The atmosphere
Definition:
The Earth's atmosphere is an envelope of gas that surrounds the Earth and extends from the Earth's surface out thousands of kilometres, becoming increasingly thinner (less dense) with distance but always held in place by Earth's gravitational pull. The atmosphere contains the air we breathe and it holds clouds of moisture (water vapor) that become the water we drink. It protects us from meteors and harmful solar radiation and warms the Earth's surface by heat retention. In effect, the atmosphere is an envelope that protects all life on Earth.
Source: weather.gov
Troposphere
The troposphere begins at the Earth's surface and extends up to 4-12 miles (6-20 km)
high. This is where we live. As the gases in this layer decrease with height, the air
becomes thinner. Therefore, the temperature in the troposphere also decreases with
height. As you climb higher, the temperature drops from about 62°F (17°C) to -60°F (-
51°C). Almost all weather occurs in this region.
The height of the troposphere varies from the equator to the poles. At the equator it is
around 11-12 miles (18-20 km) high, at 50°N and 50°S, 5½ miles and at the poles just
under four miles high. The transition boundary between the troposphere and the layer
above is called the tropopause. Both the tropopause and the troposphere are known as the
lower atmosphere.
Stratosphere
The Stratosphere extends from the tropopause up to 31 miles above the Earth's surface.
This layer holds 19 percent of the atmosphere's gases but very little water vapor.
Temperature increases with height as radiation is increasingly absorbed by oxygen
molecules which leads to the formation of Ozone. The temperature rises from an average
-76°F (-60°C) at tropopause to a maximum of about 5°F (-15°C) at the stratopause due to
this absorption of ultraviolet radiation. The increasing temperature also makes it a calm
layer with movements of the gases slow.
The regions of the stratosphere and the mesosphere, along with the stratopause and
mesopause, are called the middle atmosphere by scientists. The transition boundary
which separates the stratosphere from the mesosphere is called the stratopause.
Mesosphere
The mesosphere extends from the stratopause to about 53 miles (85 km) above the earth.
The gases, including the oxygen molecules, continue to become thinner and thinner with
height. As such, the effect of the warming by ultraviolet radiation also becomes less and
less, leading to a decrease in temperature with height. On average, temperature decreases
from about 5°F (-15°C) to as low as -184°F (-120°C) at the mesopause. However, the
gases in the mesosphere are thick enough to slow down meteorites hurtling into the
atmosphere, where they burn up, leaving fiery trails in the night sky.
Thermosphere
The Thermosphere extends from the mesopause to 430 miles (690 km) above the earth.
This layer is known as the upper atmosphere. The gases of the thermosphere are
increasingly thinner than in the mesosphere. As such, only the higher energy ultraviolet
and x-ray radiation from the sun is absorbed. But because of this absorption, the
temperature increases with height and can reach as high as 3,600°F (2000°C) near the top
of this layer.
However, despite the high temperature, this layer of the atmosphere would still feel very
cold to our skin because of the extremely thin air. The total amount of energy from the
very few molecules in this layer is not sufficient enough to heat our skin.
Exosphere
This region is considered the very outer limits of the earth's atmosphere. Its lower boundary is often called the critical level of escape, where gas atoms are so widely spaced that they rarely collide with one another and have individual orbits. It is estimated to be some 400 plus miles (640 kilometers) above the surface.
Source for image:
As the outermost layer of our atmosphere, the exosphere is where a lot of space weather happens and is our first line of defense against cosmic rays, earthbound meteors, and asteroid impact, among other types of sky events.
As the outermost layer of our atmosphere, the exosphere is where a lot of space weather happens and is our first line of defense against cosmic rays, earthbound meteors, and asteroid impact, among other types of sky events.
There is so little density of particles in the exosphere that it can be difficult to determine where exactly the exosphere actually ends and outer space begins. While many particles that ascend to the exosphere are pulled back to lower levels of the atmosphere by Earth’s gravity, some airatoms and molecules manage to escape into space, yet they are so few and far apart that they rarely ever collide with each other.
Because the air in the exosphere is extremely thin, temperatures range quite drastically. Generally, the exosphere on the daytime side of the Earth can exceed 1,000 degrees, while things are far cooler on the nighttime side – only a few degrees above absolute 0.
It is in the exosphere that satellites orbit; in this environment, there is very little friction as compared to lower levels of the atmosphere, meaning it is the perfect place for equipment such as satellites to orbit with minimal disruption from molecular interference.
In the most technical sense, the upper limit of the exosphere is the last point at which Earth’s gravity still has any influence on particles. Using this definition, the upper exospheric boundary could be as high as 120,000 miles – which is halfway to the Moon.
Earth’s energy budget
Follow the link below for activities about Earth's energy budget:
The greenhouse effect
Source: http://globalwarming-facts.info/wp-content/uploads/1024px-Earths_greenhouse_effect_US_EPA_2012.png
How Do Greenhouse Gases Actually Work?
Changes in the global energy balance - global dimming
Global dimming is defined as the decrease in the amounts of solar radiation reaching the surface of the Earth. The by-product of fossil fuels are tiny particles or pollutants which absorb solar energy and reflect back sunlight into the space. This phenomenon was first recognized in the year 1950. Scientists believe that since 1950, the sun’s energy reaching Earth has dropped by 9% in Antarctica, 10% in the USA, 16% in parts of Europe and 30% in Russia – putting the overall average drop to be at an enormous 22%. This causes high risk to our environment.
Read more at What is global dimming?
Changes in the global energy balance - positive and negative feedback loops
Feedback loops: How nature gets its rhythms - Anje-Margriet Neutel
Source: http://cars-kill.weebly.com/uploads/4/5/0/5/45052885/179387390.jpg?447
Case study - negative feedback loop: Greenland
Source: Nagle, Garrett, and Briony Cooke. IB Course Companion. 2nd edition. Oxford: Oxford University Press, 2016. Print.
Enhanced greenhouse effect
Source: https://www.24point0.com/wp-content/uploads/2014/10/greenhouse-contributes-infographic-template.png
Synthesis and evaluation 1: task
Use the content of this post to plan and answer the following question: ‘Explain the complexity of the dynamic climate system and the spatial interactions of different processes and feedback mechanisms’. 10 marksUse markscheme on page 56 from the new syllabus guide (AO3)
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