Mesosphere

Two Layers of the Atmosphere

Based on chemical composition, the atmosphere is divided into two broad layers: the homosphere and the heterosphere. The homosphere extends up to the height of 56 mi. (90 km.) and is characterised by uniformity in chemical composition. It consists of three thermal layers, namely, the troposphere, the stratosphere, and the mésosphère. Each sub-layer is separated from the adjoining layer by a shallow transitional zone. The heterosphere has heterogeneous chemical composition, with layered structure, of nitrogen, oxygen, helium, and hydrogen, respectively. Generally, the atmosphere consists of five layers, namely, the troposphere, the stratosphere, the mésosphère, the thermosphère, and the exosphere. The thickness of these layers is slightly different around the globe, and also varies with respect to temperature and season. These five layers of the atmosphere act as safety blankets, regulating the Earths temperature and maintaining life forms in it.

The mésosphère is the third highest layer and is separated from the stratosphere by the stratopause and from the thermosphère by the mesopause. The top layer of the mésosphère is called the mesopause. The regions of the stratosphere and the mésosphère, along with the stratopause and mesopause are called the middle atmosphere. The mésosphère is the layer of the earth's atmosphere that is immediately above the stratosphere and below the thermosphère and is located from about 31 mi. (50 km.) to 50–56 mi. (80–90 km.) altitude above the earth's surface. Within this layer, temperature decreases with increasing altitude. The mésosphère spreads above the stratosphere from 31–50 mi. (50–80 km.). Temperatures in the upper mésosphère fall as low as minus 148 degrees F (minus 100 degrees C), varying according to latitude and season. Millions of meteors burn up daily in the mésosphère as a result of collisions with the gas particles contained there, creating enough heat to vaporize the falling objects before they reach the ground, resulting in a high concentration of iron and other metal atoms. The meteors, which fall to the Earth withgravitational force, burn due to the friction with the wind at this level. This layer protects the Earth from the falling meteors. It is characterized by a broad temperature maximum (near 32 degrees F, 0 degrees C) at its base, from which the temperature decreases to a minimum of about minus 130 degrees F (minus 90 degrees C) at the mesopause level. Mésosphère displays high wispy clouds in high latitudes during summer because of reflected sunlight from meteriotic dust particles.

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