atmoscience-blog

[atmoscience-blog]

Earth’s atmosphere

The atmosphere is a thin layer of gases, particles and aerosols surrounding the Earth and is retained by Earth’s gravity. This gaseous envelope helped to sustain life by protecting from deadly cosmic rays, intense ultraviolet radiation from the Sun, and even from heavenly objects like meteors. Earth’s atmosphere is predominantly a nitrogen (78.084%)-oxygen (20.946%) atmosphere and these two gases occupying about 99% by volume of the Earth‘s surface. In addition to these, the remaining 1% include minor and trace constitutes such as argon (0. 0.9340%), carbon dioxide (0.039%), water vapour (0.40%), ozone (0.000007%), carbon monoxide (0.00001%), hydrogen sulphide, ammonia etc. These gases cover 99.99% of the atmosphere by volume within 90 km of the Earth’s surface; even so 50% of the volume is concentrated in the lower 5 km range. Besides these gases, atmosphere also contains various suspended solid and liquid particles, known as aerosols.

Vertical structure of Earth’s atmosphere

 The atmosphere can be characterised by the variations in the temperature, pressure and composition with altitude. Based on the complicated vertical structure of temperature, World Metereological Organization classified the atmosphere into four different layers; troposphere, stratosphere, mesosphere and thermosphere. The closest layer to the Earth’s surface ( upto 16-18 km in the tropics, 10-12 km in the mid-latitudes and 8-9 km inthe poles) is troposphere.  This region contains nearly 80% of mass of the atmosphere and the strong vertical mixing leads to the cloud formation and its precipitation and results the weather changes. The temperature of the troposphere decreases with altitude at a mean rate (lapse rate) of 6.5°C/km. The boundary of the troposphere is a region of stable temperature, known as tropopause. The boundary of the troposphere is a region of stable temperature, known as tropopause. The upper layer of troposphere which extends up to about 50km is stratosphere. This layer is characterised by a small vertical mixing, which reduces the strength of the convective activities in that region. The temperature in this region increases with altitude at a rate of 3°C/km, due to the absorption of sunlight by ozone. The top of the stratosphere is known as stratopause. Mesosphere, the layer above the stratosphere from 50 km to 80 km , the temperature decreases with altitude with lapse rate of 2.75 °C/km.  The coldest temperature region in the Earth’s atmosphere is the Mesopause region and is about 100°C. The outer region of Earth’s atmosphere is thermosphere, which is a high temperature region, as a result of the absorption of short wavelength radiation by N2 and O2 mixing. Above 80 km, there are the large numbers of positively charged ions and free electrons, which is known as Ionosphere.

[atmoscience-blog]

Earth’s atmosphere

The atmosphere is a thin layer of gases, particles and aerosols surrounding the Earth and is retained by Earth’s gravity. This gaseous envelope helped to sustain life by protecting from deadly cosmic rays, intense ultraviolet radiation from the Sun, and even from heavenly objects like meteors. Earth’s atmosphere is predominantly a nitrogen (78.084%)-oxygen (20.946%) atmosphere and these two gases occupying about 99% by volume of the Earth‘s surface. In addition to these, the remaining 1% include minor and trace constitutes such as argon (0. 0.9340%), carbon dioxide (0.039%), water vapour (0.40%), ozone (0.000007%), carbon monoxide (0.00001%), hydrogen sulphide, ammonia etc. These gases cover 99.99% of the atmosphere by volume within 90 km of the Earth’s surface; even so 50% of the volume is concentrated in the lower 5 km range. Besides these gases, atmosphere also contains various suspended solid and liquid particles, known as aerosols.

Vertical structure of Earth’s atmosphere

 The atmosphere can be characterised by the variations in the temperature, pressure and composition with altitude. Based on the complicated vertical structure of temperature, World Metereological Organization classified the atmosphere into four different layers; troposphere, stratosphere, mesosphere and thermosphere. The closest layer to the Earth’s surface ( upto 16-18 km in the tropics, 10-12 km in the mid-latitudes and 8-9 km inthe poles) is troposphere.  This region contains nearly 80% of mass of the atmosphere and the strong vertical mixing leads to the cloud formation and its precipitation and results the weather changes. The temperature of the troposphere decreases with altitude at a mean rate (lapse rate) of 6.5°C/km. The boundary of the troposphere is a region of stable temperature, known as tropopause. The boundary of the troposphere is a region of stable temperature, known as tropopause. The upper layer of troposphere which extends up to about 50km is stratosphere. This layer is characterised by a small vertical mixing, which reduces the strength of the convective activities in that region. The temperature in this region increases with altitude at a rate of 3°C/km, due to the absorption of sunlight by ozone. The top of the stratosphere is known as stratopause. Mesosphere, the layer above the stratosphere from 50 km to 80 km , the temperature decreases with altitude with lapse rate of 2.75 °C/km.  The coldest temperature region in the Earth’s atmosphere is the Mesopause region and is about 100°C. The outer region of Earth’s atmosphere is thermosphere, which is a high temperature region, as a result of the absorption of short wavelength radiation by N2 and O2 mixing. Above 80 km, there are the large numbers of positively charged ions and free electrons, which is known as Ionosphere.