Module 1: Themes in Physical Geography

Topic 3: WeatherUnit A : Atmospheric heating, motion

(winds) and moistureUnit B : Weather systems (air masses,

depressions, anticyclones) & their interaction with humans

Unit C : Hurricanes and their impact on people & property

A (i) Temperature

• Global energy balance

• The atmosphere is fluid. Transfer of energy is necessary because of uneven heating of globe.

• Vertical & horizontal heat transfer

• Heat is transferred vertically by air movement and horizontally by wind and ocean currents.

Meteorology is the study of atmospheric

phenomena (weather & climate). Vertical structure of

atmosphere

The atmosphere is an envelope of transparent, odourless gases held to the earth by gravitational attraction. Most of our weather happens in the first 16km ( it extends to 1000km).

• Divided into 4 distinct layers based on heat.

• Thermosphere• Mesopause• Mesosphere• Stratopause• Stratosphere• Tropopause• Troposphere• Sea Level

Troposhere

• Environmental Lapse Rate 6.4 C drop per 1000m up

• Earth’s surface heats air next to it by conduction, convection & radiation

• Pressure falls as effects of gravity decrease

• Wind speeds increase with height• Unstable layer as it contains most

of atmosphere’s water vapour, cloud, dust & pollution

• Tropopause is an isothermal layer – temperatures remain constant

Stratosphere

• Steady increase in temp. with height caused by:

• Concentration of ozone O3

• Ozone absorbs incoming ultra-violet (UV) radiation.

• Winds increase with height• Pressure decreases with

height• Dry• Protective shield against

meteorites

• Stratopause: isothermal layer

Mesosphere

• Temp. falls rapidly with height• No water, cloud, dust or ozone

to absorb incoming solar radiation

• Lowest temps. (-90 oC)• Strongest winds (3000km/hr)• Protective shield against

meteorites

• Mesopause – isothermal layer

Thermosphere

• Temp. rise rapidly with height (up to 1500oC)

• Increased proportion of atomic oxygen which , like ozone, absorbs incoming UV radiation

Atmospheric Gases

Energy in the Atmosphere

Short-wave solar radiation

(insolation)

Absorption (24%) of incoming radiation by wat.vap., CO2, ice & dust. Clouds absorb 3%

Clouds reflect (23%) radiation back into space – the thicker the cloud the more reflection

Earth surface causes reflection (4%) – oceans reflect only 10%, grassland 25%, fresh snow 85% (albedo)

Albedo is the ratio between incoming radiation and theamount reflected expressed as a %

SUN

100%

Scattering of radiation by dust particles (volcanoes, deserts) or by molecules of gas. Happens in all directions, some still reaches earth’s surface.

Earth’s surface

Diffuse radiation 21%

Direct insolation

24%

45% reaches earth’s surface

1% absorbed in stratosphere

Page 206 – 208 Questions1. What methods are used by meteorologists to measure the change in temperature

with height in our atmosphere?

2. By what 3 methods does the earth’s surface heat the air above it. Explain the difference in these three methods – you will have to research this!

3. Why do temperatures increase with height in the stratosphere?

4. Temperatures fall rapidly in the mesosphere, why is this?

5. Water vapour, carbon dioxide and ozone are found in very small amounts in our atmosphere, but yet each is vitally important, explain why.

6. What type of waves come directly from the sun?

7. What 4 astronomical factors determine the amount of incoming radiation received by the earth?

8. Explain why cloud types affect temperatures at the earth’s surface.

Homework continued……..

9. What 3 rolls can dust play in our atmosphere?

10. a) What is desertification?

b) How is desertification influenced by a change in albedo?

11. How are the terms scattering and diffuse radiation linked?

12. What percentage of incoming radiation actually reaches the earth’s surface and how does it get there?

13. Explain what happens to incoming radiation when it reaches the earth’s surface.

14. Why is the natural green house effect so important?

15. What is long-wave radiation also known as and what is it?