The troposphere is the layer that is situated just above the surface of the earth; it extends for around 7 -20 km (4-12 miles) above sea level. Most of the atmosphere´s mass-70-80%, is in the troposphere and the rest is spread on the upper layers. All weather that occurs in the earth is developed in this layer. The temperature is warmer on the lower layer and the air becomes thinner and colder at higher altitudes.
Nearly all water vapor is in the troposphere and this is why most clouds are formed here. The atmosphere is composed of gases of which the most abundant are nitrogen 78%, oxygen 21%, argon 0.93% and traces of other gases, including carbon dioxide, nitrous oxides, methane and ozone.
The height this layer reaches varies with latitude, being greater at the equator with about 20 km (12.4 miles) and 7 km (4 miles) at the poles. It´s height also depends on the season, being lower in winter and greatest during summer. This layer is warmed up from the earth´s surface up. After the sun heats up the earth´s surface and oceans, this heat is radiated up
This layer contains from 75-80% or nearly 3.8625 x 10 to the 18 power kg from the 5.15 x 10 to the power of 18 kg which compose the atmosphere. Most of these contents are greater at the surface and decrease with altitude. In this layer, there is a substancial quantity of oxygen and carbon dioxide: used by living things for respiration and by plants for photosynthesis, respectively.
This layer also contains most of the water vapor, nearly 99% of all water vapor. Saturation vapor pressure decreases with altitude, keeping most water vapor at the surface of the earth, being greater at the tropics and lesser at the poles. This vapor forms part of the water cycle that creates rain and storms and the source are the rivers, lakes and oceans of the planet.
The troposphere contains the gases that permit living organisms to breath. Even though, it contains small amounts of carbon dioxide (0.04 %), it´s a sufficient amount that plants need for photosynthesis
Troposphere Gas Contents
Green House Gases
Water vapor and carbon dioxide are green house gases. Green house gases trap heat from the sun in the surface of the earth by reflecting heat back to earth.
Atmospheric pressure is greater at sea level and decreases with altitude. This is because the gases above the surface of the earth create weight it. The atmosphere is said to be in hydrostatic equilibrium, meaning that the weight on any given quantity of air is equal to the pressure above it.
This term refers to the heating of world regions by the sun. Sunlight warms the region of the equator more than the regions of the higher latotudes, causing convection air currents that distribute the thermal energy around the world. The Hadley Cell and The Polar Vortex are two convection cells that distribute thermal heat through the world, one creates air that rises at the equator and moves north and south then sinks at middle latitudes and travels at the surface to the equator.
There are two Polar Vortexes in the world, one in the north pole and the other in the south pole. These are low pressure areas that rotate counter.clockwise and clockwise, respectively. These vortexes span for around 1000 km (620 miles) in diameter and strenghten and weaken every year, creating polar fronts.
Earth Global Air Circulation
The temperature in the troposphere deacreases with altitude. The rate at twhich the temperature drops with altitude is called the environmental lapse rate (ELR). In the troposphere the ELR is of decrease in temperature of 6.5° C per every km in increased altitude.
Even though carbon dioxide is contained in small amounts, it has doubled since the 1900s and it´s believed that if the increasing rate continues, it could raise the temperature on the surface of the earth, provoking changing climate around the world, the melting of the polar ice caps and an increase in the levels of the earth´s oceans.
The Water Cycle
This process stars when the heat of the sun evaporates the water in the oceans, rivers, and lakes and everything that contains moisture. Vapor elevates into the sky and forms clouds. When the vapor has gained sufficient height, it condense again into water and falls down to the ground in the from of rain, hail or snow, refilling the bodies of water from which it evaporated.
Although, most of this occurs in the troposphere, some clouds called cumulunimbus clouds can take vapor into heights that reach the stratosphere.
This is the limit between the troposphere and the stratosphere-the next layer of the atmosphere. The tropopause is an inversion layer or a region where the decrease in temperature as air rises seases. Above this inversion layer in the stratosphere where the temperature remains constant with altitude then it increases. At the tropopause the lapse rate changes from positive to negative.
The Troposphere-lowest layer of the earth´s atmosphere
© 2018 Jose Juan Gutierrez