes utilized inheating his part ofthe atmospherenear the surface.
GREENHOUSE EFFECT The greenhouse effect is the natural process by which the atmosphere traps some of the Suns energy, warming the Earth enough to support life. The property is possible because of the so-called greenhouse gases which are responsible for the trapping of heat. Carbon dioxide and water vapor are the main greenhouse gases. Chlorofluorocarbons (CFCs) and Methane also to the greenhouse effect.
The Following Conditions Are Proof To The Heat-trapping Property Of These Gases:1. It becomes warm when days are too cloudy, especially when t s almost about to rain. This is due to the presence of air saturated with much water vapor.2. It becomes warm in cities especially in highly industrialized zones because of too much Carbon Dioxide as well as CFCs and Methane.3. Its warmer in areas with little or devoid of trees. Absence of trees would mean absence of natural sponges to absorb Carbon Dioxide in air. No trees would mean that most Carbon Dioxide remains in air.
RADIATION When water and landsurface are exposed to solarradiation, these bodiesabsorb heat back to the airdirectly above them in theprocess of radiation . Theland becomes heated firstthan the body ofwater, which explains whythe land radiates heat faster.Air above the land receivesthis radiated heat andbecomes heated also. Atnight, the land had alreadycooed but land and water isimportant and water are stillradiating heat. The unevenheating of are above theland and water is importantfor movements of air tooccur. Without such, therewould be no wind.
TURBULENT HEAT EXCHANGE The transfer of heat from theearth’s surface to the air directlyabove it is a combination ofradiation, convection andconduction. This combination ofheat transfer is called the turbulentheat exchange.