The stratosphere is the second layer of the Earth’s atmosphere, as we go upward from the Earth’s surface. The other four different layers of the atmosphere are – the troposphere, mesosphere, thermosphere and exosphere.
The layer of the stratosphere is found over the troposphere and beneath the mesosphere. The top of the stratosphere happens at 50 km (31 miles) height. The edge found between the stratosphere and the mesosphere above is known as the stratopause. The elevation of the base of the stratosphere differs with latitude and with the seasons, happening between around 8 and 16 km (5 and 10 miles, or 26,000 to 53,000 feet). The base of the stratosphere is around 16 km (10 miles or 53,000 feet) over Earth’s surface close to the equator, around 10 km (6 miles) at mid-latitudes, and around 8 km (5 miles) close to the poles. It is, somewhat, lower in winter at mid-and high-latitudes, and marginally, higher in the mid year. The edge found between the stratosphere and the troposphere underneath is known as the tropopause.
Let us study some more remarkable facts about stratosphere:
- The stratosphere comprises about 24% of the total atmosphere, containing, 19% of the atmospheric gases. The stratosphere consists about 90% of the ozone layer, present in its upper crust. This layer is responsible for absorbing the harmful UV radiations from the sun, by combining oxygen atoms to form the ozone molecules.
- As, the harmful ultraviolet rays get absorbed by the ozone molecules, the temperature increases on moving upward in this layer.
- There is variation in the temperatures in the stratosphere. At the top of the layer, the temperature has been recorded to be around 270 K, equivalent to, -3 degree Celsius or 29.6 degree Fahrenheit. This is because of the presence of the ozone layer in the top region, which absorbs the UV rays of the Sun. In the middle and lower regions of the stratosphere, the harmful UV rays are not able to reach, resulting in less temperatures.
- The stratified variations in temperatures in the different regions of the stratosphere were derived from the behavior of sound waves transmitted through the atmosphere, which are able to travel faster in warm air than in cold air.
- Stratosphere is composed of Atomic oxygen (O), found in the upper region. The ozone molecule (O3) is broken down by the UV rays into, atomic oxygen (O) and diatomic oxygen (O2). Methane (CH4) is also present in the upper region of the stratosphere. It can destroy the ozone molecules, by reacting with many hydroxy compounds (-OH).
- There is a low percentage composition of water vapors in this layer. So, the clouds are very rarely found in this layer. Despite the fact that the stratosphere has complex wind systems, still, there is no occurrence of violent storms. As, the air temperature in the stratosphere, slowly, increases with the increase in height, it leads to a stabilizing effect on atmospheric conditions in the region. Stability restricts vertical extensions of cloud and leads to the lateral spreading of highcumulonimbus cloud having characteristic anvil heads. This means that clouds are almost entirely confined to the troposphere below. This is the reason that airline pilots prefer to fly in the stratosphere.
- Air is about a thousand times thinner at the top of the stratosphere than it is at sea level. That’s why, jet aircraft and weather balloons are able to reach their maximum operational heights within the stratosphere, without encountering any turbulence.
- There are various types of waves and tides in the atmosphere that influence the flow of air in the stratosphere, even leading to its regional heating, sometimes. Some waves and tides transmit energy from the troposphere upward into the stratosphere and others pass on energy from the stratosphere up into the mesosphere.
- A unique kind of electrical discharge, called “blue jets”, occurs above thunderstorm in the stratosphere extending from the bottom of it, up to altitudes of 40 or 50 km (25 to 31 miles).
- Polar stratospheric clouds (PSCs) or nacreous clouds emerge in the lower stratosphere near the poles in winter, at altitudes of 15 to 25 km (9.3 to 15.5 miles) and appear only when temperatures at those heights fall below -78 degree Celsius.
- Some biological bacteria, live in the stratosphere. Some birds also reach the heights of the stratosphere (in its lower part) and can fly there. It’s our responsibility to protect the ozone layer to increase the oxygen and decrease the CFCs in the air. So, there is a need to plant trees, to protect our Earth from the harmful effects of ozone depletion.