Atmospheric Structure IB SL

Atmospheric Structure There are four vertical layers within the atmosphere. Each has its own particular characteristics. The outer limit of the atmosphere is set at 1000km. The vast majority of our weather and climate is found within the lower 12km. Beginning at the earth's surface, the four layers of the atmosphere are...

Layers Bun Mayonnaise Lettuce Tomato Hamburger Bun The typical hamburger might look like this: bun, hamburger meat, tomato, lettuce, mayonnaise and bun. Hamburger Bun

Exosphere Thermosphere Mesosphere Stratosphere Troposphere Earth Name The Different Layers as they come in, also explain that the Exosphere is not really a layer but is the beginning of outer space. Troposphere Earth

Atmospheric Layers 8 layers are defined by constant trends in average air temperature (which changes with pressure and radiation), where the outer exosphere is not shown. Troposphere Tropopause Stratosphere Stratopause Mesosphere Mesopause Thermosphere Exosphere So far, we have seen that both air pressure and air density decrease with height above the earth Air temperature has a more complicated vertical profile. Look at this diagram, notice that air temp normally decreases from the surface up to about 11 km (36,000 ft) or 7 mi. This decrease in air temp with increasing height is due mainly to the fact that the sunlight warms the earth’s surface and the surface then warms the air above it. The rate at which air temp decreases with height is called Lapse Rate. The standard lapse rate is about 3.6F per 1000 ft of rise. Note this is only an average and is not always the case. There are times when air temperature actually increases with height. This condition is known as a temperature inversion. We use radiosondes to measure the day to day changes in the lapse rate.

1: The Trophosphere Decrease of temperature with height (6.4 degrees per 1000m). Increase in wind speeds with height. Fall in pressure with height. An unstable layer due to the presence of cloud, pollution water vapour and dust. The tropopause marks the outer edge of the troposphere and the limit to the earth's weather and climate.

Atmospheric Layers Tropopause separates Troposphere from Stratosphere. Generally higher in summer Lower in winter. So far, we have seen that both air pressure and air density decrease with height above the earth Air temperature has a more complicated vertical profile. Look at this diagram, notice that air temp normally decreases from the surface up to about 11 km (36,000 ft) or 7 mi. This decrease in air temp with increasing height is due mainly to the fact that the sunlight warms the earth’s surface and the surface then warms the air above it. The rate at which air temp decreases with height is called Lapse Rate. The standard lapse rate is about 3.6F per 1000 ft of rise. Note this is only an average and is not always the case. There are times when air temperature actually increases with height. This condition is known as a temperature inversion. We use radiosondes to measure the day to day changes in the lapse rate. Troposphere – Temp decrease w/ height Most of our weather occurs in this layer Varies in height around the globe, but Averages about 11 km in height. Figure 1.7

2: Stratosphere Temperatures increase with height in this layer, and it is here that ozone is concentrated, which absorbs UV radiation from the sun. Winds increase with height but pressure falls. The boundary is marked by the stratopause.

Atmospheric Layers Stratosphere Temperature inversion in stratosphere Ozone plays a major part in heating the air At this altitude So far, we have seen that both air pressure and air density decrease with height above the earth Air temperature has a more complicated vertical profile. Look at this diagram, notice that air temp normally decreases from the surface up to about 11 km (36,000 ft) or 7 mi. This decrease in air temp with increasing height is due mainly to the fact that the sunlight warms the earth’s surface and the surface then warms the air above it. The rate at which air temp decreases with height is called Lapse Rate. The standard lapse rate is about 3.6F per 1000 ft of rise. Note this is only an average and is not always the case. There are times when air temperature actually increases with height. This condition is known as a temperature inversion. We use radiosondes to measure the day to day changes in the lapse rate. Figure 1.7

3: Mesosphere A rapid fall in temperature with height, caused by a lack of water vapour, cloud and dust). Temperatures are extremely low and winds high. Its boundary is marked by the mesopause.

Atmospheric Layers Mesosphere Middle atmosphere – Air thin, pressure low, Need oxygen to live in this region. Air quite Cold -90°C (-130°F) near the top of mesosphere So far, we have seen that both air pressure and air density decrease with height above the earth Air temperature has a more complicated vertical profile. Look at this diagram, notice that air temp normally decreases from the surface up to about 11 km (36,000 ft) or 7 mi. This decrease in air temp with increasing height is due mainly to the fact that the sunlight warms the earth’s surface and the surface then warms the air above it. The rate at which air temp decreases with height is called Lapse Rate. The standard lapse rate is about 3.6F per 1000 ft of rise. Note this is only an average and is not always the case. There are times when air temperature actually increases with height. This condition is known as a temperature inversion. We use radiosondes to measure the day to day changes in the lapse rate. Figure 1.7

4: Thermosphere The outer layer of the atmosphere. A rapid increase in temperature with height, exceeding 1000 degrees.

Atmospheric Layers Thermosphere “Hot layer” – oxygen molecules absorb energy from solar Rays warming the air. Very few atoms and molecules in this Region. So far, we have seen that both air pressure and air density decrease with height above the earth Air temperature has a more complicated vertical profile. Look at this diagram, notice that air temp normally decreases from the surface up to about 11 km (36,000 ft) or 7 mi. This decrease in air temp with increasing height is due mainly to the fact that the sunlight warms the earth’s surface and the surface then warms the air above it. The rate at which air temp decreases with height is called Lapse Rate. The standard lapse rate is about 3.6F per 1000 ft of rise. Note this is only an average and is not always the case. There are times when air temperature actually increases with height. This condition is known as a temperature inversion. We use radiosondes to measure the day to day changes in the lapse rate. Figure 1.7

The troposphere is the lowest major atmospheric layer, and is located from the Earth's surface up to the bottom of the stratosphere. It has decreasing temperature with height (at an average rate of 3.5° F per thousand feet (6.5 ° C per kilometer); whereas the stratosphere has either constant or slowly increasing temperature with height. The troposphere is where all of Earth's weather occurs. The boundary that divides the troposphere from the stratosphere is called the "tropopause", located at an altitude of around 5 miles in the winter, to around 8 miles high in the summer, and as high as 11 or 12 miles in the deep tropics. When you see the top of a thunderstorm flatten out into an anvil cloud, like in the illustration above, it is usually because the updrafts in the storm are "bumping up against" the bottom of the stratosphere

The Stratosphere and Ozone Layer Above the troposphere is the stratosphere, where air flow is mostly horizontal. The thin ozone layer in the upper stratosphere has a high concentration of ozone, a particularly reactive form of oxygen. This layer is primarily responsible for absorbing the ultraviolet radiation from the Sun. The formation of this layer is a delicate matter, since only when oxygen is produced in the atmosphere can an ozone layer form and prevent an intense flux of ultraviolet radiation from reaching the surface, where it is quite hazardous to the evolution of life. There is considerable recent concern that manmade flourocarbon compounds may be depleting the ozone layer, with dire future consequences for life on the Earth. The Mesosphere and Ionosphere Above the stratosphere is the mesosphere and above that is the ionosphere (or thermosphere), where many atoms are ionized (have gained or lost electrons so they have a net electrical charge). The ionosphere is very thin, but it is where aurora take place, and is also responsible for absorbing the most energetic photons from the Sun, and for reflecting radio waves, thereby making long-distance radio communication possible.

Using Geography An Integrated Approach... Read through P206 and answer the following questions... What are 4 stages of the Earths’ atmosphere? What does each of the 4 parts of the atmosphere do? Why is it important that Earth has all 4 stages? Could we survive without 1 or more? Explain (10).