Layers of Atmosphere and Stratospheric Cooling

Global warming is a concept that we are all aware of by now. We know that it effects our atmosphere but the layers might differ in terms the effect they present and this might be foreign to some of us.

The layers of atmosphere can be seen below, it is the representation of NASA Global Climate Change Website. 

Figure 1 Atmospheric Layers

Global warming is often affecting each layer in different ways. Firstly, explaining the layers and their properties might help us to understand more about the effects.

Troposphere:

•          It holds all the air plants need for their photosynthesis needs and animals to breathe

•          Contains 99 percent of all water vapor and aerosols ( small solid or liquid particles suspended in the atmosphere)

•          Densest atmospheric layer

•          Most of the weather events happen in this layer

Stratosphere

•          Home to Earth’s ozone layer

•          Because of the UV radiation, the higher you go up to stratosphere, the warmer the temperature becomes.

•          Almost cloud and weather free

•          Exception : Polar stratospheric clouds and cumulonimbus thunder clouds

Mesosphere

•          Progressively becomes colder with the altitude

•          The top of this layer is the coldest place in the Earth System ( -85 Celcius)

•          Top of the mesosphere, the scarce water vapor, forms noctilucent clouds, the highest clouds of the Earth’s atmosphere (sometimes can be seen with naked eye)

•          Most meteors burn in here

•         Sound rockets can reach this layer

Thermosphere

•          Lowest part are the home for Aurora borealis, ionosphere layer

•          It is both cloud and water vapor free

•          The International Space Station orbits in this part of the atmosphere

Exosphere

•          This layer does not act like a gas, the particles here are tend to escape into space

•          No weather exists

•          Most Earth satellites orbit ib this part of the atmosphere

•          Actually there is no clear boundary

·         However, most of the scientists used what is called the ‘Karman Line’ to define a boundary.

(if you wish to learn more,  you can read more about Karman Line in here : https://astronomy.com/news/2021/03/the-krmn-line-where-does-space-begin)

Figure 2 Karman Line

Why Is There a Stratospheric Cooling and Tropospheric Warming?

Based on the several independent analysis measurements taken by radiosondes and satellite sensors, the troposphere has warmed up and the stratosphere has cooled down since mid- 1970s.

Troposphere (lower atmosphere) is warming from the bottom and the reason is radiation passing straight through atmosphere and is absorbed by earth’s surface, which warms up the surface and consequently warms up the atmosphere from beneath. And as air warms up the convection movement in the atmosphere dominates the temperature profile.

In contrast to this, the stratospheric layer is warmer at the top because of the solar absorption of O2 and O3. In a situation which this absorption by O2 and O3 do not occur, the stratosphere would be cooler at the top since it will only receive heat from troposphere, which means from below.

With the increase of greenhouse gases and the ozone depletion, the climate models started to include these two.

Change in lower stratospheric trends might indicate the ozone depletion recovery (although there are discussions about it) according to Rolf Philipona et al.’s study. It might be a likely driver for the explanation of how stratospheric cooling started to be observed as lower stratospheric warming via satellite measurements in 21st century.

These measurements are usually taken by radiosonde and satellites. They are both using what is called ‘remote sensing’ however radiosonde is usually a weather balloon, can be also a rocketsonde. 

Figure 3 Radiosonde 

With radiosonde , there are also a grounding system which ‘grounds ’ the data.

Figure 4 Radiosonde Ground System

This ground system device is utilized for synoptic (horizontal length scale of the order of 1000 km), research and military usage to provide upper air profile data.

Usually people get scared and feel panic when they find a Radiosonde fell on the ground. However, there is no need to be scared. It is usually not toxic or harmful yet in some cases (very rare occasion) the balloon might contain flammable hydrogen. In this situation stay away from it and call the local fire station for safe disposal procedure. 

Also there are instructions for returning it back after finding it.

Here is a sample one given by National Weather Service

https://www.weather.gov/upperair/radiosonde

 

I would like to add some insight about the topic before moving to references. This topic, the stratosphere situation and generally the atmospheric dynamics and the interaction between the layers are, in fact, really difficult and there are hundreds of modelling, calculation and discussion about them (like every science topic). Therefore, I wanted to explain these concepts in the most possible and brief way without mentioning the each model and satellite name etc.. Learning about the atmospheric layers really helps to understand the climate change effects and where they are occurring/ how they are effecting each other and us.

And if you would like to learn more, you can read The Role of Stratosphere in Climate article in the references. It is an article published in 1993 however it is written by researchers from NASA Goddard Space Center and it includes relationships among different layers of atmosphere in a wide perspective. I thought it might help if there is someone who is interested in these topics like me.

I hope you enjoyed it.

 

Thank you for reading!!

 

References

BIBLIOGRAPHY

[1]	C. M. ,. M. F. ,. P. J. P. T. ,. Rolf Philipona, "Radiosondes Show That After Decades of Cooling, the Lower Stratosphere Is Now Warming," Journal of Geophysical Research: Atmospheres, pp. 12509-12522, 2018.
[2]	D. .. R. a. A. LACIS, "THE ROLE OF THE STRATOSPHERE IN CLIMATE CHANGE," Surveys in Geophysics, pp. 133-165, 1993.
[3]	L. M. Corporation, "Lockheed Martin," [Online]. Available: https://www.lockheedmartin.com/en-us/products/meteorological-instrumentation.html. [Accessed 26 11 2021].
[4]	N. W. Service, "National Weather Service," [Online]. Available: https://www.weather.gov/upperair/factsheet. [Accessed 26 11 2021].
[5]	"Wikipedia/Synoptic Scale Meterology," Wikipedia, 10 June 2021. [Online]. Available: https://en.wikipedia.org/wiki/Synoptic_scale_meteorology. [Accessed 26 11 2021].
[6]	A. Buis/NASA, "Global Climate Change/NASA," NASA, 2 October 2019. [Online]. Available: https://climate.nasa.gov/news/2919/earths-atmosphere-a-multi-layered-cake/. [Accessed 24 11 2021].
[7]	E. Betz, "Astronomy," Kalmbach Media, 5 March 2021. [Online]. Available: https://astronomy.com/news/2021/03/the-krmn-line-where-does-space-begin. [Accessed 26 November 2021].